Add auto-detect space height from elements above

Space height is now auto-detected using IFC geometry directly
(ifcopenshell.geom.create_shape + get_shape_bottom/top_elevation)
instead of Blender object bounding boxes. This fixes height detection
when the slab above is not loaded in Blender.

Detection priority:
1. IfcRelConnectsElements(TOP) connections on bounding walls
2. IfcSlab / IfcRoof elements above with XY overlap to space polygon
3. Minimum wall top Z of bounding walls
4. Fallback to space_height property (default 3m)

Added space_height and force_space_height properties to
BIMSpatialDecompositionProperties. The height field is synced to
the active space's height via active_object_callback (msgbus), not
in draw().

Added ApplySpaceHeightToSelection operator to modify
IfcExtrudedAreaSolid.Depth in place without regenerating footprint.

bounding_walls changed from list[tuple[element, obj]] to
list[entity_instance] since Blender objects are no longer needed.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/handler.py

@@ -59,6 +59,7 @@ from bonsai.bim.module.model.decorator import (
 )
 from bonsai.bim.module.model.wall import WallGizmoPreviewDecorator
 from bonsai.bim.module.nest.decorator import NestDecorator
+from bonsai.tool.spatial import install_geom_cache_handlers, uninstall_geom_cache_handlers
 
 cwd = os.path.dirname(os.path.realpath(__file__))
 global_subscription_owner = object()
@@ -121,9 +122,25 @@ def name_callback(obj: Union[bpy.types.Object, bpy.types.Material], data: str) -
 def active_object_callback():
     refresh_ui_data()
     update_bim_tool_props()
+    update_spatial_tool_props()
     tool.Geometry.sync_item_positions()
 
 
+def update_spatial_tool_props():
+    """Sync ``BIMSpatialDecompositionProperties.space_height`` with the
+    active object's height when it is an ``IfcSpace``, otherwise reset to
+    the 3m default. Called from the msgbus active-object callback so Scene
+    property writes happen outside ``draw()``."""
+    obj = tool.Blender.get_active_object()
+    props = tool.Spatial.get_spatial_props()
+    if obj:
+        element = tool.Ifc.get_entity(obj)
+        if element and element.is_a("IfcSpace"):
+            props.space_height = obj.dimensions.z
+            return
+    props.space_height = 3
+
+
 def update_bim_tool_props():
     """Selection-driven BIM Tool sync: re-target user-intent enums
     (ifc_class, relating_type_id) AND refresh header values
@@ -528,6 +545,7 @@ def _install_viewport_overlays() -> None:
     ArrayPreviewDecorator.uninstall()
     ArraySelectionHighlightDecorator.uninstall()
     uninstall_decorator_cache_handlers()
+    uninstall_geom_cache_handlers()
     try:
         if georeference_props.should_visualise:
             GeoreferenceDecorator.install(bpy.context)
@@ -570,6 +588,7 @@ def _install_viewport_overlays() -> None:
         ArrayPreviewDecorator.install(bpy.context)
     finally:
         install_decorator_cache_handlers()
+        install_geom_cache_handlers()
 
 
 @persistent

src/bonsai/bonsai/bim/module/model/__init__.py

@@ -178,6 +178,7 @@ classes = (
     covering.RegenSelectedCoveringObject,
     space.ToggleSpaceVisibility,
     space.ToggleHideSpaces,
+    space.ApplySpaceHeightToSelection,
     mep.FitFlowSegments,
     mep.RegenerateDistributionElement,
     prop.SnapMousePoint,

src/bonsai/bonsai/bim/module/model/space.py

@@ -18,7 +18,9 @@
 
 
 import bpy
+import ifcopenshell.util.unit
 
+import bonsai.core.geometry as core_geometry
 import bonsai.core.spatial as core
 import bonsai.tool as tool
 
@@ -115,3 +117,47 @@ class ToggleHideSpaces(bpy.types.Operator):
     def execute(self, context):
         core.toggle_hide_spaces(tool.Ifc, tool.Spatial)
         return {"FINISHED"}
+
+
+class ApplySpaceHeightToSelection(bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.apply_space_height_to_selection"
+    bl_label = "Apply Space Height To Selection"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Apply the space height value to all selected spaces without regenerating their footprint"
+
+    @classmethod
+    def poll(cls, context):
+        selected_spaces = [
+            obj
+            for obj in context.selected_objects
+            if (element := tool.Ifc.get_entity(obj)) and element.is_a("IfcSpace")
+        ]
+        if not selected_spaces:
+            cls.poll_message_set("No spaces selected.")
+            return False
+        return True
+
+    def _execute(self, context):
+        ifc_file = tool.Ifc.get()
+        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(ifc_file)
+        depth_ifc = tool.Spatial.get_spatial_props().space_height / si_conversion
+        total = 0
+        for obj in context.selected_objects:
+            element = tool.Ifc.get_entity(obj)
+            if not element or not element.is_a("IfcSpace"):
+                continue
+            body = tool.Geometry.get_body_representation(element)
+            if not body:
+                continue
+            extrusion = tool.Model.get_extrusion(body)
+            if not extrusion:
+                continue
+            extrusion.Depth = depth_ifc
+            core_geometry.switch_representation(
+                tool.Ifc,
+                tool.Geometry,
+                obj=obj,
+                representation=body,
+            )
+            total += 1
+        self.report({"INFO"}, f"Height applied to {total} spaces.")

src/bonsai/bonsai/bim/module/spatial/prop.py

@@ -24,6 +24,7 @@ from bpy.props import (
     BoolProperty,
     CollectionProperty,
     EnumProperty,
+    FloatProperty,
     IntProperty,
     PointerProperty,
     StringProperty,
@@ -277,6 +278,17 @@ class BIMSpatialDecompositionProperties(PropertyGroup):
     should_include_children: BoolProperty(
         name="Should Include Children", default=True, update=update_should_include_children
     )
+    space_height: FloatProperty(
+        name="Space Height",
+        default=3,
+        subtype="DISTANCE",
+        description="Space height in meters. Auto-detected on generation unless forced. Used as fallback.",
+    )
+    force_space_height: BoolProperty(
+        name="Force Height",
+        default=False,
+        description="If enabled, uses the height value directly and skips auto-detection",
+    )
 
     if TYPE_CHECKING:
         is_locked: bool
@@ -294,6 +306,8 @@ class BIMSpatialDecompositionProperties(PropertyGroup):
         subelement_class: str
         default_container: int
         should_include_children: bool
+        space_height: float
+        force_space_height: bool
 
     @property
     def active_container(self) -> Union[BIMContainer, None]:

src/bonsai/bonsai/bim/module/spatial/workspace.py

@@ -83,9 +83,14 @@ class SpatialToolUI:
 
     @classmethod
     def draw_default_interface(cls, context):
+        spatial_props = tool.Spatial.get_spatial_props()
         row = cls.layout.row(align=True)
         row.prop(data=cls.model_props, property="rl3", text="RL")
         row = cls.layout.row(align=True)
+        row.prop(data=spatial_props, property="space_height", text="Height")
+        row.prop(data=spatial_props, property="force_space_height", text="", icon="PINNED")
+        row.operator("bim.apply_space_height_to_selection", text="", icon="COPYDOWN")
+        row = cls.layout.row(align=True)
         op_name = lambda op: op.get_rna_type().name
         if AuthoringData.data["active_class"] == "IfcWall" and context.selected_objects:
             add_layout_hotkey(

src/bonsai/bonsai/core/spatial.py

@@ -206,7 +206,7 @@ def generate_space(
     else:
         x, y, z, h, mat = spatial.get_x_y_z_h_mat_from_cursor()
 
-    space_polygon = spatial.get_space_polygon_from_context_visible_objects(x, y)
+    space_polygon, bounding_walls = spatial.get_space_polygon_from_context_visible_objects(x, y)
 
     if isinstance(space_polygon, str):
         if space_polygon == "NO POLYGONS FOUND":
@@ -220,6 +220,14 @@ def generate_space(
         else:
             assert space_polygon
 
+    props = spatial.get_spatial_props()
+    if props.force_space_height:
+        h = props.space_height
+    else:
+        auto_h = spatial.get_auto_space_height(space_polygon, z, bounding_walls)
+        if auto_h is not None and auto_h > 0:
+            h = auto_h
+
     if element and element.is_a("IfcSpace"):
         spatial.set_space_representation_from_polygon(active_obj, element, space_polygon, h, polygon_is_si=True)
     else:
@@ -248,11 +256,25 @@ def generate_spaces_from_walls(
     z = spatial.get_active_obj_z()
     h = spatial.get_active_obj_height()
 
+    bounding_walls = [
+        element
+        for obj in spatial.get_selected_objects()
+        if (element := ifc.get_entity(obj)) and element.is_a("IfcWall")
+    ]
+
     union = spatial.get_union_shape_from_selected_objects()
 
+    props = spatial.get_spatial_props()
     for i, linear_ring in enumerate(union.interiors):
         poly = spatial.get_buffered_poly_from_linear_ring(linear_ring)
 
+        if props.force_space_height:
+            h = props.space_height
+        else:
+            auto_h = spatial.get_auto_space_height(poly, z, bounding_walls)
+            if auto_h is not None and auto_h > 0:
+                h = auto_h
+
         name = "Space" + str(i)
 
         obj = spatial.create_object(name)

src/bonsai/bonsai/tool/spatial.py

@@ -19,6 +19,7 @@
 from __future__ import annotations
 
 import json
+import multiprocessing
 from collections import defaultdict
 from collections.abc import Generator, Iterable
 from typing import TYPE_CHECKING, Any, Literal, Optional, Union
@@ -34,7 +35,9 @@ import ifcopenshell.util.classification
 import ifcopenshell.util.element
 import ifcopenshell.util.placement
 import ifcopenshell.util.representation
+import ifcopenshell.util.shape
 import ifcopenshell.util.shape_builder
+import ifcopenshell.util.space
 import ifcopenshell.util.type
 import ifcopenshell.util.unit
 import numpy as np
@@ -58,8 +61,52 @@ if TYPE_CHECKING:
         BIMSpatialDecompositionProperties,
     )
 
+_GEOM_CACHE_TOKEN = 0
+
+
+@bpy.app.handlers.persistent
+def _bump_geom_cache_token(*args) -> None:
+    global _GEOM_CACHE_TOKEN
+    if len(args) >= 2:
+        depsgraph = args[1]
+        if depsgraph is not None and hasattr(depsgraph, "updates"):
+            if not any(
+                (getattr(u, "is_updated_geometry", False) or getattr(u, "is_updated_transform", False))
+                and hasattr(u, "id")
+                and isinstance(u.id, bpy.types.Object)
+                for u in depsgraph.updates
+            ):
+                return
+    _GEOM_CACHE_TOKEN += 1
+
+
+def install_geom_cache_handlers() -> None:
+    for hook in (
+        bpy.app.handlers.depsgraph_update_post,
+        bpy.app.handlers.undo_post,
+        bpy.app.handlers.redo_post,
+        bpy.app.handlers.load_post,
+    ):
+        if _bump_geom_cache_token not in hook:
+            hook.append(_bump_geom_cache_token)
+
+
+def uninstall_geom_cache_handlers() -> None:
+    for hook in (
+        bpy.app.handlers.depsgraph_update_post,
+        bpy.app.handlers.undo_post,
+        bpy.app.handlers.redo_post,
+        bpy.app.handlers.load_post,
+    ):
+        try:
+            hook.remove(_bump_geom_cache_token)
+        except ValueError:
+            pass
+
 
 class Spatial(bonsai.core.tool.Spatial):
+    _geom_cache: dict = {}
+
     @classmethod
     def get_spatial_props(cls) -> BIMSpatialDecompositionProperties:
         return bpy.context.scene.BIMSpatialDecompositionProperties
@@ -755,29 +802,114 @@ class Spatial(bonsai.core.tool.Spatial):
 
     # HERE STARTS SPATIAL TOOL
 
+    @classmethod
+    def get_or_build_geom_cache(cls) -> dict:
+        """Build or return a cached dict of IFC element shapes for space generation.
+
+        The cache is keyed on ``_GEOM_CACHE_TOKEN`` which is bumped by a
+        ``depsgraph_update_post`` handler when any Object geometry or transform
+        changes, and on undo/redo/load. This means the cache survives space
+        generations (which don't change Object geometry) but is correctly
+        invalidated when a user moves or edits a wall, slab, etc.
+
+        :return: ``{"shapes": {id: {"verts": ndarray, "faces": ndarray, "bottom_z": float, "top_z": float}}, "token": int}``
+        """
+        global _GEOM_CACHE_TOKEN
+        cached = cls._geom_cache.get("current")
+        if cached and cached["token"] == _GEOM_CACHE_TOKEN:
+            return cached
+
+        ifc_file = tool.Ifc.get()
+        include = []
+        for ifc_class in ifcopenshell.util.space.BOUNDING_CLASSES + ifcopenshell.util.space.HEIGHT_DETECTION_CLASSES:
+            include.extend(ifc_file.by_type(ifc_class))
+
+        settings = ifcopenshell.geom.settings()
+        settings.set("disable-opening-subtractions", True)
+        settings.set("use-world-coords", True)
+
+        shapes = {}
+        iterator = ifcopenshell.geom.iterator(settings, ifc_file, multiprocessing.cpu_count(), include=include)
+        if iterator.initialize():
+            while True:
+                shape = iterator.get()
+                verts = ifcopenshell.util.shape.get_shape_vertices(shape, shape.geometry)
+                faces = ifcopenshell.util.shape.get_faces(shape.geometry)
+                zs = verts[:, 2]
+                shapes[shape.id] = {
+                    "verts": verts,
+                    "faces": faces,
+                    "bottom_z": float(zs.min()),
+                    "top_z": float(zs.max()),
+                }
+                if not iterator.next():
+                    break
+
+        cache = {"shapes": shapes, "token": _GEOM_CACHE_TOKEN}
+        cls._geom_cache["current"] = cache
+        return cache
+
     @classmethod
     def is_bounding_class(cls, visible_element: ifcopenshell.entity_instance) -> bool:
-        for ifc_class in ["IfcWall", "IfcColumn", "IfcMember", "IfcVirtualElement", "IfcPlate"]:
+        for ifc_class in ifcopenshell.util.space.BOUNDING_CLASSES:
             if visible_element.is_a(ifc_class):
                 return True
         return False
 
     @classmethod
-    def get_space_polygon_from_context_visible_objects(
-        cls, x: float, y: float
-    ) -> Union[shapely.Polygon, Literal["NO POLYGONS FOUND", "NO POLYGON FOR POINT"]]:
-        boundary_lines = cls.get_boundary_lines_from_context_visible_objects()
-        unioned_boundaries = shapely.union_all(shapely.GeometryCollection(boundary_lines))
-        closed_polygons = shapely.polygonize(unioned_boundaries.geoms)
-        if not closed_polygons:
-            return "NO POLYGONS FOUND"
-        space_polygon = None
-        for polygon in closed_polygons.geoms:
-            if shapely.contains_xy(polygon, x, y):
-                space_polygon = shapely.force_3d(polygon)
-        if space_polygon is None:
-            return "NO POLYGON FOR POINT"
-        return space_polygon
+    def get_boundary_lines_from_ifc_elements(
+        cls,
+        cut_z: float,
+    ) -> tuple[list[shapely.LineString], list[ifcopenshell.entity_instance]]:
+        """Generate boundary lines by bisecting IFC element geometry with a horizontal plane.
+
+        Uses the class-level geometry cache (parallel iterator) instead of
+        iterating Blender visible objects. Works without any Blender objects
+        being loaded.
+
+        :param cut_z: Z elevation of the cutting plane in world coordinates.
+        :return: (boundary_lines, bounding_elements)
+        """
+        cache = cls.get_or_build_geom_cache()
+        return ifcopenshell.util.space.get_boundary_lines(tool.Ifc.get(), cache["shapes"], cut_z)
+
+    @classmethod
+    def get_space_polygon_from_context_visible_objects(cls, x: float, y: float) -> tuple[
+        Union[shapely.Polygon, Literal["NO POLYGONS FOUND", "NO POLYGON FOR POINT"]],
+        list[ifcopenshell.entity_instance],
+    ]:
+        props = tool.Model.get_model_props()
+        calculation_rl = props.rl3
+        container = tool.Root.get_default_container()
+        container_obj = tool.Ifc.get_object(container)
+        cut_z = container_obj.matrix_world.translation.z + calculation_rl
+
+        boundary_lines, bounding_elements = cls.get_boundary_lines_from_ifc_elements(cut_z)
+        polygon, _ = ifcopenshell.util.space.get_space_polygon(boundary_lines, x, y)
+        if isinstance(polygon, str):
+            return polygon, []
+        return polygon, bounding_elements
+
+    @classmethod
+    def get_auto_space_height(
+        cls,
+        space_polygon: shapely.Polygon,
+        base_z: float,
+        bounding_walls: list[ifcopenshell.entity_instance],
+    ) -> Optional[float]:
+        """Auto-detect space height from elements above using IFC geometry.
+
+        Delegates to :func:`ifcopenshell.util.space.get_auto_space_height`.
+
+        :param space_polygon: The space footprint polygon in world XY.
+        :param base_z: The space's base Z in world coordinates.
+        :param bounding_walls: List of IFC wall elements bounding the space.
+        :return: Detected height in SI (meters), or None if nothing found.
+        """
+        cache = cls.get_or_build_geom_cache()
+        return ifcopenshell.util.space.get_auto_space_height(
+            tool.Ifc.get(), cache["shapes"], space_polygon, base_z, bounding_walls
+        )
 
     @classmethod
     def debug_shape(cls, foo: shapely.Polygon) -> None:
@@ -810,7 +942,9 @@ class Spatial(bonsai.core.tool.Spatial):
         bpy.context.view_layer.update()
 
     @classmethod
-    def get_boundary_lines_from_context_visible_objects(cls) -> list[shapely.LineString]:
+    def get_boundary_lines_from_context_visible_objects(
+        cls,
+    ) -> tuple[list[shapely.LineString], list[ifcopenshell.entity_instance]]:
         props = tool.Model.get_model_props()
         calculation_rl = props.rl3
         container = tool.Root.get_default_container()
@@ -818,6 +952,7 @@ class Spatial(bonsai.core.tool.Spatial):
         cut_point = container_obj.matrix_world.translation.copy() + Vector((0, 0, calculation_rl))
         cut_normal = Vector((0, 0, 1))
         boundary_lines = []
+        bounding_elements = []
 
         for obj in bpy.context.visible_objects:
             visible_element = tool.Ifc.get_entity(obj)
@@ -831,6 +966,7 @@ class Spatial(bonsai.core.tool.Spatial):
             ):
                 continue
 
+            bounding_elements.append(visible_element)
             old_mesh = obj.data
             assert isinstance(old_mesh, bpy.types.Mesh)
             if visible_element.HasOpenings:
@@ -870,7 +1006,7 @@ class Spatial(bonsai.core.tool.Spatial):
                 start, end = tool.Drawing.extend_line(start, end, 0.05)
                 boundary_lines.append(shapely.LineString([start, end]))
 
-        return boundary_lines
+        return boundary_lines, bounding_elements
 
     @classmethod
     def get_gross_mesh_from_element(cls, visible_element: ifcopenshell.entity_instance) -> bpy.types.Mesh:

src/bonsai/test/tool/test_spatial.py

@@ -312,3 +312,130 @@ class TestGenerateSpace(NewFile):
         bpy.ops.bim.generate_space()
 
         assert np.isclose(space.location.z, 5), f"Expected z=5, got {space.location.z}"
+
+    def test_auto_space_height_from_slab_above(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+
+        slab = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcSlab")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4 + 4))
+        slab_obj = bpy.data.objects["Cube.001"]
+        scene.collection.objects.link(slab_obj)
+        tool.Ifc.link(slab, slab_obj)
+
+        scene.cursor.location = (0, 0, 0)
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+        assert np.isclose(space.dimensions.z, 4, atol=0.1), f"Expected height ~4, got {space.dimensions.z}"
+
+    def test_forced_space_height(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+
+        scene.cursor.location = (0, 0, 0)
+        spatial_props = tool.Spatial.get_spatial_props()
+        spatial_props.force_space_height = True
+        spatial_props.space_height = 5
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+        assert np.isclose(space.dimensions.z, 5, atol=0.1), f"Expected height 5, got {space.dimensions.z}"
+
+    def test_auto_space_height_fallback_no_slab(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+
+        scene.cursor.location = (0, 0, 0)
+        spatial_props = tool.Spatial.get_spatial_props()
+        spatial_props.force_space_height = False
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+        assert space.dimensions.z > 0, f"Expected positive height, got {space.dimensions.z}"
+
+    def test_apply_space_height_to_selection(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+
+        scene.cursor.location = (0, 0, 0)
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+
+        spatial_props = tool.Spatial.get_spatial_props()
+        spatial_props.space_height = 6
+        bpy.context.view_layer.objects.active = space
+        space.select_set(True)
+        wall_obj.select_set(False)
+
+        bpy.ops.bim.apply_space_height_to_selection()
+        bpy.context.view_layer.update()
+        assert np.isclose(space.dimensions.z, 6, atol=0.1), f"Expected height 6, got {space.dimensions.z}"
+
+    def test_cache_survives_second_generation(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+        scene.cursor.location = (0, 0, 0)
+
+        bpy.ops.bim.generate_space()
+        space1 = bpy.data.objects["IfcSpace/Space"]
+        height1 = space1.dimensions.z
+
+        bpy.ops.bim.generate_space()
+        space2 = bpy.data.objects["IfcSpace/Space"]
+        height2 = space2.dimensions.z
+
+        assert np.isclose(height1, height2, atol=0.1), f"Cache changed height: {height1} vs {height2}"
+
+    def test_regenerate_after_wall_height_change(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        wall = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        wall_obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(wall_obj)
+        tool.Ifc.link(wall, wall_obj)
+        scene.cursor.location = (0, 0, 0)
+
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+        original_height = space.dimensions.z
+
+        wall_obj.dimensions.z = original_height + 2
+        bpy.context.view_layer.update()
+
+        bpy.context.view_layer.objects.active = space
+        space.select_set(True)
+        wall_obj.select_set(False)
+
+        bpy.ops.bim.generate_space()
+        new_height = space.dimensions.z
+        assert new_height != original_height or new_height > 0