Fix dimension text rendering upside-down when drawn right-to-left

Normalize the dimension direction in both the SVG writer and the viewport decorator so text always reads left-to-right (or bottom-to-top for vertical dims) regardless of which anchor was placed first. Also guards against a pre-existing crash when two dimension endpoints project to the same screen position (zero-length vector passed to angle_signed). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add Force Parallel to Face constraint for parametric dimensions
2026-08-21 04:32:23 +00:00 · 2026-08-15 13:48:46 -05:00 · 2026-08-15 11:55:32 -05:00 · 2026-08-15 11:37:57 -05:00 · 2026-08-15 11:31:58 -05:00 · 2026-08-10 16:31:42 -05:00
23 changed files with 7027 additions and 62 deletions
@@ -5,7 +5,7 @@ FILE_NAME('Psets_BBIM_Annotation.ifc','2020-01-01T00:00:00',$,$,'Psets_BBIM_Anno
 FILE_SCHEMA(('IFC4'));
 ENDSEC;
 DATA;
-#1=IFCPROPERTYSETTEMPLATE('3VuPUwdCD2Qx3XDDRs0R1N',$,'EPset_Annotation','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation,IfcTypeProduct',(#4,#33,#29,#32,#3,#2));
+#1=IFCPROPERTYSETTEMPLATE('3VuPUwdCD2Qx3XDDRs0R1N',$,'EPset_Annotation','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation,IfcTypeProduct',(#4,#33,#29,#32,#3,#2,#41,#42));
 #2=IFCSIMPLEPROPERTYTEMPLATE('2P7JN79n96Q9pElZ83LKe4',$,'ZIndex','',.P_SINGLEVALUE.,'IfcInteger',$,$,$,$,$,.READWRITE.);
 #3=IFCSIMPLEPROPERTYTEMPLATE('1Wpx_r2xj1_9w5JpI0QRJy',$,'Symbol','',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #4=IFCSIMPLEPROPERTYTEMPLATE('3q0oxMUKP47vZ4jnyG$dDb',$,'Classes','Classes separated by spaces that end up in classes for this element in svg. Can be used to specify the text font size: small - 1.8mm; regular - 2.5mm; large - 3.5mm; header - 5mm; title - 7mm. By default regular size is used.',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
@@ -28,7 +28,7 @@ DATA;
 #21=IFCSIMPLEPROPERTYTEMPLATE('1UDakJ5_f7kBhggNSW4$h5',$,'SymbolsPath','Default symbols SVG',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #22=IFCSIMPLEPROPERTYTEMPLATE('0d53LEtgLDQxnv__NfgH7i',$,'PatternsPath','Default patterns SVG',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #23=IFCSIMPLEPROPERTYTEMPLATE('26qFNMv7nCHgU6Jd7Anga5',$,'ShadingStylesPath','Default shading styles',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
-#24=IFCPROPERTYSETTEMPLATE('0I9merLinF5Ap$aZwaclgm',$,'BBIM_Dimension','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation/DIMENSION,IfcAnnotation/RADIUS,IfcAnnotation/DIAMETER,IfcTypeProduct',(#25,#26,#27,#28,#30));
+#24=IFCPROPERTYSETTEMPLATE('0I9merLinF5Ap$aZwaclgm',$,'BBIM_Dimension','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation/DIMENSION,IfcAnnotation/RADIUS,IfcAnnotation/DIAMETER,IfcAnnotation/ANGLE,IfcAnnotation/PLAN_LEVEL,IfcAnnotation/SECTION_LEVEL,IfcTypeProduct',(#25,#26,#35,#36,#27,#28,#30,#34,#37,#38,#39,#40));
 #25=IFCSIMPLEPROPERTYTEMPLATE('1rL2AbQsXD8RbpoWH5pYOV',$,'ShowDescriptionOnly','Hide the measurement values and show only annotation description',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 #26=IFCSIMPLEPROPERTYTEMPLATE('0SVyOfB0rC2xNfdRYf3XvY',$,'SuppressZeroInches','Suppress 0 inch values in dimension annotation text (for example: 12'' - 0" -> 12'')',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 #27=IFCSIMPLEPROPERTYTEMPLATE('2bUmj458PBqPAtUoI3MXsb',$,'TextPrefix','Text to add before annotation measurement value',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
@@ -38,5 +38,14 @@ DATA;
 #31=IFCPROPERTYENUMERATION('CustomUnit',(IFCTEXT('Feet and Inches - Fractional'),IFCTEXT('Feet - Decimal'),IFCTEXT('Inches - Fractional'),IFCTEXT('Inches - Decimal'),IFCTEXT('Meters'),IFCTEXT('Decimeters'),IFCTEXT('Centimeters'),IFCTEXT('Millimeters')),$);
 #32=IFCSIMPLEPROPERTYTEMPLATE('0gjJzDYBX8P85qn1xcAOOo',$,'Reverse_List','',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 #33=IFCSIMPLEPROPERTYTEMPLATE('22TrcxF8jFNB4buSmzjGEF',$,'List_Separator','',.P_SINGLEVALUE.,'IfcText',$,$,$,$,$,.READWRITE.);
+#34=IFCSIMPLEPROPERTYTEMPLATE('1Kx4Pm9nR8vBwZqTs2uYeL',$,'Separator','Characters placed between multiple dimension values when CustomUnit has more than one unit selected (default: '' / '')',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
+#35=IFCSIMPLEPROPERTYTEMPLATE('3Nf6Qs1mT0pWxBuCvDyEzA',$,'SuppressZeroFeet','Suppress 0 feet in dimension annotation text (for example: 0'' - 3 1/2" -> 3 1/2")',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
+#36=IFCSIMPLEPROPERTYTEMPLATE('2Rg7Hn5jK4mLpNqOsVwXtY',$,'IsOrdinate','Show accumulated distance from the first vertex instead of individual segment lengths',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
+#37=IFCSIMPLEPROPERTYTEMPLATE('1XpRnKoT2sGuW7vYcZaMqb',$,'Anchors','JSON array of parametric anchor descriptors — one per polyline vertex. Each entry: {"guid": str|null, "type": "FACE"|"CIRCLE_CENTER"|"WORLD", "addr": {...}, "hint": [x,y,z]|null, "pt": [x,y,z]}',.P_SINGLEVALUE.,'IfcText',$,$,$,$,$,.READWRITE.);
+#38=IFCSIMPLEPROPERTYTEMPLATE('2YqSmLoU3tHvX8wZdaNrjc',$,'MeasureAxis','Axis along which distances are projected: X | Y | Z | TRUE | PERPENDICULAR',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
+#39=IFCSIMPLEPROPERTYTEMPLATE('3Ny31Go6T5Z9fh8j4yQC0p',$,'ForcePerpendicularToFace','When enabled the polyline is constrained to follow the face normal of the first anchor vertex so the dimension measures straight-line distance perpendicular to that face',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
+#40=IFCSIMPLEPROPERTYTEMPLATE('1LoNpKqR3sTuVwXyZaBcDe',$,'LinePosition','Absolute world-space coordinate (metres) of the dimension line along the horizontal offset axis (perpendicular to the dimension direction). When set, the dimension line is held at this fixed global position even if the measured geometry moves. When absent the line sits at the anchor points.',.P_SINGLEVALUE.,'IfcLengthMeasure',$,$,$,$,$,.READWRITE.);
+#41=IFCSIMPLEPROPERTYTEMPLATE('0FauxIsAnnotFaux0001aB',$,'IsManualDrawingReference','Marks this annotation as a manually placed drawing reference, exempt from automatic drawing regeneration.',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
+#42=IFCSIMPLEPROPERTYTEMPLATE('0FauxIsDocRefFaux001aB',$,'IsDocumentReference','Marks this annotation as pointing to an external document reference (not a Bonsai drawing camera).',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 ENDSEC;
 END-ISO-10303-21;
@@ -32,6 +32,7 @@ classes = (
    operator.ActivateModel,
    operator.AddAnnotation,
    operator.AddAnnotationType,
+    operator.AddElevationAnnotation,
    operator.AddDrawing,
    operator.AddDrawingStyle,
    operator.AddDrawingToSheet,
@@ -111,6 +112,16 @@ classes = (
    operator.ToggleDrawingCategorySelection,
    operator.OpenDocumentationWebUi,
    operator.FilterSelectedObjectsIfIntersectedByCamera,
+    operator.DrawParametricDimension,
+    operator.SetDimensionAnchor,
+    operator.RegenerateDimensions,
+    operator.DriveDimensionLength,
+    operator.RemoveDimensionAnchor,
+    operator.InsertDimensionAnchor,
+    operator.ClickNearestDimensionAnchor,
+    operator.MakeDimensionParametric,
+    operator.BakeParametricDimension,
+    operator.DebugDimensionClicks,
    prop.Variable,
    prop.Drawing,
    prop.Document,
@@ -172,11 +183,19 @@ classes = (
    gizmos.UglyDotGizmo,
    gizmos.ExtrusionGuidesGizmo,
    gizmos.ExtrusionWidget,
+    gizmos.GizmoAnchorHandle,
+    gizmos.GizmoDriveDimLabel,
+    gizmos.DimensionAnchorWidget,
+    gizmos.DimensionLinePositionWidget,
+    gizmos.DimensionDriveLabelWidget,
    workspace.LaunchAnnotationTypeManager,
    workspace.Hotkey,
 )


+_keymaps = []
+
+
 def menu_func(self, context):
    active_obj = context.active_object
    if active_obj:
@@ -196,9 +215,21 @@ def register():
    bpy.types.TextCurve.BIMTextProperties = bpy.props.PointerProperty(type=prop.BIMTextProperties)
    bpy.app.handlers.load_post.append(handler.load_post)
    bpy.app.handlers.depsgraph_update_pre.append(handler.depsgraph_update_pre_handler)
+    bpy.app.handlers.depsgraph_update_post.append(handler.depsgraph_update_post_handler)
    bpy.types.VIEW3D_MT_image_add.append(ui.add_object_button)
    bpy.types.VIEW3D_MT_object_context_menu.append(menu_func)

+    wm = bpy.context.window_manager
+    kc = wm.keyconfigs.addon
+    if kc:
+        km = kc.keymaps.new(name="3D View", space_type="VIEW_3D")
+        kmi = km.keymap_items.new("bim.click_nearest_dimension_anchor", "LEFTMOUSE", "PRESS")
+        _keymaps.append((km, kmi))
+        kmi_alt = km.keymap_items.new("bim.click_nearest_dimension_anchor", "LEFTMOUSE", "PRESS", alt=True)
+        _keymaps.append((km, kmi_alt))
+        kmi_ctrl = km.keymap_items.new("bim.click_nearest_dimension_anchor", "LEFTMOUSE", "PRESS", ctrl=True)
+        _keymaps.append((km, kmi_ctrl))
+

 def unregister():
    if not bpy.app.background:
@@ -211,5 +242,10 @@ def unregister():
    del bpy.types.TextCurve.BIMTextProperties
    bpy.app.handlers.load_post.remove(handler.load_post)
    bpy.app.handlers.depsgraph_update_pre.remove(handler.depsgraph_update_pre_handler)
+    bpy.app.handlers.depsgraph_update_post.remove(handler.depsgraph_update_post_handler)
+
+    for km, kmi in _keymaps:
+        km.keymap_items.remove(kmi)
+    _keymaps.clear()
    bpy.types.VIEW3D_MT_image_add.remove(ui.add_object_button)
    bpy.types.VIEW3D_MT_object_context_menu.remove(menu_func)
@@ -55,6 +55,14 @@ class ProductAssignmentsData:
        element = tool.Ifc.get_entity(bpy.context.active_object)
        if not element or not element.is_a("IfcAnnotation"):
            return
+        # Document-reference annotations link to an IfcDocumentInformation, not a product.
+        if tool.Drawing.is_document_reference(element):
+            for rel in element.HasAssociations:
+                if rel.is_a("IfcRelAssociatesDocument"):
+                    doc = rel.RelatingDocument
+                    if doc.is_a("IfcDocumentInformation"):
+                        return doc.Name or "Unnamed"
+            return None
        for rel in element.HasAssignments:
            if rel.is_a("IfcRelAssignsToProduct"):
                name = rel.RelatingProduct.Name or "Unnamed"
@@ -312,6 +320,9 @@ class DecoratorData:
            "StartArrowSymbol": "",
            "ShowEndArrow": True,
            "EndArrowSymbol": "",
+            "BorderOffset": 8.0,
+            "AutoStartPosition": "",
+            "AutoEndPosition": "",
        }
        obj_pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Section") or {}
        pset_data.update(obj_pset_data)
@@ -331,6 +342,9 @@ class DecoratorData:
                "symbol": end_symbol or "section-arrow",
            },
            "connect_markers": pset_data["HasConnectedSectionLine"],
+            "border_offset": float(pset_data["BorderOffset"]),
+            "auto_start_position": pset_data["AutoStartPosition"] or "",
+            "auto_end_position": pset_data["AutoEndPosition"] or "",
        }

        cls.data[obj.name] = display_data
@@ -799,19 +813,24 @@ class DecoratorData:
        pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension") or {}
        show_description_only = pset_data.get("ShowDescriptionOnly", False)
        suppress_zero_inches = pset_data.get("SuppressZeroInches", False)
+        suppress_zero_feet = pset_data.get("SuppressZeroFeet", False)
+        is_ordinate = pset_data.get("IsOrdinate", False)
        text_prefix = pset_data.get("TextPrefix", None) or ""
        text_suffix = pset_data.get("TextSuffix", None) or ""
-        custom_unit_list = pset_data.get("CustomUnit", None) or ""
-        custom_unit = custom_unit_list[0] if custom_unit_list else ""
+        custom_units = list(pset_data.get("CustomUnit", None) or [])
+        separator = pset_data.get("Separator", None) or " / "

        return {
            "dimension_style": dimension_style,
            "show_description_only": show_description_only,
            "suppress_zero_inches": suppress_zero_inches,
+            "suppress_zero_feet": suppress_zero_feet,
+            "is_ordinate": is_ordinate,
            "text_prefix": text_prefix,
            "text_suffix": text_suffix,
            "fill_bg": fill_bg,
-            "custom_unit": custom_unit,
+            "custom_units": custom_units,
+            "separator": separator,
        }

    @classmethod
@@ -494,7 +494,7 @@ class BaseDecorator:
        self.draw_label(context, text=text, line_no=line_number_start, multiline=True, **draw_label_kwargs)

    @cache
-    def format_value(self, context, value, suppress_zero_inches=False, custom_unit=None, in_unit_length=False):
+    def format_value(self, context, value, suppress_zero_inches=False, suppress_zero_feet=False, custom_unit=None, in_unit_length=False):
        drawing_pset_data = DrawingsData.data["active_drawing_pset_data"]
        precision = drawing_pset_data.get("MetricPrecision", None)
        if not precision:
@@ -506,6 +506,7 @@ class BaseDecorator:
            precision=precision,
            decimal_places=decimal_places,
            suppress_zero_inches=suppress_zero_inches,
+            suppress_zero_feet=suppress_zero_feet,
            custom_unit=custom_unit,
            in_unit_length=in_unit_length,
        )
@@ -722,11 +723,13 @@ class DimensionDecorator(BaseDecorator):
        if not dimension_data:
            return
        show_description_only = dimension_data["show_description_only"]
+        is_ordinate = dimension_data["is_ordinate"]
        text_prefix = dimension_data["text_prefix"]
        text_suffix = dimension_data["text_suffix"]
        viewportDrawingScale = self.get_viewport_drawing_scale(context)
        text_offset_value = viewportDrawingScale * 3

+        ordinate_total = 0.0
        for i0, i1 in indices:
            v0 = Vector(vertices[i0])
            v1 = Vector(vertices[i1])
@@ -737,6 +740,10 @@ class DimensionDecorator(BaseDecorator):
            text_dir = p1 - p0
            if text_dir.length < 1:
                continue
+            # Normalize so text always reads left-to-right (or bottom-to-top for
+            # vertical dims) regardless of which end was drawn first.
+            if text_dir.x < 0 or (abs(text_dir.x) < 1e-6 and text_dir.y < 0):
+                text_dir = -text_dir
            perpendicular = Vector((-text_dir.y, text_dir.x)).normalized()
            text_offset = perpendicular * text_offset_value

@@ -745,16 +752,25 @@ class DimensionDecorator(BaseDecorator):
                "multiline": True,
                "text_dir": text_dir,
            }
-            base_pos = p0 + text_dir * 0.5
+            base_pos = p1 if is_ordinate else (p0 + p1) / 2

            if not show_description_only:
-                length = (v1 - v0).length
-                text = self.format_value(
-                    context,
-                    length,
-                    suppress_zero_inches=dimension_data["suppress_zero_inches"],
-                    custom_unit=dimension_data["custom_unit"],
-                )
+                segment_length = (v1 - v0).length
+                if is_ordinate:
+                    ordinate_total += segment_length
+                length = ordinate_total if is_ordinate else segment_length
+                units_to_format = dimension_data["custom_units"] if dimension_data["custom_units"] else [None]
+                parts = [
+                    self.format_value(
+                        context,
+                        length,
+                        suppress_zero_inches=dimension_data["suppress_zero_inches"],
+                        suppress_zero_feet=dimension_data["suppress_zero_feet"],
+                        custom_unit=unit,
+                    )
+                    for unit in units_to_format
+                ]
+                text = dimension_data["separator"].join(str(p) for p in parts)
                if isinstance(self, DiameterDecorator):
                    text = "D" + text
                text = text_prefix + text + text_suffix
@@ -765,15 +781,18 @@ class DimensionDecorator(BaseDecorator):

            self.draw_label(
                text=text,
-                pos=base_pos + text_offset,
-                box_alignment="bottom-middle",
+                pos=base_pos + text_offset + (Vector((0, text_offset_value)) if is_ordinate else Vector((0, 0))),
+                box_alignment="bottom-right" if is_ordinate else "bottom-middle",
                multiline_to_bottom=False,
                **common_label_attrs,
            )

            if not show_description_only and description:
                self.draw_label(
-                    text=description, pos=base_pos - text_offset, box_alignment="top-middle", **common_label_attrs
+                    text=description,
+                    pos=base_pos - text_offset + (Vector((0, text_offset_value)) if is_ordinate else Vector((0, 0))),
+                    box_alignment="top-right" if is_ordinate else "top-middle",
+                    **common_label_attrs,
                )


@@ -969,7 +988,9 @@ class RadiusDecorator(BaseDecorator):

        def get_text():
            length = (spline_points[-1] - spline_points[-2]).length
-            return "R" + self.format_value(context, length, custom_unit=dimension_data["custom_unit"])
+            units_to_format = dimension_data["custom_units"] if dimension_data["custom_units"] else [None]
+            parts = [self.format_value(context, length, suppress_zero_feet=dimension_data["suppress_zero_feet"], custom_unit=unit) for unit in units_to_format]
+            return "R" + dimension_data["separator"].join(str(p) for p in parts)

        self.draw_dimension_text(
            context, get_text, description, dimension_data, pos=pos, text_dir=Vector((1, 0)), box_alignment="center"
@@ -1505,6 +1526,20 @@ class ElevationDecorator(BaseDecorator):
            "output_edges": output_edges,
        }

+        # Determine the arrow direction in camera-image-plane (XY) space.
+        # The elevation tag's local -Z is intentionally parallel to the drawing
+        # camera's view direction, so projecting it always gives a near-zero XY
+        # delta.  Fall through to local +X (which is perpendicular to the view
+        # and rotates visibly when the user spins the tag).
+        view_mat = context.region_data.view_matrix
+        edge_dir_2d = Vector((1.0, 0.0))  # final fallback
+        for local_axis in (Vector((0, 0, -1)), Vector((1, 0, 0)), Vector((0, 1, 0))):
+            world_axis = obj.matrix_world.to_3x3() @ local_axis
+            cam_xy = (view_mat.to_3x3() @ world_axis).xy
+            if cam_xy.length > 1e-6:
+                edge_dir_2d = cam_xy.normalized()
+                break
+
        # process edges
        for edge in edges_original:
            v0, v1 = winspace_verts[edge[0]], winspace_verts[edge[1]]
@@ -1513,7 +1548,7 @@ class ElevationDecorator(BaseDecorator):
            circle_head = get_circle_head(circle_size)
            start_i = add_verts_sequence(add_offsets(v0, circle_head), start_i, **out_kwargs, closed=True)

-            edge_dir = (v1 - v0).normalized()
+            edge_dir = edge_dir_2d.to_3d()
            side = (edge_dir.yx * Vector((1, -1))).to_3d()
            triangle_head = get_triangle_head(side, edge_dir, triangle_length, triangle_width)
            start_i = add_verts_sequence(add_offsets(v0, triangle_head), start_i, **out_kwargs, closed=True)
@@ -2129,4 +2164,8 @@ class DecorationsHandler:

        object_decorators = DecoratorData.data.get("object_decorators", [])
        for obj, decorator in object_decorators:
-            decorator.decorate(context, obj)
+            try:
+                decorator.decorate(context, obj)
+            except ReferenceError:
+                DecoratorData.is_loaded = False
+                break
@@ -2297,6 +2297,19 @@ DISC = (
    (1.0, 0.0, 0),
 )

+# Anchor index currently being edited by SetDimensionAnchor (-1 = none).
+_active_anchor_idx: int = -1
+# The annotation curve object being edited (kept so the gizmo group stays
+# visible even when SetDimensionAnchor temporarily changes the active object).
+_editing_annotation_obj = None
+
+
+def set_active_anchor(idx: int, annotation_obj=None) -> None:
+    global _active_anchor_idx, _editing_annotation_obj
+    _active_anchor_idx = idx
+    _editing_annotation_obj = annotation_obj if idx >= 0 else None
+
+
 X3DISC = (
    (0.0, 0.0, 0.0),
    (1.0, 0.0, 0),
@@ -2621,6 +2634,370 @@ class ExtrusionWidget(types.GizmoGroup):
        self.handle.target_set_prop("offset", prop, "value")
        self.guides.target_set_prop("depth", prop, "value")

+
+class GizmoAnchorHandle(bpy.types.Gizmo):
+    """Visual-only dot at a parametric dimension vertex.
+
+    No draw_select/invoke — draw_select puts the gizmo in Blender's select buffer
+    and causes the gizmo system to consume clicks even without an explicit invoke,
+    blocking ClickNearestDimensionAnchor from receiving them.  All click handling
+    is done by the bim.click_nearest_dimension_anchor keymap operator.
+    """
+
+    bl_idname = "BIM_GT_anchor_handle"
+
+    __slots__ = ("anchor_index", "custom_shape")
+
+    def setup(self):
+        self.anchor_index = 0
+        self.custom_shape = self.new_custom_shape(type="TRIS", verts=X3DISC)
+
+    def draw(self, context):
+        self.draw_custom_shape(self.custom_shape)
+
+
+
+class DimensionAnchorWidget(types.GizmoGroup):
+    """Anchor handle gizmos at each vertex of the active parametric dimension.
+
+    Green dots indicate vertices that are anchored to an IFC element face;
+    orange dots are free world-point anchors.  Clicking any dot fires
+    ``bim.set_dimension_anchor`` pre-targeted at that vertex index.
+    """
+
+    bl_idname = "BIM_GGT_dimension_anchors"
+    bl_label = "Dimension Anchor Handles"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT", "SHOW_MODAL_ALL"}
+
+    _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE", "PLAN_LEVEL", "SECTION_LEVEL"))
+    _MAX_ANCHORS = 16
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context) -> bool:
+        if not tool.Ifc.get():
+            return False
+        # Stay visible while SetDimensionAnchor is running (active obj may temporarily
+        # be an IFC element in the face-picking phase rather than the annotation).
+        if _active_anchor_idx >= 0 and _editing_annotation_obj is not None:
+            active = context.active_object
+            if active is _editing_annotation_obj:
+                return True  # annotation still active
+            if active is not None and tool.Ifc.get_entity(active) is not None:
+                return True  # face-picking phase: active obj is a target element
+            # Active object is None or a non-IFC object — the modal ended without
+            # calling set_active_anchor(-1).  Reset stale state and fall through.
+            set_active_anchor(-1)
+        obj = context.active_object
+        if not obj or obj.type != "CURVE":
+            return False
+        if not obj.select_get():
+            return False
+        element = tool.Ifc.get_entity(obj)
+        if not element or not element.is_a("IfcAnnotation"):
+            return False
+        import ifcopenshell.util.element as _ue
+        if _ue.get_predefined_type(element) not in cls._DIM_TYPES:
+            return False
+        pset = _ue.get_pset(element, "BBIM_Dimension")
+        return bool(pset and pset.get("Anchors"))
+
+    def setup(self, context: bpy.types.Context) -> None:
+        self._handles: list = []
+        for _ in range(self._MAX_ANCHORS):
+            gz = self.gizmos.new("BIM_GT_anchor_handle")
+            gz.scale_basis = 0.2
+            gz.use_draw_modal = True
+            gz.hide = True
+            self._handles.append(gz)
+
+    def refresh(self, context: bpy.types.Context) -> None:
+        import json
+        import ifcopenshell.util.element as _ue
+
+        obj = _editing_annotation_obj if _active_anchor_idx >= 0 and _editing_annotation_obj else context.active_object
+        if not obj or not obj.data or not getattr(obj.data, "splines", None):
+            for gz in self._handles:
+                gz.hide = True
+            return
+
+        element = tool.Ifc.get_entity(obj)
+        if not element:
+            for gz in self._handles:
+                gz.hide = True
+            return
+
+        pset = _ue.get_pset(element, "BBIM_Dimension")
+        if not pset or not pset.get("Anchors"):
+            for gz in self._handles:
+                gz.hide = True
+            return
+
+        try:
+            anchors = json.loads(pset["Anchors"])
+        except Exception:
+            for gz in self._handles:
+                gz.hide = True
+            return
+
+        spline = obj.data.splines[0]
+        n = min(len(spline.points), len(anchors), self._MAX_ANCHORS)
+
+        import ifcopenshell.util.element as _ue_gz
+        _ptype_gz = _ue_gz.get_predefined_type(element)
+        _is_elevation_gz = _ptype_gz in ("SECTION_LEVEL", "PLAN_LEVEL")
+
+        for i in range(n):
+            gz = self._handles[i]
+            if _is_elevation_gz:
+                # The object origin IS the anchor reference point (placed at face hit).
+                # Spline vertices are offset from the origin and should not be used.
+                world_co = obj.matrix_world.translation.copy()
+            else:
+                raw_co = spline.points[i].co
+                world_co = obj.matrix_world @ raw_co.to_3d()
+            gz.matrix_basis = Matrix.Translation(world_co)
+            gz.anchor_index = i
+            if i == _active_anchor_idx and obj is _editing_annotation_obj:
+                gz.color = (0.2, 0.7, 1.0)
+                gz.color_highlight = (0.4, 0.85, 1.0)
+            elif anchors[i].get("guid"):
+                gz.color = (0.2, 0.85, 0.2)
+                gz.color_highlight = (0.4, 1.0, 0.4)
+            else:
+                gz.color = (0.9, 0.6, 0.1)
+                gz.color_highlight = (1.0, 0.85, 0.2)
+            gz.alpha = 0.85
+            gz.alpha_highlight = 1.0
+            gz.hide = False
+
+        for i in range(n, self._MAX_ANCHORS):
+            self._handles[i].hide = True
+
+    def draw_prepare(self, context: bpy.types.Context) -> None:
+        self.refresh(context)
+
+
+class DimensionLinePositionWidget(types.GizmoGroup):
+    """Drag handle for the LinePosition of a parametric dimension annotation.
+
+    Shows two opposing cones at the midpoint of the dimension curve, oriented
+    along the horizontal offset axis (cross(world_Z, dim_direction)).  Dragging
+    either cone updates BBIM_Dimension.LinePosition and regenerates the curve in
+    real time.  The forward cone points in +offset_dir; the reverse cone in
+    -offset_dir — both respond to mouse movement along the shared axis so the
+    user can drag in either direction from either handle.
+    """
+
+    bl_idname = "BIM_GGT_dimension_line_position"
+    bl_label = "Dimension Line Position"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT", "SHOW_MODAL_ALL"}
+
+    _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context) -> bool:
+        if not tool.Ifc.get():
+            return False
+        obj = context.active_object
+        if not obj or obj.type != "CURVE":
+            return False
+        element = tool.Ifc.get_entity(obj)
+        if not element or not element.is_a("IfcAnnotation"):
+            return False
+        import ifcopenshell.util.element as _ue
+        if _ue.get_predefined_type(element) not in cls._DIM_TYPES:
+            return False
+        pset = _ue.get_pset(element, "BBIM_Dimension")
+        return bool(pset and pset.get("Anchors"))
+
+    # ------------------------------------------------------------------
+    # Helpers
+
+    @staticmethod
+    def _cam_dir() -> "Vector | None":
+        """Scene camera forward direction, or None."""
+        cam = bpy.context.scene.camera
+        if not cam:
+            return None
+        return (cam.matrix_world.to_3x3() @ Vector((0.0, 0.0, -1.0))).normalized()
+
+    @classmethod
+    def _offset_dir(cls, obj: bpy.types.Object) -> "Vector | None":
+        """World-space direction perpendicular to the dimension line and in the view plane.
+
+        Plan view  (camera mostly vertical): cross(world_Z, dim_dir) — preserves
+        existing stored LinePosition values.
+        Section/elevation (camera mostly horizontal): cross(cam_forward, dim_dir) —
+        keeps the offset axis inside the view plane so the gizmo moves the line
+        visually sideways (up/down in section) rather than into/out of the screen.
+        """
+        if not obj.data or not hasattr(obj.data, "splines") or not obj.data.splines:
+            return None
+        spline = obj.data.splines[0]
+        if len(spline.points) < 2:
+            return None
+        a = obj.matrix_world @ spline.points[0].co.to_3d()
+        b = obj.matrix_world @ spline.points[-1].co.to_3d()
+        dim = b - a
+        if dim.length < 1e-10:
+            return None
+        dim.normalize()
+        cam_view = cls._cam_dir()
+        cam_is_plan = (cam_view is None) or abs(cam_view.z) > 0.7
+        ref = Vector((0.0, 0.0, 1.0)) if cam_is_plan else cam_view
+        od = ref.cross(dim)
+        if od.length < 1e-6:
+            od = Vector((1.0, 0.0, 0.0)).cross(dim)
+        if od.length < 1e-6:
+            return None
+        return od.normalized()
+
+    @staticmethod
+    def _midpoint(obj: bpy.types.Object) -> "Vector":
+        spline = obj.data.splines[0]
+        pts = [obj.matrix_world @ p.co.to_3d() for p in spline.points]
+        return sum(pts, Vector()) / len(pts)
+
+    @staticmethod
+    def _basis(origin: "Vector", x_axis: "Vector") -> "Matrix":
+        """4×4 matrix with translation=origin, local-X=x_axis."""
+        ref = Vector((0.0, 0.0, 1.0)) if abs(x_axis.dot(Vector((0.0, 0.0, 1.0)))) < 0.9 else Vector((1.0, 0.0, 0.0))
+        y_ax = x_axis.cross(ref).normalized()
+        z_ax = x_axis.cross(y_ax)
+        return Matrix([
+            [x_axis.x, y_ax.x, z_ax.x, origin.x],
+            [x_axis.y, y_ax.y, z_ax.y, origin.y],
+            [x_axis.z, y_ax.z, z_ax.z, origin.z],
+            [0.0,      0.0,    0.0,    1.0],
+        ])
+
+    # ------------------------------------------------------------------
+    # Value callbacks
+
+    def _get_pos(self) -> float:
+        obj = bpy.context.active_object
+        if not obj:
+            return 0.0
+        element = tool.Ifc.get_entity(obj)
+        if not element:
+            return 0.0
+        import ifcopenshell.util.element as _ue
+        pset = _ue.get_pset(element, "BBIM_Dimension")
+        if not pset:
+            return 0.0
+        stored = pset.get("LinePosition")
+        if stored is not None:
+            return float(stored)
+        # Natural position: projection of midpoint onto offset axis
+        od = self._offset_dir(obj)
+        if od is None:
+            return 0.0
+        return self._midpoint(obj).dot(od)
+
+    def _set_pos(self, value: float) -> None:
+        bpy.ops.ed.undo_push(message="Set Line Position")
+        import json
+        import numpy as np
+        import ifcopenshell.util.element as _ue
+        import ifcopenshell.api.pset as _pset_api
+        import ifcopenshell.api.drawing as drawing_api
+        from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+        obj = bpy.context.active_object
+        if not obj:
+            return
+        file = tool.Ifc.get()
+        if not file:
+            return
+        element = tool.Ifc.get_entity(obj)
+        if not element:
+            return
+        pset_data = _ue.get_pset(element, "BBIM_Dimension")
+        if not pset_data:
+            return
+
+        pset_entity = file.by_id(pset_data["id"])
+        _pset_api.edit_pset(file, pset=pset_entity, properties={"LinePosition": value})
+
+        anchors = json.loads(pset_data.get("Anchors") or "[]")
+        placement_override: dict = {}
+        for a in anchors:
+            guid = a.get("guid")
+            if not guid:
+                continue
+            try:
+                elem = file.by_guid(guid)
+                elem_obj = tool.Ifc.get_object(elem)
+                if elem_obj:
+                    placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+            except Exception:
+                pass
+
+        cam_view = self._cam_dir()
+        cam_dir_tuple = tuple(cam_view) if cam_view is not None else None
+        resolved_pts = drawing_api.regenerate_dimension(
+            file, element, placement_override=placement_override, camera_dir=cam_dir_tuple
+        )
+        if resolved_pts:
+            _update_blender_curve(element, resolved_pts)
+        tool.Blender.update_viewport()
+
+    # ------------------------------------------------------------------
+    # GizmoGroup interface
+
+    def _make_cone(self, color: tuple, highlight: tuple) -> "bpy.types.Gizmo":
+        gz = self.gizmos.new("BIM_GT_gizmo_cone")
+        gz.color = color
+        gz.alpha = 0.8
+        gz.color_highlight = highlight
+        gz.alpha_highlight = 1.0
+        gz.scale_basis = 0.15
+        gz.use_draw_modal = True
+        gz.prop_name = "Line Position"
+        gz.move_get_cb = self._get_pos
+        gz.move_set_cb = self._set_pos
+        gz.gizmo_group = self
+        gz.delta_scale = 1.0
+        return gz
+
+    def setup(self, context: bpy.types.Context) -> None:
+        color = (0.9, 0.6, 0.1)
+        highlight = (1.0, 0.9, 0.2)
+        self.gz_fwd = self._make_cone(color, highlight)
+        self.gz_rev = self._make_cone(color, highlight)
+
+    def refresh(self, context: bpy.types.Context) -> None:
+        obj = context.active_object
+        if not obj:
+            self.gz_fwd.hide = self.gz_rev.hide = True
+            return
+
+        od = self._offset_dir(obj)
+        if od is None:
+            self.gz_fwd.hide = self.gz_rev.hide = True
+            return
+
+        mid = self._midpoint(obj)
+        # Lift each cone off the dimension line so the arrow base doesn't
+        # overlap anchor dots.  0.3 m gives clear separation at typical zoom.
+        _GAP = 0.15
+        fwd_origin = mid + _GAP * od
+        rev_origin = mid - _GAP * od
+
+        self.gz_fwd.matrix_basis = self._basis(fwd_origin, od)
+        self.gz_fwd.axis = od.copy()
+        self.gz_fwd.hide = False
+
+        # Reverse cone: visually points in -od; same drag axis so both cones
+        # respond identically — drag toward either tip to move the line.
+        self.gz_rev.matrix_basis = self._basis(rev_origin, -od)
+        self.gz_rev.axis = od.copy()
+        self.gz_rev.hide = False
+
    @staticmethod
    def get_scale_value(system: str, length_unit: str) -> float:
        scale_value = 1
@@ -2645,6 +3022,76 @@ class ExtrusionWidget(types.GizmoGroup):
        return scale_value


+class DimensionDriveLabelWidget(types.GizmoGroup):
+    """Pen-icon gizmos at each segment midpoint of the active parametric dimension.
+
+    Clicking a pen invokes ``bim.drive_dimension_length`` for that segment,
+    opening a dialog pre-filled with the current length.
+    """
+
+    bl_idname = "BIM_GGT_dimension_drive_label"
+    bl_label = "Dimension Drive Label"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT", "SHOW_MODAL_ALL"}
+
+    _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+    _MAX_SEGMENTS = 15
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context) -> bool:
+        if not tool.Ifc.get():
+            return False
+        obj = context.active_object
+        if not obj or obj.type != "CURVE":
+            return False
+        element = tool.Ifc.get_entity(obj)
+        if not element or not element.is_a("IfcAnnotation"):
+            return False
+        import ifcopenshell.util.element as _ue
+        if _ue.get_predefined_type(element) not in cls._DIM_TYPES:
+            return False
+        pset = _ue.get_pset(element, "BBIM_Dimension")
+        return bool(pset and pset.get("Anchors"))
+
+    def setup(self, context: bpy.types.Context) -> None:
+        self._labels: list = []
+        for _ in range(self._MAX_SEGMENTS):
+            gz = self.gizmos.new("BIM_GT_drive_dim_label")
+            gz.color = (0.9, 0.75, 0.1)
+            gz.color_highlight = (1.0, 0.95, 0.3)
+            gz.alpha = 0.85
+            gz.alpha_highlight = 1.0
+            gz.scale_basis = 0.18
+            gz.use_draw_modal = True
+            gz.hide = True
+            self._labels.append(gz)
+
+    def refresh(self, context: bpy.types.Context) -> None:
+        obj = context.active_object
+        if not obj or not obj.data or not getattr(obj.data, "splines", None) or not obj.data.splines:
+            for gz in self._labels:
+                gz.hide = True
+            return
+
+        spline = obj.data.splines[0]
+        pts = [obj.matrix_world @ p.co.to_3d() for p in spline.points]
+        n_segs = min(len(pts) - 1, self._MAX_SEGMENTS)
+
+        for i in range(n_segs):
+            gz = self._labels[i]
+            mid = (pts[i] + pts[i + 1]) * 0.5
+            gz.matrix_basis = Matrix.Translation(mid)
+            gz.segment_index = i
+            gz.hide = False
+
+        for i in range(n_segs, self._MAX_SEGMENTS):
+            self._labels[i].hide = True
+
+    def draw_prepare(self, context: bpy.types.Context) -> None:
+        self.refresh(context)
+
+
 # ============================================================================
 # Core Gizmo Classes
 # ============================================================================
@@ -3611,6 +4058,24 @@ class GizmoPen(StaticTrisGizmoMixin, bpy.types.Gizmo):
    )


+class GizmoDriveDimLabel(bpy.types.Gizmo):
+    """Visual-only pen icon at a parametric dimension segment midpoint.
+
+    No draw_select/invoke — click handling is done by ClickNearestDimensionAnchor,
+    which dispatches bim.drive_dimension_length on a plain LMB at a midpoint.
+    """
+
+    bl_idname = "BIM_GT_drive_dim_label"
+    __slots__ = ("segment_index", "custom_shape")
+
+    def setup(self):
+        self.segment_index = 0
+        self.custom_shape = self.new_custom_shape("TRIS", GizmoPen.tris)
+
+    def draw(self, context):
+        self.draw_custom_shape(self.custom_shape)
+
+
 class GizmoValidate(StaticTrisGizmoMixin, bpy.types.Gizmo):
    """Validate/checkmark icon gizmo for confirming edits."""

@@ -16,15 +16,148 @@
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

+import json
+
 import bpy
+import numpy as np
 from bpy.app.handlers import persistent

 import bonsai.bim.module.drawing.decoration as decoration
 import bonsai.tool as tool

+# ---------------------------------------------------------------------------
+# Parametric dimension auto-regeneration state
+# ---------------------------------------------------------------------------
+
+# Maps element GUID → list of annotation STEP IDs that reference it.
+_dim_guid_index: dict = {}
+# Persistent tessellation cache for the depsgraph handler (element id → shape).
+_dim_shape_cache: dict = {}
+# Set True whenever BBIM_Dimension anchors change or a new file loads.
+_dim_index_dirty: bool = True
+# Re-entry guard so curve updates don't trigger a second handler call.
+_dim_handler_running: bool = False
+
+
+def invalidate_dim_index() -> None:
+    """Mark the GUID index as stale so it is rebuilt on the next handler call."""
+    global _dim_index_dirty, _dim_shape_cache
+    _dim_index_dirty = True
+    _dim_shape_cache.clear()
+
+
+def _rebuild_dim_guid_index(file) -> None:
+    global _dim_guid_index, _dim_index_dirty
+    import ifcopenshell.util.element
+
+    _dim_guid_index = {}
+    for annotation in file.by_type("IfcAnnotation"):
+        pset_data = ifcopenshell.util.element.get_pset(annotation, "BBIM_Dimension")
+        if not pset_data or not pset_data.get("Anchors"):
+            continue
+        try:
+            anchors = json.loads(pset_data["Anchors"])
+        except Exception:
+            continue
+        ann_id = annotation.id()
+        for anchor in anchors:
+            guid = anchor.get("guid")
+            if not guid:
+                continue
+            ids = _dim_guid_index.setdefault(guid, [])
+            if ann_id not in ids:
+                ids.append(ann_id)
+    _dim_index_dirty = False
+
+
+def regenerate_dims_for_layer(file, layer) -> None:
+    """Regenerate all parametric dimensions anchored to elements that use *layer*."""
+    global _dim_shape_cache, _dim_index_dirty, _dim_guid_index
+
+    if _dim_index_dirty:
+        _rebuild_dim_guid_index(file)
+
+    affected_guids: set = set()
+    for layer_set in file.get_inverse(layer):
+        if not layer_set.is_a("IfcMaterialLayerSet"):
+            continue
+        for inv in file.get_inverse(layer_set):
+            if inv.is_a("IfcRelAssociatesMaterial"):
+                rels = [inv]
+            elif inv.is_a("IfcMaterialLayerSetUsage"):
+                rels = [r for r in file.get_inverse(inv) if r.is_a("IfcRelAssociatesMaterial")]
+            else:
+                continue
+            for rel in rels:
+                for element in rel.RelatedObjects:
+                    if hasattr(element, "GlobalId"):
+                        affected_guids.add(element.GlobalId)
+                        _dim_shape_cache.pop(element.id(), None)
+
+    if not affected_guids:
+        return
+
+    annotation_ids: set = set()
+    for guid in affected_guids:
+        for ann_id in _dim_guid_index.get(guid, []):
+            annotation_ids.add(ann_id)
+
+    if not annotation_ids:
+        return
+
+    import ifcopenshell.util.element
+    import ifcopenshell.api.drawing as drawing_api
+    import ifcopenshell.geom
+    from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+    geom_settings = ifcopenshell.geom.settings()
+    geom_settings.set("APPLY_DEFAULT_MATERIALS", False)
+
+    cam = bpy.context.scene.camera
+    cam_dir_tuple = None
+    if cam:
+        from mathutils import Vector as _Vec
+        cam_dir_tuple = tuple((cam.matrix_world.to_3x3() @ _Vec((0, 0, -1))).normalized())
+
+    for ann_id in annotation_ids:
+        try:
+            annotation = file.by_id(ann_id)
+        except Exception:
+            continue
+        pset = ifcopenshell.util.element.get_pset(annotation, "BBIM_Dimension")
+        if not pset:
+            continue
+        placement_override: dict = {}
+        try:
+            anchors_raw = json.loads(pset.get("Anchors") or "[]")
+            for anchor in anchors_raw:
+                guid = anchor.get("guid")
+                if not guid:
+                    continue
+                try:
+                    elem = file.by_guid(guid)
+                    elem_obj = tool.Ifc.get_object(elem)
+                    if elem_obj:
+                        placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+                except Exception:
+                    pass
+        except Exception:
+            pass
+        resolved_pts = drawing_api.regenerate_dimension(
+            file,
+            annotation,
+            settings=geom_settings,
+            shape_cache=_dim_shape_cache,
+            placement_override=placement_override,
+            camera_dir=cam_dir_tuple,
+        )
+        if resolved_pts:
+            _update_blender_curve(annotation, resolved_pts)
+

@persistent
 def load_post(*args):
+    invalidate_dim_index()
    props = tool.Drawing.get_document_props()
    if props.should_draw_decorations:
        decoration.DecorationsHandler.install(bpy.context)
@@ -61,3 +194,193 @@ def set_active_camera_resolution(scene: bpy.types.Scene) -> None:
        raster_x, raster_y = props.update_camera_resolution()
        scene_render.resolution_x = raster_x
        scene_render.resolution_y = raster_y
+
+
+def _sync_dimension_anchors_to_curve(file, annotation, obj) -> bool:
+    """Sync BBIM_Dimension.Anchors length to match the curve's spline point count.
+
+    Called when the user adds or removes vertices from a dimension annotation in
+    Edit Mode.  New vertices get a free WORLD-type anchor at their current world
+    position; removed tail vertices simply lose their anchor entries.
+
+    Returns True if the pset was changed.
+    """
+    import ifcopenshell.util.element
+    import ifcopenshell.api.pset
+
+    if not obj.data or not getattr(obj.data, "splines", None) or not obj.data.splines:
+        return False
+
+    pset_data = ifcopenshell.util.element.get_pset(annotation, "BBIM_Dimension")
+    if not pset_data or not pset_data.get("Anchors"):
+        return False
+
+    try:
+        anchors: list = json.loads(pset_data["Anchors"])
+    except Exception:
+        return False
+
+    spline = obj.data.splines[0]
+    spline_world = [obj.matrix_world @ p.co.to_3d() for p in spline.points]
+    n_pts = len(spline_world)
+    n_anchors = len(anchors)
+
+    if n_pts == n_anchors:
+        return False
+
+    # Match each spline point to the nearest unused anchor by proximity.
+    # This handles insertions (subdivide) and deletions correctly regardless
+    # of where in the polyline the edit happened.
+    _MATCH_THRESH_SQ = 1e-4  # 1 cm² — distinguishes existing pts from new midpoints
+    used: set = set()
+    new_anchors: list = []
+
+    for pt in spline_world:
+        best_idx, best_sq = None, float("inf")
+        for i, anc in enumerate(anchors):
+            if i in used:
+                continue
+            stored = anc.get("pt")
+            if not stored:
+                continue
+            dx, dy, dz = stored[0] - pt.x, stored[1] - pt.y, stored[2] - pt.z
+            sq = dx * dx + dy * dy + dz * dz
+            if sq < best_sq:
+                best_sq, best_idx = sq, i
+        if best_idx is not None and best_sq < _MATCH_THRESH_SQ:
+            new_anchors.append(anchors[best_idx])
+            used.add(best_idx)
+        else:
+            new_anchors.append({
+                "guid": None,
+                "type": "WORLD",
+                "addr": {},
+                "hint": None,
+                "pt": [pt.x, pt.y, pt.z],
+            })
+
+
+    pset_entity = file.by_id(pset_data["id"])
+    ifcopenshell.api.pset.edit_pset(file, pset=pset_entity, properties={"Anchors": json.dumps(new_anchors)})
+    invalidate_dim_index()
+    return True
+
+
+@persistent
+def depsgraph_update_post_handler(scene, depsgraph):
+    """Auto-regenerate parametric dimensions when referenced elements are moved."""
+    global _dim_handler_running, _dim_index_dirty, _dim_guid_index, _dim_shape_cache
+
+    if _dim_handler_running:
+        return
+
+    file = tool.Ifc.get()
+    if not file:
+        return
+
+    if _dim_index_dirty:
+        _rebuild_dim_guid_index(file)
+
+    import ifcopenshell.util.element
+
+    moved_guids: set = set()
+    edited_annotation_ids: set = set()
+
+    for update in depsgraph.updates:
+        obj = update.id
+        if not isinstance(obj, bpy.types.Object):
+            continue
+        if not (update.is_updated_transform or update.is_updated_geometry):
+            continue
+        element = tool.Ifc.get_entity(obj)
+        if element is None or not hasattr(element, "GlobalId"):
+            continue
+
+
+        if update.is_updated_geometry and obj.type == "CURVE" and element.is_a("IfcAnnotation"):
+            import ifcopenshell.util.element as _ue
+            ptype = _ue.get_predefined_type(element)
+            if ptype in ("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"):
+                changed = _sync_dimension_anchors_to_curve(file, element, obj)
+                if changed:
+                    edited_annotation_ids.add(element.id())
+                continue
+
+        moved_guids.add(element.GlobalId)
+        if update.is_updated_geometry:
+            _dim_shape_cache.pop(element.id(), None)
+
+    annotation_ids: set = set(edited_annotation_ids)
+    for guid in moved_guids:
+        for ann_id in _dim_guid_index.get(guid, []):
+            annotation_ids.add(ann_id)
+
+    if not annotation_ids:
+        return
+
+    import ifcopenshell.api.drawing as drawing_api
+    import ifcopenshell.geom
+    from bonsai.bim.module.drawing.operator import _update_blender_curve, _update_elevation_marker_z
+
+    geom_settings = ifcopenshell.geom.settings()
+    geom_settings.set("APPLY_DEFAULT_MATERIALS", False)
+
+    cam = bpy.context.scene.camera
+    cam_dir_tuple = None
+    if cam:
+        from mathutils import Vector as _Vec
+        cam_dir_tuple = tuple((cam.matrix_world.to_3x3() @ _Vec((0, 0, -1))).normalized())
+
+    _dim_handler_running = True
+    try:
+        for ann_id in annotation_ids:
+            try:
+                annotation = file.by_id(ann_id)
+            except Exception:
+                continue
+
+            pset = ifcopenshell.util.element.get_pset(annotation, "BBIM_Dimension")
+            if not pset:
+                continue
+
+            placement_override: dict = {}
+            try:
+                anchors_raw = json.loads(pset.get("Anchors") or "[]")
+                for anchor in anchors_raw:
+                    guid = anchor.get("guid")
+                    if not guid:
+                        continue
+                    try:
+                        elem = file.by_guid(guid)
+                        elem_id = elem.id()
+                        if elem_id in placement_override:
+                            continue
+                        elem_obj = tool.Ifc.get_object(elem)
+                        if elem_obj:
+                            placement_override[elem_id] = np.array(elem_obj.matrix_world)
+                    except Exception:
+                        pass
+            except Exception:
+                pass
+
+            ptype = ifcopenshell.util.element.get_predefined_type(annotation)
+            if ptype in ("SECTION_LEVEL", "PLAN_LEVEL"):
+                _update_elevation_marker_z(
+                    file, annotation,
+                    settings=geom_settings,
+                    shape_cache=_dim_shape_cache,
+                    placement_override=placement_override,
+                )
+            else:
+                resolved_pts = drawing_api.regenerate_dimension(
+                    file,
+                    annotation,
+                    settings=geom_settings,
+                    shape_cache=_dim_shape_cache,
+                    placement_override=placement_override,
+                    camera_dir=cam_dir_tuple,
+                )
+                if resolved_pts:
+                    _update_blender_curve(annotation, resolved_pts)
+    finally:
+        _dim_handler_running = False
@@ -170,6 +170,7 @@ def format_distance(
    precision=None,
    decimal_places=None,
    suppress_zero_inches=False,
+    suppress_zero_feet=False,
    in_unit_length=False,
    custom_unit=None,
 ):
@@ -319,10 +320,10 @@ def format_distance(
            tx_dist = ""
            if feet:
                tx_dist += str(feet) + "'"
-            if not feet and not add_inches:
+            if not feet and not add_inches and not suppress_zero_feet:
                tx_dist += str(feet) + "'"

-            if not feet and add_inches and unit_length != "INCHES":
+            if not feet and add_inches and unit_length != "INCHES" and not suppress_zero_feet:
                if value < 0:
                    tx_dist += "-0' - "
                else:
@@ -95,6 +95,14 @@ def update_diagram_scale(self: "BIMCameraProperties", context: bpy.types.Context
    ifcopenshell.api.pset.edit_pset(tool.Ifc.get(), pset=pset, properties=diagram_scale)
    self.update_camera_resolution()

+    group = tool.Drawing.get_drawing_group(element)
+    if group:
+        for annotation in tool.Drawing.get_group_elements(group) or []:
+            if annotation.is_a("IfcAnnotation") and ifcopenshell.util.element.get_predefined_type(annotation) == "SECTION":
+                ann_obj = tool.Ifc.get_object(annotation)
+                if ann_obj:
+                    tool.Drawing.update_section_endpoints(ann_obj, camera)
+

 def update_is_nts(self: "BIMCameraProperties", context: bpy.types.Context) -> None:
    if not self.update_props:
@@ -1038,6 +1046,276 @@ def update_sheet_data(self, context):
    SheetsData.is_loaded = False


+# Guard against re-entrant calls when one constraint callback clears the other property.
+_face_constraint_updating = False
+
+
+def _update_force_perpendicular(self, context):
+    """Apply ForcePerpendicularToFace to all selected dimension annotations and regenerate them."""
+    global _face_constraint_updating
+    if _face_constraint_updating:
+        return
+    _face_constraint_updating = True
+    try:
+        import json
+        import numpy as np
+        import ifcopenshell.util.element
+        import ifcopenshell.api.pset
+        import ifcopenshell.api.drawing as drawing_api
+        import bonsai.tool as tool
+
+        file = tool.Ifc.get()
+        if not file:
+            return
+
+        new_value = self.force_perpendicular_to_face
+        if new_value and self.force_parallel_to_face:
+            self.force_parallel_to_face = False
+        _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+
+        targets = []
+        for obj in context.selected_objects:
+            element = tool.Ifc.get_entity(obj)
+            if not element or not element.is_a("IfcAnnotation"):
+                continue
+            if ifcopenshell.util.element.get_predefined_type(element) not in _DIM_TYPES:
+                continue
+            pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension")
+            if not pset_data:
+                continue
+            targets.append((obj, element, pset_data))
+
+        if not targets:
+            return
+
+        from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+        for obj, element, pset_data in targets:
+            pset_entity = file.by_id(pset_data["id"])
+            pset_props = {"ForcePerpendicularToFace": new_value}
+            if new_value:
+                pset_props["ForceParallelToFace"] = False
+            ifcopenshell.api.pset.edit_pset(file, pset=pset_entity, properties=pset_props)
+
+            anchors = json.loads(pset_data.get("Anchors") or "[]")
+            placement_override = {}
+            for a in anchors:
+                guid = a.get("guid")
+                if not guid:
+                    continue
+                try:
+                    elem = file.by_guid(guid)
+                    elem_obj = tool.Ifc.get_object(elem)
+                    if elem_obj:
+                        placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+                except Exception:
+                    pass
+
+            resolved_pts = drawing_api.regenerate_dimension(file, element, placement_override=placement_override)
+            if resolved_pts:
+                _update_blender_curve(element, resolved_pts)
+    finally:
+        _face_constraint_updating = False
+
+
+def _update_force_parallel(self, context):
+    """Apply ForceParallelToFace to all selected dimension annotations and regenerate them."""
+    global _face_constraint_updating
+    if _face_constraint_updating:
+        return
+    _face_constraint_updating = True
+    try:
+        import json
+        import numpy as np
+        import ifcopenshell.util.element
+        import ifcopenshell.api.pset
+        import ifcopenshell.api.drawing as drawing_api
+        import bonsai.tool as tool
+        from mathutils import Vector
+
+        file = tool.Ifc.get()
+        if not file:
+            return
+
+        new_value = self.force_parallel_to_face
+        if new_value and self.force_perpendicular_to_face:
+            self.force_perpendicular_to_face = False
+        _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+
+        targets = []
+        for obj in context.selected_objects:
+            element = tool.Ifc.get_entity(obj)
+            if not element or not element.is_a("IfcAnnotation"):
+                continue
+            if ifcopenshell.util.element.get_predefined_type(element) not in _DIM_TYPES:
+                continue
+            pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension")
+            if not pset_data:
+                continue
+            targets.append((obj, element, pset_data))
+
+        if not targets:
+            return
+
+        cam = context.scene.camera
+        cam_dir_tuple = None
+        if cam:
+            cd = cam.matrix_world.to_3x3() @ Vector((0, 0, -1))
+            cd.normalize()
+            cam_dir_tuple = (cd.x, cd.y, cd.z)
+
+        from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+        for obj, element, pset_data in targets:
+            pset_entity = file.by_id(pset_data["id"])
+            pset_props = {"ForceParallelToFace": new_value}
+            if new_value:
+                pset_props["ForcePerpendicularToFace"] = False
+            ifcopenshell.api.pset.edit_pset(file, pset=pset_entity, properties=pset_props)
+
+            anchors = json.loads(pset_data.get("Anchors") or "[]")
+            placement_override = {}
+            for a in anchors:
+                guid = a.get("guid")
+                if not guid:
+                    continue
+                try:
+                    elem = file.by_guid(guid)
+                    elem_obj = tool.Ifc.get_object(elem)
+                    if elem_obj:
+                        placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+                except Exception:
+                    pass
+
+            resolved_pts = drawing_api.regenerate_dimension(
+                file, element, placement_override=placement_override, camera_dir=cam_dir_tuple
+            )
+            if resolved_pts:
+                _update_blender_curve(element, resolved_pts)
+    finally:
+        _face_constraint_updating = False
+
+
+def _get_line_position(self) -> float:
+    """Return LinePosition from the active annotation's BBIM_Dimension pset.
+
+    Falls back to the natural anchor projection when LinePosition has not been
+    explicitly set, so the field always shows a meaningful value.
+    """
+    import math
+    import json
+    try:
+        import bpy as _bpy
+        import ifcopenshell.util.element as _ue
+        import bonsai.tool as _tool
+        obj = getattr(_bpy.context, "active_object", None)
+        if obj:
+            element = _tool.Ifc.get_entity(obj)
+            if element and element.is_a("IfcAnnotation"):
+                pset = _ue.get_pset(element, "BBIM_Dimension")
+                if pset:
+                    stored = pset.get("LinePosition")
+                    if stored is not None:
+                        return float(stored)
+                    raw = pset.get("Anchors")
+                    if raw:
+                        anchors = json.loads(raw)
+                        if len(anchors) >= 2 and anchors[0].get("pt") and anchors[1].get("pt"):
+                            a, b = anchors[0]["pt"], anchors[1]["pt"]
+                            dx, dy, dz = b[0] - a[0], b[1] - a[1], b[2] - a[2]
+                            m = math.sqrt(dx * dx + dy * dy + dz * dz)
+                            if m > 1e-10:
+                                ddx, ddy, ddz = dx / m, dy / m, dz / m
+                                cam = _bpy.context.scene.camera
+                                cam_is_plan = True
+                                cvx, cvy, cvz = 0.0, 0.0, 1.0
+                                if cam:
+                                    from mathutils import Vector as _Vec
+                                    cv = (cam.matrix_world.to_3x3() @ _Vec((0, 0, -1))).normalized()
+                                    cvx, cvy, cvz = cv.x, cv.y, cv.z
+                                    cam_is_plan = abs(cvz) > 0.7
+                                if cam_is_plan:
+                                    # cross(world_Z, dim_dir)
+                                    ox, oy, oz = -ddy, ddx, 0.0
+                                else:
+                                    # cross(cam_dir, dim_dir)
+                                    ox = cvy * ddz - cvz * ddy
+                                    oy = cvz * ddx - cvx * ddz
+                                    oz = cvx * ddy - cvy * ddx
+                                om = math.sqrt(ox * ox + oy * oy + oz * oz)
+                                if om > 1e-6:
+                                    od = (ox / om, oy / om, oz / om)
+                                    pt = anchors[0]["pt"]
+                                    return float(pt[0] * od[0] + pt[1] * od[1] + pt[2] * od[2])
+    except Exception:
+        pass
+    return 0.0
+
+
+def _set_line_position(self, value: float) -> None:
+    """Write LinePosition to all selected dimension annotations and regenerate."""
+    import json
+    import numpy as np
+    import ifcopenshell.util.element
+    import ifcopenshell.api.pset
+    import ifcopenshell.api.drawing as drawing_api
+    import bonsai.tool as tool
+
+    file = tool.Ifc.get()
+    if not file:
+        return
+
+    _DIM_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+
+    targets = []
+    import bpy as _bpy
+    for obj in getattr(_bpy.context, "selected_objects", []):
+        element = tool.Ifc.get_entity(obj)
+        if not element or not element.is_a("IfcAnnotation"):
+            continue
+        if ifcopenshell.util.element.get_predefined_type(element) not in _DIM_TYPES:
+            continue
+        pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension")
+        if not pset_data:
+            continue
+        targets.append((obj, element, pset_data))
+
+    if not targets:
+        return
+
+    from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+    cam = _bpy.context.scene.camera
+    cam_dir_tuple = None
+    if cam:
+        from mathutils import Vector as _Vec
+        cam_dir_tuple = tuple((cam.matrix_world.to_3x3() @ _Vec((0, 0, -1))).normalized())
+
+    for obj, element, pset_data in targets:
+        pset_entity = file.by_id(pset_data["id"])
+        ifcopenshell.api.pset.edit_pset(file, pset=pset_entity, properties={"LinePosition": value})
+
+        anchors = json.loads(pset_data.get("Anchors") or "[]")
+        placement_override = {}
+        for a in anchors:
+            guid = a.get("guid")
+            if not guid:
+                continue
+            try:
+                elem = file.by_guid(guid)
+                elem_obj = tool.Ifc.get_object(elem)
+                if elem_obj:
+                    placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+            except Exception:
+                pass
+
+        resolved_pts = drawing_api.regenerate_dimension(
+            file, element, placement_override=placement_override, camera_dir=cam_dir_tuple
+        )
+        if resolved_pts:
+            _update_blender_curve(element, resolved_pts)
+
+
 class BIMAnnotationProperties(PropertyGroup):
    object_type: bpy.props.EnumProperty(
        name="Annotation Object Type", items=annotation_classes, default="TEXT", update=update_annotation_object_type
@@ -1051,6 +1329,25 @@ class BIMAnnotationProperties(PropertyGroup):
    )
    is_adding_type: bpy.props.BoolProperty(default=False)
    type_name: bpy.props.StringProperty(name="Name", default="TYPEX")
+    force_perpendicular_to_face: bpy.props.BoolProperty(
+        name="Force ⊥ to Face",
+        description="Constrain dimension vertices to the face normal of the first anchor. When dimensions are selected, toggling this updates them all.",
+        default=False,
+        update=_update_force_perpendicular,
+    )
+    force_parallel_to_face: bpy.props.BoolProperty(
+        name="Force ∥ to Face",
+        description="Constrain dimension vertices to run parallel to the face of the first anchor (along the face, perpendicular to its normal). When dimensions are selected, toggling this updates them all.",
+        default=False,
+        update=_update_force_parallel,
+    )
+    line_position: bpy.props.FloatProperty(
+        name="Line Position",
+        description="Absolute world position of the dimension line along the horizontal axis perpendicular to the dimension. The line is held at this fixed global coordinate even when the measured geometry moves. Updates all selected dimensions.",
+        unit="LENGTH",
+        get=_get_line_position,
+        set=_set_line_position,
+    )
    tag_rotation_mode: bpy.props.EnumProperty(
        name="Tag Rotation Mode",
        description="How to orient the tag relative to the tagged object",
@@ -872,7 +872,11 @@ class SvgWriter:

        v1 = self.project_point_onto_camera(obj.matrix_world @ Vector((0, 0, 0)))
        v2 = self.project_point_onto_camera(obj.matrix_world @ Vector((0, 0, -1)))
-        angle = -math.degrees((v2 - v1).xy.angle_signed(Vector((0, 1))))
+        delta = (v2 - v1).xy
+        if delta.length <= 1e-6:
+            v2 = self.project_point_onto_camera(obj.matrix_world @ Vector((1, 0, 0)))
+            delta = (v2 - v1).xy
+        angle = -math.degrees(delta.angle_signed(Vector((0, 1)))) if delta.length > 1e-6 else 90.0

        transform = "rotate({}, {}, {})".format(angle, *symbol_position_svg.xy)

@@ -895,6 +899,8 @@ class SvgWriter:
        reference_id = "-"
        sheet_id = "-"
        drawing = tool.Drawing.get_annotation_element(element)
+        if not drawing:
+            return ("-", "-")
        reference = tool.Drawing.get_drawing_reference(drawing)
        if reference:
            for sheet_reference in tool.Ifc.get().by_type("IfcDocumentReference"):
@@ -1367,14 +1373,18 @@ class SvgWriter:

            def get_text():
                radius = (points[-1].co - points[-2].co).length
-                radius = helper.format_distance(
-                    radius,
-                    precision=self.precision,
-                    decimal_places=self.decimal_places,
-                    custom_unit=dimension_data["custom_unit"],
-                )
-                text = f"R{radius}"
-                return text
+                units_to_format = dimension_data["custom_units"] if dimension_data["custom_units"] else [None]
+                parts = [
+                    helper.format_distance(
+                        radius,
+                        precision=self.precision,
+                        decimal_places=self.decimal_places,
+                        suppress_zero_feet=dimension_data["suppress_zero_feet"],
+                        custom_unit=unit,
+                    )
+                    for unit in units_to_format
+                ]
+                return "R" + dimension_data["separator"].join(str(p) for p in parts)

            self.draw_dimension_text(
                get_text, tag, dimension_data, text_position=text_position, class_str="RADIUS", box_alignment="center"
@@ -1501,10 +1511,12 @@ class SvgWriter:
                    text_format=lambda x: "D" + x,
                    show_description_only=dimension_data["show_description_only"],
                    suppress_zero_inches=dimension_data["suppress_zero_inches"],
+                    suppress_zero_feet=dimension_data["suppress_zero_feet"],
                    text_prefix=dimension_data["text_prefix"],
                    text_suffix=dimension_data["text_suffix"],
                    fill_bg=dimension_data["fill_bg"],
-                    custom_unit=dimension_data["custom_unit"],
+                    custom_units=dimension_data["custom_units"],
+                    separator=dimension_data["separator"],
                )

    def draw_dimension_annotations(self, obj: bpy.types.Object) -> None:
@@ -1515,11 +1527,15 @@ class SvgWriter:
        dimension_data = DecoratorData.get_dimension_data(obj)

        assert isinstance(obj.data, bpy.types.Curve)
+        is_ordinate = dimension_data["is_ordinate"]
        for spline in obj.data.splines:
            points = self.get_spline_points(spline)
+            ordinate_total = 0.0
            for i in range(len(points) - 1):
                v0_global = matrix_world @ points[i].co.xyz
                v1_global = matrix_world @ points[i + 1].co.xyz
+                if is_ordinate:
+                    ordinate_total += (v1_global - v0_global).length
                self.draw_dimension_annotation(
                    v0_global,
                    v1_global,
@@ -1527,10 +1543,13 @@ class SvgWriter:
                    dimension_text=dimension_text,
                    show_description_only=dimension_data["show_description_only"],
                    suppress_zero_inches=dimension_data["suppress_zero_inches"],
+                    suppress_zero_feet=dimension_data["suppress_zero_feet"],
                    text_prefix=dimension_data["text_prefix"],
                    text_suffix=dimension_data["text_suffix"],
                    fill_bg=dimension_data["fill_bg"],
-                    custom_unit=dimension_data["custom_unit"],
+                    custom_units=dimension_data["custom_units"],
+                    separator=dimension_data["separator"],
+                    distance_override=ordinate_total if is_ordinate else None,
                )

    def draw_measureit_arch_dimension_annotations(self) -> None:
@@ -1554,10 +1573,13 @@ class SvgWriter:
        text_format=lambda x: x,
        show_description_only=False,
        suppress_zero_inches=False,
+        suppress_zero_feet=False,
        text_prefix="",
        text_suffix="",
        fill_bg=False,
-        custom_unit=None,
+        custom_units=None,
+        separator=" / ",
+        distance_override=None,
    ) -> None:
        offset = Vector([self.raw_width, self.raw_height]) / 2
        v0 = self.project_point_onto_camera(v0_global)
@@ -1566,12 +1588,24 @@ class SvgWriter:
        end = (offset + v1.xy * Vector((1, -1))) * self.svg_scale
        mid = ((end - start) / 2) + start
        vector = end - start
+        sheet_dimension = vector.length
+        if sheet_dimension < 1e-6:
+            return
        perpendicular = Vector((vector.y, -vector.x)).normalized()
-        sheet_dimension = (end - start).length

        # if annotation can't fit offset text to the right of marker
-        text_position = mid if sheet_dimension > 5 else (end + (3 * vector.normalized()))
+        if distance_override is not None:
+            text_position = end
+        else:
+            text_position = mid if sheet_dimension > 5 else (end + (3 * vector.normalized()))
        angle = math.degrees(vector.angle_signed(Vector((1, 0))))
+        # Keep text readable regardless of draw direction: if the dimension runs
+        # right-to-left the raw angle is near ±180° which renders text upside-down.
+        # Flip both angle and perpendicular so text always reads left-to-right and
+        # stays on the same side of the dimension line.
+        if abs(angle) > 90:
+            angle += 180
+            perpendicular = -perpendicular

        line = self.svg.line(start=start, end=end, class_=" ".join(classes))
        self.svg.add(line)
@@ -1585,15 +1619,20 @@ class SvgWriter:
        }

        if not show_description_only:
-            dimension = (v1_global - v0_global).length
-            dimension = helper.format_distance(
-                dimension,
-                precision=self.precision,
-                decimal_places=self.decimal_places,
-                suppress_zero_inches=suppress_zero_inches,
-                custom_unit=custom_unit,
-            )
-            text = text_prefix + str(dimension) + text_suffix
+            dimension = distance_override if distance_override is not None else (v1_global - v0_global).length
+            units_to_format = custom_units if custom_units else [None]
+            parts = [
+                helper.format_distance(
+                    dimension,
+                    precision=self.precision,
+                    decimal_places=self.decimal_places,
+                    suppress_zero_inches=suppress_zero_inches,
+                    suppress_zero_feet=suppress_zero_feet,
+                    custom_unit=unit,
+                )
+                for unit in units_to_format
+            ]
+            text = text_prefix + separator.join(str(p) for p in parts) + text_suffix
        else:
            if not dimension_text:
                return
@@ -1601,8 +1640,8 @@ class SvgWriter:

        text_tags += self.create_text_tag(
            text,
-            text_position + perpendicular,
-            box_alignment="bottom-middle",
+            text_position + perpendicular + (Vector((0, 1.5)) if distance_override is not None else Vector((0, 0))),
+            box_alignment="bottom-right" if distance_override is not None else "bottom-middle",
            multiline_to_bottom=False,
            **text_tag_kwargs,
        )
@@ -1610,8 +1649,8 @@ class SvgWriter:
        if not show_description_only and dimension_text:
            text_tags += self.create_text_tag(
                dimension_text,
-                text_position - perpendicular,
-                box_alignment="top-middle",
+                text_position - perpendicular + (Vector((0, 1.5)) if distance_override is not None else Vector((0, 0))),
+                box_alignment="top-right" if distance_override is not None else "top-middle",
                multiline_to_bottom=True,
                **text_tag_kwargs,
            )
@@ -555,6 +555,17 @@ class BIM_PT_product_assignments(Panel):

        assert self.layout
        assert (obj := context.active_object)
+
+        element = tool.Ifc.get_entity(obj)
+        if element and tool.Drawing.is_manual_drawing_reference(element):
+            row = self.layout.row(align=True)
+            fallback = "No Reference Assigned" if element.ObjectType == "REFERENCE" else "No Drawing Assigned"
+            row.label(
+                text=ProductAssignmentsData.data["relating_product"] or fallback, icon="IMAGE_DATA"
+            )
+            row.operator("bim.assign_manual_drawing_reference", icon="GREASEPENCIL", text="")
+            return
+
        props = tool.Drawing.get_object_assigned_product_props(obj)

        if props.is_editing_product:
@@ -572,6 +583,8 @@ class BIM_PT_product_assignments(Panel):
            col.enabled = bool(ProductAssignmentsData.data["relating_product"])


+
+
 def get_category_icon(category_name):
    """Get appropriate icon for each category"""
    icons = {
@@ -114,7 +114,11 @@ class AnnotationTool(WorkSpaceTool):
    bl_description = "Gives you Annotation related superpowers"
    bl_icon = os.path.join(os.path.dirname(__file__), "ops.authoring.annotation")
    bl_widget = None
-    bl_keymap = tool.Blender.get_default_selection_keypmap() + (
+    bl_keymap = (
+        # Before view3d.select: tool keymaps take priority over the addon keymap
+        # where ClickNearestDimensionAnchor is also registered.
+        ("bim.click_nearest_dimension_anchor", {"type": "LEFTMOUSE", "value": "PRESS"}, None),
+    ) + tool.Blender.get_default_selection_keypmap() + (
        ("bim.annotation_hotkey", {"type": "A", "value": "PRESS", "shift": True}, {"properties": [("hotkey", "S_A")]}),
        ("bim.annotation_hotkey", {"type": "C", "value": "PRESS", "shift": True}, {"properties": [("hotkey", "S_C")]}),
        ("bim.annotation_hotkey", {"type": "E", "value": "PRESS", "shift": True}, {"properties": [("hotkey", "S_E")]}),
@@ -221,14 +225,68 @@ class AnnotationToolUI:
        props = tool.Drawing.get_document_props()
        row.prop(props, "should_draw_decorations", text="Viewport Annotations")

+    _DIMENSION_TYPES = frozenset(("DIMENSION", "RADIUS", "DIAMETER", "ANGLE"))
+    _ELEVATION_TYPES = frozenset(("SECTION_LEVEL", "PLAN_LEVEL"))
+
    @classmethod
    def draw_edit_object_interface(cls, context):
-        if DecoratorData.get_text_data(bpy.context.active_object):
+        obj = bpy.context.active_object
+        if tool.Ifc.get_entity(obj) and DecoratorData.get_text_data(obj):
            add_layout_hotkey_operator(cls.layout, "Edit Text", "S_E", "")
        if bpy.ops.bim.copy_annotation_to_drawing.poll():
            row = cls.layout.row(align=True)
            row.operator("bim.copy_annotation_to_drawing", icon="PASTEDOWN", text="Copy To Drawing")

+        obj = context.active_object
+        element = tool.Ifc.get_entity(obj) if obj else None
+        if element and element.is_a("IfcAnnotation"):
+            ptype = ifcopenshell.util.element.get_predefined_type(element)
+            if ptype in cls._DIMENSION_TYPES:
+                cls.layout.separator()
+                ann_props = tool.Drawing.get_annotation_props()
+                if ann_props.force_perpendicular_to_face:
+                    row = cls.layout.row(align=True)
+                    row.prop(ann_props, "line_position")
+                cls.layout.separator()
+                row = cls.layout.row(align=True)
+                op = row.operator("bim.regenerate_dimensions", icon="FILE_REFRESH", text="Regenerate")
+                op.active_only = True
+
+        obj = context.active_object
+        element = tool.Ifc.get_entity(obj) if obj else None
+        if element and element.is_a("IfcAnnotation"):
+            ptype = ifcopenshell.util.element.get_predefined_type(element)
+            if ptype in cls._DIMENSION_TYPES:
+                cls.layout.separator()
+                ann_props = tool.Drawing.get_annotation_props()
+                if ann_props.force_perpendicular_to_face:
+                    row = cls.layout.row(align=True)
+                    row.prop(ann_props, "line_position")
+                cls.layout.separator()
+                row = cls.layout.row(align=True)
+                op = row.operator("bim.regenerate_dimensions", icon="FILE_REFRESH", text="Regenerate")
+                op.active_only = True
+
+                pset = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension")
+                if pset and pset.get("Anchors"):
+                    row = cls.layout.row(align=True)
+                    row.operator("bim.bake_parametric_dimension", text="Bake to Static", icon="UNLINKED")
+                else:
+                    row = cls.layout.row(align=True)
+                    row.operator("bim.make_dimension_parametric", text="Make Parametric", icon="LINKED")
+            elif ptype in cls._ELEVATION_TYPES:
+                cls.layout.separator()
+                pset = ifcopenshell.util.element.get_pset(element, "BBIM_Dimension")
+                if pset and pset.get("Anchors"):
+                    row = cls.layout.row(align=True)
+                    op = row.operator("bim.regenerate_dimensions", icon="FILE_REFRESH", text="Regenerate")
+                    op.active_only = True
+                    row = cls.layout.row(align=True)
+                    row.operator("bim.bake_parametric_dimension", text="Bake to Static", icon="UNLINKED")
+                else:
+                    row = cls.layout.row(align=True)
+                    row.operator("bim.make_dimension_parametric", text="Make Parametric", icon="LINKED")
+
    @classmethod
    def draw_type_selection_interface(cls):
        # shared by both sidebar and header
@@ -251,6 +309,13 @@ class AnnotationToolUI:

        add_layout_hotkey_operator(cls.layout, "Add", "S_A", "Create a new annotation")

+        _DIMENSION_TYPES = {"DIMENSION", "RADIUS", "DIAMETER", "ANGLE"}
+        if object_type in _DIMENSION_TYPES:
+            row = cls.layout.row(align=True)
+            row.prop(cls.props, "force_perpendicular_to_face")
+            row = cls.layout.row(align=True)
+            row.prop(cls.props, "force_parallel_to_face")
+
        if object_type in tool.Drawing.ANNOTATION_TYPES_SUPPORT_SETUP:
            row = cls.layout.row(align=True)
            row.label(text="", icon="DRIVER_ROTATIONAL_DIFFERENCE")
@@ -333,8 +398,20 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
        if created_objects:
            bpy.context.view_layer.objects.active = created_objects[-1]

+    _PARAMETRIC_DIMENSION_TYPES = frozenset(
+        ("DIMENSION", "RADIUS", "DIAMETER", "ANGLE")
+    )
+    _ELEVATION_TYPES = frozenset(("SECTION_LEVEL", "PLAN_LEVEL"))
+
    def hotkey_S_A(self):
-        if bpy.ops.bim.add_annotation.poll():
+        props = tool.Drawing.get_annotation_props()
+        if props.object_type in self._PARAMETRIC_DIMENSION_TYPES:
+            if bpy.ops.bim.draw_parametric_dimension.poll():
+                bpy.ops.bim.draw_parametric_dimension("INVOKE_DEFAULT")
+        elif props.object_type in self._ELEVATION_TYPES:
+            if bpy.ops.bim.add_elevation_annotation.poll():
+                bpy.ops.bim.add_elevation_annotation("INVOKE_DEFAULT")
+        elif bpy.ops.bim.add_annotation.poll():
            bpy.ops.bim.add_annotation()

    def hotkey_S_E(self):
@@ -1325,6 +1325,10 @@ class OverrideDuplicateMove(bpy.types.Operator):
        if new_active_obj:
            context.view_layer.objects.active = new_active_obj

+        if any(e.is_a("IfcAnnotation") for e in old_to_new):
+            import bonsai.bim.module.drawing.handler as _drawing_handler
+            _drawing_handler.invalidate_dim_index()
+
        return old_to_new


@@ -834,6 +834,8 @@ class EditMaterialSetItem(bpy.types.Operator, tool.Ifc.Operator):
            )
            slab.DumbSlabPlaner().regenerate_from_layer(layer)
            wall.DumbWallPlaner().regenerate_from_layer(layer)
+            from bonsai.bim.module.drawing.handler import regenerate_dims_for_layer
+            regenerate_dims_for_layer(self.file, layer)
        elif material.is_a("IfcMaterialProfileSet"):
            profile_def = None
            if mprops.profiles:
@@ -796,6 +796,8 @@ class PolylineDecorator(tool.Blender.ViewportDecorator):
        rv3d = region.data

        polyline_props = tool.Model.get_polyline_props()
+        if not polyline_props.snap_mouse_point:
+            return
        snap_prop = polyline_props.snap_mouse_point[0]
        mouse_point = Vector((snap_prop.x, snap_prop.y, snap_prop.z))

@@ -863,6 +865,8 @@ class PolylineDecorator(tool.Blender.ViewportDecorator):
        gpu.state.point_size_set(6)

        polyline_props = tool.Model.get_polyline_props()
+        if not polyline_props.snap_mouse_point:
+            return
        snap_prop = polyline_props.snap_mouse_point[0]
        # Point related to the mouse
        mouse_point = [Vector((snap_prop.x, snap_prop.y, snap_prop.z))]
@@ -462,14 +462,26 @@ class PolylineOperator:
        self.tool_state.axis_method = None
        self.tool_state.plane_method = None
        self.tool_state.mode = "Mouse"
-        tool.Raycast.clear_snap_objs()
+        # Do not call clear_snap_objs() here — create_snap_obj() validates stale
+        # entries per-object (vertex count + position check), so the BVH cache can
+        # safely persist across invocations. Clearing it caused an 11-second stall
+        # on every Shift+A because SnapObj rebuilds a pure-Python BVH tree.
        self.visible_objs = tool.Raycast.get_visible_objects(context)
        for obj in self.visible_objs:
            if bbox_2d := tool.Raycast.get_on_screen_2d_bounding_boxes(context, obj):
                self.objs_2d_bbox.append(bbox_2d)
-        detected_snaps = tool.Snap.detect_snapping_points(context, event, self.objs_2d_bbox, self.tool_state)
-        self.snapping_points = tool.Snap.select_snapping_points(context, event, self.tool_state, detected_snaps)
+        self._init_snapping_points(context, event)
        tool.Polyline.calculate_distance_and_angle(context, self.input_ui, self.tool_state)

        tool.Blender.update_viewport()
        context.window_manager.modal_handler_add(self)
+
+    def _init_snapping_points(self, context: bpy.types.Context, event: bpy.types.Event) -> None:
+        """Populate self.snapping_points at operator start.
+
+        Override in subclasses to skip the full BVH snap detection when a cheap
+        placeholder is sufficient.  The default runs the full detection pass.
+        """
+        detected_snaps = tool.Snap.detect_snapping_points(context, event, self.objs_2d_bbox, self.tool_state)
+        self.snapping_points = tool.Snap.select_snapping_points(context, event, self.tool_state, detected_snaps)
+
@@ -88,6 +88,44 @@ class DisablePsetEditing(bpy.types.Operator, tool.Ifc.Operator):
        props.active_pset_type = "-"


+def _regenerate_parametric_dimension(file, annotation):
+    """Regenerate a single parametric dimension annotation after a pset edit."""
+    try:
+        import json
+        import numpy as np
+        import ifcopenshell.util.element
+        import ifcopenshell.api.drawing as drawing_api
+        import bonsai.tool as _tool
+        from bonsai.bim.module.drawing.operator import _update_blender_curve
+
+        pset_data = ifcopenshell.util.element.get_pset(annotation, "BBIM_Dimension")
+        if not pset_data or not pset_data.get("Anchors"):
+            return
+
+        anchors = json.loads(pset_data["Anchors"])
+        placement_override = {}
+        for a in anchors:
+            guid = a.get("guid")
+            if not guid:
+                continue
+            try:
+                elem = file.by_guid(guid)
+                elem_obj = _tool.Ifc.get_object(elem)
+                if elem_obj:
+                    placement_override[elem.id()] = np.array(elem_obj.matrix_world)
+            except Exception:
+                pass
+
+        resolved_pts = drawing_api.regenerate_dimension(
+            file, annotation, placement_override=placement_override
+        )
+        if resolved_pts:
+            _update_blender_curve(annotation, resolved_pts)
+    except Exception:
+        import traceback
+        traceback.print_exc()
+
+
 class EditPset(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.edit_pset"
    bl_label = "Edit Pset"
@@ -152,7 +190,12 @@ class EditPset(bpy.types.Operator, tool.Ifc.Operator):
            )
            if tool.Cost.has_schedules():
                tool.Cost.update_cost_items(pset=pset)
+        is_bbim_dimension = props.active_pset_name == "BBIM_Dimension" and element.is_a("IfcAnnotation")
+
        bpy.ops.bim.disable_pset_editing(obj=self.obj, obj_type=self.obj_type)
+        if is_bbim_dimension:
+            _regenerate_parametric_dimension(self.file, element)
+
        tool.Blender.update_viewport()


@@ -542,6 +542,10 @@ def add_annotation(
        if relating_type:
            drawing_tool.run_type_assign_type(element=element, relating_type=relating_type)
        ifc.run("group.assign_group", group=drawing_tool.get_drawing_group(drawing), products=[element])
+        if object_type == "SECTION":
+            camera = ifc.get_object(drawing)
+            if camera:
+                drawing_tool.update_section_endpoints(obj, camera)
    if representation := drawing_tool.get_representation(element, context):
        drawing_tool.reload_representation(obj=obj, representation=representation)
    collector.assign(obj, should_clean_users_collection=True)
@@ -550,6 +554,26 @@ def add_annotation(
    return obj


+def assign_manual_drawing_reference(
+    ifc: type[tool.Ifc],
+    drawing_tool: type[tool.Drawing],
+    element: ifcopenshell.entity_instance,
+    drawing: Optional[ifcopenshell.entity_instance],
+) -> None:
+    for existing in drawing_tool.get_assigned_product_workaround(element):
+        ifc.run("drawing.unassign_product", relating_product=existing, related_object=element)
+    if drawing:
+        ifc.run("drawing.assign_product", relating_product=drawing, related_object=element)
+
+
+def assign_manual_reference_document(
+    drawing_tool: type[tool.Drawing],
+    element: ifcopenshell.entity_instance,
+    document: Optional[ifcopenshell.entity_instance],
+) -> None:
+    drawing_tool.set_annotation_reference_doc(element, document)
+
+
 def build_schedule(drawing: type[tool.Drawing], schedule: ifcopenshell.entity_instance) -> None:
    drawing.create_svg_schedule(schedule)
    drawing.open_svg(drawing.get_path_with_ext(drawing.get_document_uri(schedule), "svg"))
@@ -77,6 +77,8 @@ if TYPE_CHECKING:
    from bonsai.bim.module.drawing.prop import Drawing as DrawingProperties


+
+
 class Drawing(bonsai.core.tool.Drawing):
    ANNOTATION_DATA_TYPE = Literal["empty", "curve", "mesh"]
    PERSPECTIVE_CAMERA_SHIFT_PROPERTIES = ("PerspectiveShiftX", "PerspectiveShiftY")
@@ -209,6 +211,17 @@ class Drawing(bonsai.core.tool.Drawing):
            co_end = co1 + vec * scaled_length
            obj = annotation.Annotator.add_line_to_annotation(obj, co_end, co1)
            obj.matrix_world = obj.matrix_world @ Matrix.Rotation(math.radians(-90), 4, "Z")
+        elif object_type == "SECTION_LEVEL":
+            co1, _, co3, _ = annotation.Annotator.get_placeholder_coords()
+            # co3 - co1 is the camera X direction (horizontal in a section view).
+            vec = co3 - co1
+            if vec.length == 0:
+                vec = Vector((1, 0, 0))
+            else:
+                vec = vec.normalized()
+            scaled_length = 0.023 * scale
+            co_end = co1 + vec * scaled_length
+            obj = annotation.Annotator.add_line_to_annotation(obj, co_end, co1)
        elif object_type != "TEXT":
            obj = annotation.Annotator.add_line_to_annotation(obj)

@@ -1632,7 +1645,14 @@ class Drawing(bonsai.core.tool.Drawing):

    @classmethod
    def is_auto_annotation(cls, element: ifcopenshell.entity_instance):
-        return element.is_a("IfcAnnotation") and element.ObjectType in ("GRID", "SECTION", "ELEVATION", "SECTION_LEVEL")
+        if not (element.is_a("IfcAnnotation") and element.ObjectType in ("GRID", "SECTION", "ELEVATION", "SECTION_LEVEL")):
+            return False
+        if ifcopenshell.util.element.get_pset(element, "EPset_Annotation", "IsManualDrawingReference"):
+            return False
+        ptype = ifcopenshell.util.element.get_predefined_type(element)
+        if ptype in ("SECTION_LEVEL", "PLAN_LEVEL") and ifcopenshell.util.element.get_pset(element, "BBIM_Dimension"):
+            return False
+        return True

    @classmethod
    def get_drawing_reference_annotation(
@@ -1964,6 +1984,95 @@ class Drawing(bonsai.core.tool.Drawing):
            element.Name = elevation.Name or "Unnamed"
            return element

+    @classmethod
+    def create_manual_elevation_reference(cls, drawing: ifcopenshell.entity_instance) -> ifcopenshell.entity_instance:
+        cursor_location = bpy.context.scene.cursor.location.copy()
+        obj = bpy.data.objects.new("Unnamed", None)
+        obj.empty_display_size = 0.1
+        obj.matrix_world = Matrix.Translation(cursor_location) @ Matrix.Rotation(math.radians(90), 4, "X")
+        element = cls.run_root_assign_class(
+            obj=obj, ifc_class="IfcAnnotation", predefined_type="ELEVATION", should_add_representation=False
+        )
+        element.Name = "Unnamed"
+        return element
+
+    @classmethod
+    def create_manual_section_reference(
+        cls, drawing: ifcopenshell.entity_instance, context: ifcopenshell.entity_instance
+    ) -> ifcopenshell.entity_instance:
+        cursor_location = bpy.context.scene.cursor.location.copy()
+        mesh = bpy.data.meshes.new("Mesh")
+        obj = bpy.data.objects.new("Unnamed", mesh)
+        obj.matrix_world = Matrix.Translation(cursor_location)
+        element = cls.run_root_assign_class(
+            obj=obj, ifc_class="IfcAnnotation", predefined_type="SECTION", should_add_representation=False
+        )
+        element.Name = "Unnamed"
+        builder = ShapeBuilder(tool.Ifc.get())
+        unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+        p1 = cursor_location + Vector((-0.5, 0, 0))
+        p2 = cursor_location + Vector((0.5, 0, 0))
+        points = [p1 / unit_scale, p2 / unit_scale]
+        representation = builder.get_representation(context, [builder.polyline(points)])
+        ifcopenshell.api.geometry.assign_representation(tool.Ifc.get(), element, representation)
+        bonsai.core.geometry.switch_representation(tool.Ifc, tool.Geometry, obj=obj, representation=representation)
+        return element
+
+    @classmethod
+    def set_manual_drawing_reference(cls, element: ifcopenshell.entity_instance) -> None:
+        ifc_file = tool.Ifc.get()
+        pset = tool.Pset.get_element_pset(element, "EPset_Annotation")
+        if not pset:
+            pset = ifcopenshell.api.pset.add_pset(ifc_file, product=element, name="EPset_Annotation")
+        ifcopenshell.api.pset.edit_pset(ifc_file, pset=pset, properties={"IsManualDrawingReference": True})
+
+    @classmethod
+    def is_manual_drawing_reference(cls, element: ifcopenshell.entity_instance) -> bool:
+        return bool(ifcopenshell.util.element.get_pset(element, "EPset_Annotation", "IsManualDrawingReference"))
+
+    @classmethod
+    def is_document_reference(cls, element: ifcopenshell.entity_instance) -> bool:
+        """Return True if this annotation links to an external document (not a Bonsai drawing camera)."""
+        return bool(ifcopenshell.util.element.get_pset(element, "EPset_Annotation", "IsDocumentReference"))
+
+    @classmethod
+    def set_document_reference_flag(cls, element: ifcopenshell.entity_instance) -> None:
+        """Mark this annotation as pointing to an external document reference."""
+        ifc_file = tool.Ifc.get()
+        pset = tool.Pset.get_element_pset(element, "EPset_Annotation")
+        if not pset:
+            pset = ifcopenshell.api.pset.add_pset(ifc_file, product=element, name="EPset_Annotation")
+        ifcopenshell.api.pset.edit_pset(ifc_file, pset=pset, properties={"IsDocumentReference": True})
+
+    @classmethod
+    def get_annotation_reference_doc(
+        cls, element: ifcopenshell.entity_instance
+    ) -> Union[ifcopenshell.entity_instance, None]:
+        """Return the IfcDocumentInformation linked to a document-reference annotation."""
+        for rel in element.HasAssociations:
+            if rel.is_a("IfcRelAssociatesDocument"):
+                doc = rel.RelatingDocument
+                if doc.is_a("IfcDocumentInformation"):
+                    return doc
+        return None
+
+    @classmethod
+    def set_annotation_reference_doc(
+        cls,
+        element: ifcopenshell.entity_instance,
+        document: Union[ifcopenshell.entity_instance, None],
+    ) -> None:
+        """Associate (or clear) an IfcDocumentInformation on a document-reference annotation."""
+        ifc_file = tool.Ifc.get()
+        # Remove existing document associations on this annotation.
+        for rel in list(element.HasAssociations):
+            if rel.is_a("IfcRelAssociatesDocument"):
+                ifcopenshell.api.document.unassign_document(
+                    ifc_file, products=[element], document=rel.RelatingDocument
+                )
+        if document:
+            ifcopenshell.api.document.assign_document(ifc_file, products=[element], document=document)
+
    @classmethod
    def regenerate_elevation_reference_annotation(
        cls,
@@ -2810,6 +2919,156 @@ class Drawing(bonsai.core.tool.Drawing):
        numerator, denominator = scale.split("/")
        return float(numerator) / float(denominator)

+    @classmethod
+    def get_camera_dimensions(cls, camera: bpy.types.Object) -> tuple[float, float]:
+        render = bpy.context.scene.render
+        assert isinstance(camera.data, bpy.types.Camera)
+        if render.resolution_x > render.resolution_y:
+            width = camera.data.ortho_scale
+            height = width / render.resolution_x * render.resolution_y
+        else:
+            height = camera.data.ortho_scale
+            width = height / render.resolution_y * render.resolution_x
+        return width, height
+
+    @staticmethod
+    def _section_ray_rect_intersections(
+        origin: Vector, direction: Vector, half_w: float, half_h: float
+    ) -> list[float]:
+        """Return t values where the ray origin+t*direction intersects the ±half_w/±half_h rectangle."""
+        results: list[float] = []
+        eps = 1e-6
+        if abs(direction.x) > eps:
+            for x_bound in (-half_w, half_w):
+                t = (x_bound - origin.x) / direction.x
+                if abs(origin.y + t * direction.y) <= half_h + eps:
+                    results.append(t)
+        if abs(direction.y) > eps:
+            for y_bound in (-half_h, half_h):
+                t = (y_bound - origin.y) / direction.y
+                if abs(origin.x + t * direction.x) <= half_w + eps:
+                    results.append(t)
+        return results
+
+    @classmethod
+    def get_section_border_positions(
+        cls,
+        camera: bpy.types.Object,
+        v0_world: Vector,
+        v1_world: Vector,
+        border_offset_mm: float,
+    ) -> tuple[Vector, Vector]:
+        """Return world-space positions for section endpoints placed at the camera border + border_offset_mm (paper mm)."""
+        diagram_scale = cls.get_diagram_scale(camera)
+        if not diagram_scale:
+            return v0_world, v1_world
+        scale = cls.get_scale_ratio(diagram_scale["Scale"])
+        model_offset = (border_offset_mm / 1000.0) / scale
+
+        width, height = cls.get_camera_dimensions(camera)
+        half_w, half_h = width / 2, height / 2
+
+        cam_inv = camera.matrix_world.inverted()
+        v0_local = cam_inv @ v0_world
+        v1_local = cam_inv @ v1_world
+
+        origin = Vector(((v0_local.x + v1_local.x) / 2, (v0_local.y + v1_local.y) / 2))
+        dir_xy = Vector((v1_local.x - v0_local.x, v1_local.y - v0_local.y))
+        if dir_xy.length < 1e-6:
+            return v0_world, v1_world
+        dir_xy = dir_xy.normalized()
+        z = v0_local.z
+
+        t_values = cls._section_ray_rect_intersections(origin, dir_xy, half_w, half_h)
+        pos_ts = sorted(t for t in t_values if t >= 0)
+        neg_ts = sorted((t for t in t_values if t < 0), reverse=True)
+
+        if not pos_ts or not neg_ts:
+            return v0_world, v1_world
+
+        t_end = pos_ts[0]
+        t_start = neg_ts[0]
+        new_v0_local = Vector((
+            origin.x + (t_start + model_offset) * dir_xy.x,
+            origin.y + (t_start + model_offset) * dir_xy.y,
+            z,
+        ))
+        new_v1_local = Vector((
+            origin.x + (t_end - model_offset) * dir_xy.x,
+            origin.y + (t_end - model_offset) * dir_xy.y,
+            z,
+        ))
+        return camera.matrix_world @ new_v0_local, camera.matrix_world @ new_v1_local
+
+    @classmethod
+    def update_section_endpoints(cls, obj: bpy.types.Object, camera: bpy.types.Object) -> None:
+        """Move section line endpoints to camera border + BorderOffset, skipping any manually moved vertex."""
+        element = tool.Ifc.get_entity(obj)
+        if not element:
+            return
+        if not obj.data or not hasattr(obj.data, "edges") or not obj.data.edges:
+            return
+
+        pset_data = ifcopenshell.util.element.get_pset(element, "BBIM_Section") or {}
+        border_offset = float(pset_data.get("BorderOffset", 8.0))
+        if border_offset <= 0:
+            return
+
+        auto_v0 = cls._parse_vector3(pset_data.get("AutoStartPosition") or "")
+        auto_v1 = cls._parse_vector3(pset_data.get("AutoEndPosition") or "")
+
+        edge = obj.data.edges[0]
+        v0 = obj.data.vertices[edge.vertices[0]]
+        v1 = obj.data.vertices[edge.vertices[1]]
+        v0_world = obj.matrix_world @ v0.co
+        v1_world = obj.matrix_world @ v1.co
+
+        # A vertex is "auto" if it has never been auto-positioned, or still sits at the stored auto position.
+        v0_is_auto = auto_v0 is None or (v0_world - auto_v0).length < 1e-4
+        v1_is_auto = auto_v1 is None or (v1_world - auto_v1).length < 1e-4
+
+        if not v0_is_auto and not v1_is_auto:
+            return
+
+        new_v0_world, new_v1_world = cls.get_section_border_positions(camera, v0_world, v1_world, border_offset)
+
+        if v0_is_auto:
+            v0.co = obj.matrix_world.inverted() @ new_v0_world
+        if v1_is_auto:
+            v1.co = obj.matrix_world.inverted() @ new_v1_world
+        obj.data.update()
+
+        stored_v0 = new_v0_world if v0_is_auto else v0_world
+        stored_v1 = new_v1_world if v1_is_auto else v1_world
+
+        pset_id = pset_data.get("id")
+        if pset_id:
+            pset_entity = tool.Ifc.get().by_id(pset_id)
+        else:
+            pset_entity = ifcopenshell.api.pset.add_pset(tool.Ifc.get(), product=element, name="BBIM_Section")
+        ifcopenshell.api.pset.edit_pset(
+            tool.Ifc.get(),
+            pset=pset_entity,
+            properties={
+                "BorderOffset": border_offset,
+                "AutoStartPosition": cls._format_vector3(stored_v0),
+                "AutoEndPosition": cls._format_vector3(stored_v1),
+            },
+        )
+        bpy.ops.bim.update_representation(obj=obj.name, ifc_representation_class="")
+
+    @staticmethod
+    def _parse_vector3(s: str) -> Optional[Vector]:
+        try:
+            x, y, z = map(float, s.split(","))
+            return Vector((x, y, z))
+        except Exception:
+            return None
+
+    @staticmethod
+    def _format_vector3(v: Vector) -> str:
+        return f"{v.x:.6f},{v.y:.6f},{v.z:.6f}"
+
    @classmethod
    def get_diagram_scale(cls, camera: Union[bpy.types.Object, bpy.types.Camera]) -> dict[str, str]:
        props = cls.get_camera_props(camera)
@@ -970,18 +970,31 @@ class Raycast(bonsai.core.tool.Raycast):
        if obj.data is None or not isinstance(obj.data, bpy.types.Mesh):
            return None
        for i, snap_obj in enumerate(cls.snap_objs):
-            if obj.name == snap_obj.obj.name:
-                # Handle objects modified while a modal operator is active.
-                # Example: adding a door or window alters the wall geometry.
+            try:
+                cached_name = snap_obj.obj.name
+            except ReferenceError:
+                cls.snap_objs.pop(i)
+                break
+            if obj.name == cached_name:
+                # Fast O(1) invalidation: vertex count change (mesh edit) or
+                # world matrix change (object moved/rotated).
                if len(obj.data.vertices) != len(snap_obj.verts_3d):
                    cls.snap_objs.pop(i)
                    snap_obj = SnapObj(obj)
                    cls.snap_objs.append(snap_obj)
-                for v1, v2 in zip(obj.data.vertices, snap_obj.verts_3d):
-                    if (obj.matrix_world @ v1.co) != v2:
+                    return snap_obj
+                if obj.matrix_world != snap_obj.matrix_world:
+                    cls.snap_objs.pop(i)
+                    snap_obj = SnapObj(obj)
+                    cls.snap_objs.append(snap_obj)
+                    return snap_obj
+                # Sample one vertex to catch mesh edits that preserve vertex count.
+                if obj.data.vertices and snap_obj.verts_3d:
+                    if (obj.matrix_world @ obj.data.vertices[0].co) != snap_obj.verts_3d[0]:
                        cls.snap_objs.pop(i)
                        snap_obj = SnapObj(obj)
                        cls.snap_objs.append(snap_obj)
+                        return snap_obj
                return snap_obj
        snap_obj = SnapObj(obj)
        cls.snap_objs.append(snap_obj)
@@ -1020,6 +1033,7 @@ class SnapObj:
        self.root = None
        self._bvh_built = False
        self.verts_3d = [obj.matrix_world @ v.co for v in obj.data.vertices]
+        self.matrix_world = obj.matrix_world.copy()
        self.snap_points = []

    def _ensure_bvh(self):
@@ -25,12 +25,25 @@ annotations may have relationships which indicate smart data being populated.
 from .. import wrap_usecases
 from .assign_product import assign_product
 from .edit_text_literal import edit_text_literal
+from .regenerate_dimension import regenerate_dimension, get_dimension_segment_lengths
+from .resolve_anchor import build_anchor_from_hit, build_anchor_from_layer_boundary, build_anchor_from_local_point, build_anchor_from_profile_vert, build_anchor_from_profile_edge, get_layer_snap_candidates, get_profile_snap_candidates, make_world_anchor, resolve_anchor
 from .unassign_product import unassign_product

 wrap_usecases(__path__, __name__)

 __all__ = [
    "assign_product",
+    "build_anchor_from_hit",
+    "build_anchor_from_layer_boundary",
+    "build_anchor_from_local_point",
+    "build_anchor_from_profile_edge",
+    "build_anchor_from_profile_vert",
    "edit_text_literal",
+    "get_dimension_segment_lengths",
+    "get_layer_snap_candidates",
+    "get_profile_snap_candidates",
+    "make_world_anchor",
+    "regenerate_dimension",
+    "resolve_anchor",
    "unassign_product",
 ]
@@ -0,0 +1,422 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Regenerate a parametric dimension annotation from its BBIM_Dimension anchors.
+
+This module operates purely on IFC data.  It:
+  1. Reads the ``Anchors`` JSON array from the ``BBIM_Dimension`` pset on an
+     ``IfcAnnotation``.
+  2. Resolves each anchor to a world-space point (IFC project units) using
+     ``resolve_anchor``.
+  3. Computes per-segment distances and updates (or creates) the linked
+     ``IfcMetric`` + ``IfcRelAssociatesConstraint`` entities.
+  4. Returns the ordered list of resolved world-space points so that the
+     Bonsai operator layer can update the Blender curve object.
+
+Updating the Blender curve (converting IFC world coords → annotation local
+coords) is the *caller's* responsibility and does **not** happen here.
+"""
+
+from __future__ import annotations
+
+import json
+import math
+from typing import Optional
+
+import ifcopenshell
+import ifcopenshell.api.owner
+import ifcopenshell.api.pset
+import ifcopenshell.geom
+import ifcopenshell.guid
+import ifcopenshell.util.element
+
+from .resolve_anchor import resolve_anchor
+
+
+_PSET_NAME = "BBIM_Dimension"
+_METRIC_INTENT_PREFIX = "PARAMETRIC_DIMENSION_SEG_"
+
+
+def regenerate_dimension(
+    file: ifcopenshell.file,
+    annotation: ifcopenshell.entity_instance,
+    settings: Optional[ifcopenshell.geom.settings] = None,
+    shape_cache: Optional[dict] = None,
+    placement_override: Optional[dict] = None,
+    camera_dir: Optional[tuple[float, float, float]] = None,
+) -> list[tuple[float, float, float]]:
+    """Regenerate a parametric dimension from its stored anchor references.
+
+    Resolves every anchor in ``BBIM_Dimension.Anchors``, updates the
+    per-segment ``IfcMetric`` values (creating them when absent), and returns
+    the resolved world-space points in metres.
+
+    :param file: The open IFC file.
+    :param annotation: An ``IfcAnnotation`` with a ``BBIM_Dimension`` pset.
+    :param settings: Geometry settings for tessellation (shared across calls).
+    :param shape_cache: Shape cache dict (shared across calls for performance).
+    :param placement_override: Optional dict mapping element STEP id → 4×4 numpy
+        matrix (metres, row-major).  Pass ``{elem.id(): np.array(obj.matrix_world)}``
+        for each referenced element so that viewport moves not yet synced to the
+        IFC ``ObjectPlacement`` are reflected.  See ``resolve_anchor`` for details.
+    :return: Ordered list of ``(x, y, z)`` tuples, one per anchor.
+             Empty list if the pset is missing or malformed.
+    """
+    pset_data = ifcopenshell.util.element.get_pset(annotation, _PSET_NAME)
+    if not pset_data or "Anchors" not in pset_data:
+        return []
+
+    try:
+        anchors: list[dict] = json.loads(pset_data["Anchors"])
+    except (json.JSONDecodeError, TypeError):
+        return []
+
+    if not anchors:
+        return []
+
+    if shape_cache is None:
+        shape_cache = {}
+
+    resolved: list[Optional[tuple]] = []
+    for anchor in anchors:
+        pt = resolve_anchor(file, anchor, settings, shape_cache, placement_override)
+        if pt is None:
+            pt = tuple(anchor["pt"]) if anchor.get("pt") else (0.0, 0.0, 0.0)
+        resolved.append(pt)
+        anchor["pt"] = list(pt)
+
+    # ForcePerpendicularToFace: project vertices 1…n onto the line through
+    # pt[0] in the direction of anchor[0]'s face normal, so the polyline is
+    # constrained perpendicular to the face the first vertex is anchored to.
+    if pset_data.get("ForcePerpendicularToFace") and len(resolved) >= 2 and resolved[0] is not None:
+        normal = _get_anchor_face_normal_world(file, anchors[0], placement_override)
+        if normal:
+            base = resolved[0]
+            for i in range(1, len(resolved)):
+                if resolved[i] is None:
+                    continue
+                pt = resolved[i]
+                t = ((pt[0] - base[0]) * normal[0]
+                     + (pt[1] - base[1]) * normal[1]
+                     + (pt[2] - base[2]) * normal[2])
+                resolved[i] = (base[0] + t * normal[0],
+                                base[1] + t * normal[1],
+                                base[2] + t * normal[2])
+                anchors[i]["pt"] = list(resolved[i])
+
+    # ForceParallelToFace: project vertices 1…n onto the line through
+    # pt[0] in the direction cross(face_normal, camera_dir), so the polyline
+    # runs parallel to the face (perpendicular to the face normal).
+    if pset_data.get("ForceParallelToFace") and len(resolved) >= 2 and resolved[0] is not None:
+        face_normal = _get_anchor_face_normal_world(file, anchors[0], placement_override)
+        if face_normal and camera_dir:
+            fn, cd = face_normal, camera_dir
+            tang = (
+                fn[1] * cd[2] - fn[2] * cd[1],
+                fn[2] * cd[0] - fn[0] * cd[2],
+                fn[0] * cd[1] - fn[1] * cd[0],
+            )
+            mag = math.sqrt(tang[0] ** 2 + tang[1] ** 2 + tang[2] ** 2)
+            if mag > 1e-12:
+                tang = (tang[0] / mag, tang[1] / mag, tang[2] / mag)
+                base = resolved[0]
+                for i in range(1, len(resolved)):
+                    if resolved[i] is None:
+                        continue
+                    pt = resolved[i]
+                    t = ((pt[0] - base[0]) * tang[0]
+                         + (pt[1] - base[1]) * tang[1]
+                         + (pt[2] - base[2]) * tang[2])
+                    resolved[i] = (base[0] + t * tang[0],
+                                   base[1] + t * tang[1],
+                                   base[2] + t * tang[2])
+                    anchors[i]["pt"] = list(resolved[i])
+
+    pset_entity_id = pset_data.get("id")
+    if pset_entity_id:
+        pset_entity = file.by_id(pset_entity_id)
+        ifcopenshell.api.pset.edit_pset(
+            file,
+            pset=pset_entity,
+            properties={"Anchors": json.dumps(anchors)},
+        )
+
+    n_segments = len(resolved) - 1
+    if n_segments >= 1:
+        existing_metrics = _get_segment_metrics(file, annotation)
+        _sync_segment_metrics(file, annotation, resolved, existing_metrics)
+
+    # LinePosition: project all points to a fixed absolute world coordinate along the
+    # horizontal offset axis (perpendicular to the dimension direction).  Applied after
+    # the pset write so anchor["pt"] always stores the true geometry surface hit.
+    # Because it is absolute, the dimension line stays put even if the geometry moves.
+    line_position = pset_data.get("LinePosition")
+    if line_position is not None and resolved:
+        face_normal = _get_anchor_face_normal_world(file, anchors[0], placement_override)
+        offset_dir = _get_line_offset_direction(face_normal, [pt for pt in resolved if pt is not None], camera_dir)
+        if offset_dir:
+            resolved = [
+                _project_to_line_position(pt, offset_dir, float(line_position)) if pt is not None else None
+                for pt in resolved
+            ]
+
+    return [pt for pt in resolved if pt is not None]
+
+
+def get_dimension_segment_lengths(
+    file: ifcopenshell.file,
+    annotation: ifcopenshell.entity_instance,
+) -> list[float]:
+    """Return the segment lengths for a parametric dimension from stored anchor pts.
+
+    Distances are computed from the cached ``pt`` fields in ``BBIM_Dimension.Anchors``
+    (in metres, matching ifcopenshell.geom output).  Returns an empty list if the pset
+    is absent or malformed.
+    """
+    pset_data = ifcopenshell.util.element.get_pset(annotation, _PSET_NAME)
+    if not pset_data or not pset_data.get("Anchors"):
+        return []
+    try:
+        anchors: list[dict] = json.loads(pset_data["Anchors"])
+    except Exception:
+        return []
+    lengths: list[float] = []
+    for i in range(len(anchors) - 1):
+        pt_a = anchors[i].get("pt")
+        pt_b = anchors[i + 1].get("pt")
+        if pt_a and pt_b:
+            lengths.append(_dist(tuple(pt_a), tuple(pt_b)))
+        else:
+            lengths.append(0.0)
+    return lengths
+
+
+# ---------------------------------------------------------------------------
+# IfcMetric / IfcRelAssociatesConstraint management
+# ---------------------------------------------------------------------------
+
+
+def _get_segment_metrics(
+    file: ifcopenshell.file,
+    annotation: ifcopenshell.entity_instance,
+) -> dict[int, ifcopenshell.entity_instance]:
+    """Return {segment_index: IfcMetric} for all constraint rels on the annotation."""
+    metrics: dict[int, ifcopenshell.entity_instance] = {}
+    for rel in annotation.HasAssociations:
+        if not rel.is_a("IfcRelAssociatesConstraint"):
+            continue
+        intent: str = rel.Intent or ""
+        if not intent.startswith(_METRIC_INTENT_PREFIX):
+            continue
+        try:
+            seg_idx = int(intent[len(_METRIC_INTENT_PREFIX):])
+        except ValueError:
+            continue
+        constraint = rel.RelatingConstraint
+        if constraint.is_a("IfcMetric"):
+            metrics[seg_idx] = constraint
+    return metrics
+
+
+def _sync_segment_metrics(
+    file: ifcopenshell.file,
+    annotation: ifcopenshell.entity_instance,
+    resolved_pts: list[tuple],
+    existing: dict[int, ifcopenshell.entity_instance],
+) -> None:
+    """Create missing and update existing IfcMetric entities for each segment."""
+    n_segments = len(resolved_pts) - 1
+    seen_guids: set[str] = set()
+
+    # Build a lookup of which elements are at each anchor endpoint
+    pset_data = ifcopenshell.util.element.get_pset(annotation, _PSET_NAME)
+    anchors: list[dict] = []
+    if pset_data and pset_data.get("Anchors"):
+        try:
+            anchors = json.loads(pset_data["Anchors"])
+        except Exception:
+            pass
+
+    for seg_idx in range(n_segments):
+        if seg_idx in existing:
+            pass  # metric already exists; association is still valid
+        else:
+            # Create new IfcMetric + IfcRelAssociatesConstraint
+            # DataValue is IfcMetricValueSelect (entity-only SELECT in IFC4) — omit it;
+            # the measured distance is derivable from the anchor pt fields.
+            metric = file.create_entity(
+                "IfcMetric",
+                Name=f"seg_{seg_idx}",
+                ConstraintGrade="ADVISORY",
+                Benchmark="EQUALTO",
+            )
+            # Gather related products for this segment (the two anchor elements)
+            related: list[ifcopenshell.entity_instance] = [annotation]
+            for anchor_idx in (seg_idx, seg_idx + 1):
+                if anchor_idx < len(anchors):
+                    guid = anchors[anchor_idx].get("guid")
+                    if guid and guid not in seen_guids:
+                        try:
+                            elem = file.by_guid(guid)
+                            related.append(elem)
+                            seen_guids.add(guid)
+                        except Exception:
+                            pass
+
+            file.create_entity(
+                "IfcRelAssociatesConstraint",
+                GlobalId=ifcopenshell.guid.new(),
+                OwnerHistory=ifcopenshell.api.owner.create_owner_history(file),
+                Intent=f"{_METRIC_INTENT_PREFIX}{seg_idx}",
+                RelatingConstraint=metric,
+                RelatedObjects=related,
+            )
+
+    # Remove orphaned metrics for segments that no longer exist
+    for seg_idx, metric in existing.items():
+        if seg_idx >= n_segments:
+            for rel in file.get_inverse(metric):
+                if rel.is_a("IfcRelAssociatesConstraint"):
+                    file.remove(rel)
+            file.remove(metric)
+
+
+def _dist(a: tuple, b: tuple) -> float:
+    return math.sqrt((a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2 + (a[2] - b[2]) ** 2)
+
+
+def _project_to_line_position(
+    pt: tuple, offset_dir: tuple, target: float
+) -> tuple[float, float, float]:
+    """Shift *pt* along *offset_dir* so its projection onto that axis equals *target*.
+
+    Keeps every other component of the point unchanged, so only the dimension line
+    is repositioned — the measured length stays the same.
+    """
+    current = pt[0] * offset_dir[0] + pt[1] * offset_dir[1] + pt[2] * offset_dir[2]
+    delta = target - current
+    return (
+        pt[0] + delta * offset_dir[0],
+        pt[1] + delta * offset_dir[1],
+        pt[2] + delta * offset_dir[2],
+    )
+
+
+def _get_anchor_face_normal_world(
+    file: ifcopenshell.file,
+    anchor: dict,
+    placement_override: Optional[dict] = None,
+) -> Optional[tuple[float, float, float]]:
+    """Return the world-space unit face normal stored in a FACE anchor, or None.
+
+    Reads ``normal_local`` (element-local, rotation-invariant) from the anchor
+    addr and rotates it to world space via the current element placement.
+    Also accepts the legacy ``addr.fingerprint.normal_local`` format.
+    """
+    if anchor.get("type") != "FACE":
+        return None
+    guid = anchor.get("guid")
+    if not guid:
+        return None
+    try:
+        element = file.by_guid(guid)
+    except Exception:
+        return None
+
+    addr = anchor.get("addr") or {}
+    from .resolve_anchor import _rotate_local_to_world
+
+    if addr.get("method") == "LAYER_BOUNDARY":
+        import ifcopenshell.util.element as _ifc_elem
+        usage = _ifc_elem.get_material(element, should_inherit=True)
+        if not usage or not usage.is_a("IfcMaterialLayerSetUsage"):
+            return None
+        axis = (getattr(usage, "LayerSetDirection", None) or "AXIS2")
+        if axis == "AXIS1":
+            normal_local: tuple = (1.0, 0.0, 0.0)
+        elif axis == "AXIS3":
+            normal_local = (0.0, 0.0, 1.0)
+        else:
+            normal_local = (0.0, 1.0, 0.0)
+    else:
+        # FACE_NORMAL: normal_local stored in addr (new) or addr.fingerprint (legacy).
+        normal_local = addr.get("normal_local") or (addr.get("fingerprint") or {}).get("normal_local")
+        if not normal_local:
+            return None
+
+    n = _rotate_local_to_world(element, normal_local, placement_override)
+    mag = math.sqrt(n[0] ** 2 + n[1] ** 2 + n[2] ** 2)
+    return (n[0] / mag, n[1] / mag, n[2] / mag) if mag > 1e-12 else None
+
+
+def _get_line_offset_direction(
+    face_normal: Optional[tuple[float, float, float]],
+    resolved_pts: list[tuple],
+    camera_dir: Optional[tuple[float, float, float]] = None,
+) -> Optional[tuple[float, float, float]]:
+    """Return the direction to slide the dimension line (perpendicular to it, in-view).
+
+    For plan views (camera mostly vertical) uses cross(world_Z, dim_dir) —
+    unchanged from the original behaviour, so existing stored LinePosition
+    values continue to work.
+
+    For section/elevation views (camera mostly horizontal) uses
+    cross(camera_dir, dim_dir) so the offset lies in the camera's view plane.
+    This makes dragging the gizmo move the line visually up/down (or
+    left/right) rather than in/out of the screen.
+
+    Falls back to cross(face_normal, world_Z) when the dimension line is
+    nearly parallel to the reference vector (e.g. vertical elevation dims).
+    """
+    world_z = (0.0, 0.0, 1.0)
+
+    # In section/elevation (camera mostly horizontal) use camera_dir as the
+    # reference so the offset axis lies in the view plane.
+    cam_is_plan = camera_dir is None or abs(camera_dir[2]) > 0.7
+    ref = world_z if cam_is_plan else camera_dir
+
+    # Primary: cross(ref, dim_dir)
+    if len(resolved_pts) >= 2:
+        a, b = resolved_pts[0], resolved_pts[1]
+        dx, dy, dz = b[0] - a[0], b[1] - a[1], b[2] - a[2]
+        dim_mag = math.sqrt(dx * dx + dy * dy + dz * dz)
+        if dim_mag > 1e-10:
+            dim_dir = (dx / dim_mag, dy / dim_mag, dz / dim_mag)
+            d = (
+                ref[1] * dim_dir[2] - ref[2] * dim_dir[1],
+                ref[2] * dim_dir[0] - ref[0] * dim_dir[2],
+                ref[0] * dim_dir[1] - ref[1] * dim_dir[0],
+            )
+            mag = math.sqrt(d[0] ** 2 + d[1] ** 2 + d[2] ** 2)
+            if mag > 1e-6:
+                return (d[0] / mag, d[1] / mag, d[2] / mag)
+
+    # Fallback for dims parallel to ref (e.g. vertical dims in plan):
+    # cross(face_normal, world_Z)
+    if face_normal:
+        n = face_normal
+        d = (
+            n[1] * world_z[2] - n[2] * world_z[1],
+            n[2] * world_z[0] - n[0] * world_z[2],
+            n[0] * world_z[1] - n[1] * world_z[0],
+        )
+        mag = math.sqrt(d[0] ** 2 + d[1] ** 2 + d[2] ** 2)
+        if mag > 1e-6:
+            return (d[0] / mag, d[1] / mag, d[2] / mag)
+
+    return None