#1153. Section references are now auto generated when activating a drawing.

src/blenderbim/blenderbim/bim/module/drawing/decoration.py

@@ -40,7 +40,7 @@ class BaseDecorator:
 
     DEF_GLSL = """
         #define PI 3.141592653589793
-        #define MAX_POINTS 32
+        #define MAX_POINTS 64
         #define CIRCLE_SEGS 12
     """
 
@@ -1162,15 +1162,13 @@ class ElevationDecorator(LevelDecorator):
 
         vec4 p0w = CLIP2WIN(p0), p1w = CLIP2WIN(p1);
         vec4 edge = p1w - p0w, dir = normalize(edge);
-        // vec4 dir = normalize(vec4(1, 0, 0, 0));
-        vec4 gap = dir * viewportDrawingScale * TRIANGLE_L * .5;
         vec4 side = vec4(cross(vec3(dir.xy, 0), vec3(0, 0, 1)).xy, 0, 0);
         vec4 p;
 
         vec4 head[CIRCLE_SEGS];
         circle_head(viewportDrawingScale * CIRCLE_SIZE, head);
 
-        vec4 head3[5];
+        vec4 head5[5];
 
         // start edge circle
         for(int i=0; i<CIRCLE_SEGS; i++) {
@@ -1183,21 +1181,21 @@ class ElevationDecorator(LevelDecorator):
         EmitVertex();
         EndPrimitive();
 
-        // start edge triangle
-        triangle_head(side, dir, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, viewportDrawingScale * CIRCLE_SIZE, head3);
-        p = p0w + head3[0];
+        // edge triangle
+        triangle_head(side, dir, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, viewportDrawingScale * CIRCLE_SIZE, head5);
+        p = p0w + head5[0];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[1];
+        p = p0w + head5[1];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[2];
+        p = p0w + head5[2];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[3];
+        p = p0w + head5[3];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[4];
+        p = p0w + head5[4];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
@@ -1220,15 +1218,15 @@ class ElevationDecorator(LevelDecorator):
         self.draw_lines(context, obj, [v1, v2], [(0, 1)])
 
 
-class SectionViewDecorator(LevelDecorator):
+class SectionDecorator(LevelDecorator):
     objecttype = "SECTION"
 
     DEF_GLSL = (
         BaseDecorator.DEF_GLSL
         + """
         #define CIRCLE_SIZE 8.0
-        #define TRIANGLE_L 32.0
-        #define TRIANGLE_W 16.0
+        #define TRIANGLE_L 22.63
+        #define TRIANGLE_W 11.31
     """
     )
 
@@ -1239,12 +1237,14 @@ class SectionViewDecorator(LevelDecorator):
     layout(lines) in;
     layout(line_strip, max_vertices=MAX_POINTS) out;
 
-    void triangle_head(in vec4 dir, in vec4 side, in float length, in float width, out vec4 head[3]) {
-        vec4 nose = dir * length;
-        vec4 ear = side * width;
-        head[0] = vec4(0);
-        head[1] = nose * .5 + ear;
-        head[2] = nose;
+    void triangle_head(in vec4 side, in vec4 dir, in float length, in float width, in float radius, out vec4 head[5]) {
+        vec4 nose = side * length;
+        vec4 ear = dir * width;
+        head[0] = side * -radius;
+        head[1] = nose * -.5;
+        head[2] = vec4(0) + ear;
+        head[3] = nose * .5;
+        head[4] = side * radius;
     }
 
     void main() {
@@ -1254,76 +1254,114 @@ class SectionViewDecorator(LevelDecorator):
         vec4 p0 = gl_in[0].gl_Position, p1 = gl_in[1].gl_Position;
 
         vec4 p0w = CLIP2WIN(p0), p1w = CLIP2WIN(p1);
-        vec4 edge = p1w - p0w, dir = normalize(edge);
-        vec4 gap = dir * viewportDrawingScale * TRIANGLE_L * .5;
-        vec4 side = vec4(cross(vec3(dir.xy, 0), vec3(0, 0, 1)).xy, 0, 0);
+        vec4 edge = p1w - p0w, side = normalize(edge);
+        vec4 gap = side * viewportDrawingScale * CIRCLE_SIZE;
+        vec4 dir = vec4(cross(vec3(side.xy, 0), vec3(0, 0, 1)).xy, 0, 0);
         vec4 p;
 
         vec4 head[CIRCLE_SEGS];
         circle_head(viewportDrawingScale * CIRCLE_SIZE, head);
 
-        vec4 head3[3];
+        vec4 head5[5];
 
         // start edge circle
         for(int i=0; i<CIRCLE_SEGS; i++) {
-            p = p0w + gap + head[i];
+            p = p0w + head[i];
             gl_Position = WIN2CLIP(p);
             EmitVertex();
         }
-        p = p0w + gap + head[0];
+        p = p0w + head[0];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
 
         // start edge triangle
-        triangle_head(dir, -side, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, head3);
-        p = p0w + head3[0];
+        triangle_head(side, dir, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, viewportDrawingScale * CIRCLE_SIZE, head5);
+        p = p0w + head5[0];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[1];
+        p = p0w + head5[1];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p0w + head3[2];
+        p = p0w + head5[2];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p0w + head5[3];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p0w + head5[4];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        EndPrimitive();
+
+        // start reference divider
+        p = p0w + normalize(vec4(-1, 0, 0, 0)) * viewportDrawingScale * CIRCLE_SIZE;
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p0w + normalize(vec4(1, 0, 0, 0)) * viewportDrawingScale * CIRCLE_SIZE;
         gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
 
         // end edge circle
         for(int i=0; i<CIRCLE_SEGS; i++) {
-            p = p1w - gap + head[i];
+            p = p1w - head[i];
             gl_Position = WIN2CLIP(p);
             EmitVertex();
         }
-        p = p1w - gap + head[0];
+        p = p1w - head[0];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
 
         // end edge triangle
-        triangle_head(-dir, -side, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, head3);
-        p = p1w + head3[0];
+        triangle_head(side, dir, viewportDrawingScale * TRIANGLE_L, viewportDrawingScale * TRIANGLE_W, viewportDrawingScale * CIRCLE_SIZE, head5);
+        p = p1w + head5[0];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p1w + head3[1];
+        p = p1w + head5[1];
         gl_Position = WIN2CLIP(p);
         EmitVertex();
-        p = p1w + head3[2];
+        p = p1w + head5[2];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p1w + head5[3];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p1w + head5[4];
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        EndPrimitive();
+
+        // end reference divider
+        p = p1w + normalize(vec4(-1, 0, 0, 0)) * viewportDrawingScale * CIRCLE_SIZE;
+        gl_Position = WIN2CLIP(p);
+        EmitVertex();
+        p = p1w + normalize(vec4(1, 0, 0, 0)) * viewportDrawingScale * CIRCLE_SIZE;
         gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
 
         // stem
-        gl_Position = p0;
+        p = p0w + gap;
+        gl_Position = WIN2CLIP(p);
         EmitVertex();
-        gl_Position = p1;
+        p = p1w - gap;
+        gl_Position = WIN2CLIP(p);
         EmitVertex();
         EndPrimitive();
     }
     """
 
     def decorate(self, context, obj):
-        verts, _, _ = self.get_path_geom(obj, topo=False)
-        self.draw_lines(context, obj, verts, [(0, 1)])
+        if obj.data.is_editmode:
+            verts, idxs = self.get_editmesh_geom(obj)
+        else:
+            verts, idxs = self.get_mesh_geom(obj)
+        vert_map = {v.freeze(): (obj.matrix_world.inverted() @ v).x for v in verts}
+        verts = sorted(verts, key=lambda v: vert_map[v], reverse=True)
+        self.draw_lines(context, obj, verts, idxs)
+
 
 
 class TextDecorator(BaseDecorator):
@@ -1422,7 +1460,7 @@ class DecorationsHandler:
         SectionLevelDecorator,
         StairDecorator,
         BreakDecorator,
-        SectionViewDecorator,
+        SectionDecorator,
         ElevationDecorator,
         TextDecorator,
     ]

src/blenderbim/blenderbim/bim/module/drawing/helper.py

@@ -260,14 +260,11 @@ def format_distance(value, isArea=False, hide_units=True):
 def get_active_drawing(scene):
     """Get active drawing collection and camera"""
     props = scene.DocProperties
-    if props.active_drawing_index is None or len(props.drawings) == 0:
-        return None, None
     try:
-        drawing = props.active_drawing
-        camera = tool.Ifc.get_object(tool.Ifc.get().by_id(drawing.ifc_definition_id))
+        camera = tool.Ifc.get_object(tool.Ifc.get().by_id(props.active_drawing_id))
         return camera.users_collection[0], camera
-    except (KeyError, IndexError):
-        raise RuntimeError("missing drawing collection")
+    except:
+        return None, None
 
 
 def get_project_collection(scene):

src/blenderbim/blenderbim/bim/module/drawing/operator.py

@@ -82,6 +82,11 @@ class AddDrawing(bpy.types.Operator, Operator):
             target_view=self.props.target_view,
             location_hint=hint,
         )
+        try:
+            drawing = tool.Ifc.get().by_id(self.props.active_drawing_id)
+            core.sync_references(tool.Ifc, tool.Collector, tool.Drawing, drawing=drawing)
+        except:
+            pass
 
 
 class CreateDrawing(bpy.types.Operator):
@@ -777,12 +782,10 @@ class RemoveDrawing(bpy.types.Operator, Operator):
     bl_idname = "bim.remove_drawing"
     bl_label = "Remove Drawing"
     bl_options = {"REGISTER", "UNDO"}
-    index: bpy.props.IntProperty()
+    drawing: bpy.props.IntProperty()
 
     def _execute(self, context):
-        props = context.scene.DocProperties
-        drawing = tool.Ifc.get().by_id(props.drawings[self.index].ifc_definition_id)
-        core.remove_drawing(tool.Ifc, tool.Drawing, drawing=drawing)
+        core.remove_drawing(tool.Ifc, tool.Drawing, drawing=tool.Ifc.get().by_id(self.drawing))
 
 
 class AddDrawingStyle(bpy.types.Operator):

src/blenderbim/blenderbim/bim/module/drawing/prop.py

@@ -293,6 +293,7 @@ class DocProperties(PropertyGroup):
     )
     location_hint: EnumProperty(items=get_location_hint, name="Location Hint")
     drawings: CollectionProperty(name="Drawings", type=Drawing)
+    active_drawing_id: IntProperty(name="Active Drawing Id")
     active_drawing_index: IntProperty(name="Active Drawing Index")
     current_drawing_index: IntProperty(name="Current Drawing Index")
     schedules: CollectionProperty(name="Schedules", type=Schedule)
@@ -312,10 +313,6 @@ class DocProperties(PropertyGroup):
     def active_schedule(self):
         return self.schedules[self.active_schedule_index]
 
-    @property
-    def active_drawing(self):
-        return self.drawings[self.active_drawing_index]
-
     @property
     def active_sheet(self):
         return self.sheets[self.active_sheet_index]

src/blenderbim/blenderbim/bim/module/drawing/ui.py

@@ -172,14 +172,15 @@ class BIM_PT_drawings(Panel):
 
         if self.props.drawings:
             if self.props.active_drawing_index < len(self.props.drawings):
+                active_drawing = self.props.drawings[self.props.active_drawing_index]
                 row = self.layout.row(align=True)
                 row.alignment = "RIGHT"
                 op = row.operator("bim.open_view", icon="URL", text="")
-                op.view = self.props.active_drawing.name
+                op.view = active_drawing.name
                 op = row.operator("bim.activate_view", icon="OUTLINER_OB_CAMERA", text="")
-                op.drawing = self.props.active_drawing.ifc_definition_id
+                op.drawing = active_drawing.ifc_definition_id
                 row.operator("bim.create_drawing", text="", icon="OUTPUT")
-                row.operator("bim.remove_drawing", icon="X", text="").index = self.props.active_drawing_index
+                row.operator("bim.remove_drawing", icon="X", text="").drawing = active_drawing.ifc_definition_id
             self.layout.template_list(
                 "BIM_UL_drawinglist", "", self.props, "drawings", self.props, "active_drawing_index"
             )

src/blenderbim/blenderbim/tool/drawing.py

@@ -413,60 +413,15 @@ class Drawing(blenderbim.core.tool.Drawing):
             target_view = psets.get("EPset_Drawing", {}).get("TargetView", None)
             if target_view == "ELEVATION_VIEW":
                 return cls.generate_elevation_reference_annotation(drawing, reference_element, context)
+            elif target_view == "SECTION_VIEW":
+                return cls.generate_section_reference_annotation(drawing, reference_element, context)
 
     @classmethod
-    def generate_elevation_reference_annotation(cls, drawing, reference_element, context):
+    def generate_section_reference_annotation(cls, drawing, reference_element, context):
         reference_obj = tool.Ifc.get_object(reference_element)
         reference_obj.matrix_world
         camera = tool.Ifc.get_object(drawing)
-
-        def is_perpendicular(a, b):
-            axes = [mathutils.Vector((1, 0, 0)), mathutils.Vector((0, 1, 0)), mathutils.Vector((0, 0, 1))]
-            a_quaternion = a.matrix_world.to_quaternion()
-            b_quaternion = b.matrix_world.to_quaternion()
-            for axis in axes:
-                if abs((a_quaternion @ axis).angle((b_quaternion @ axis)) - (math.pi / 2)) < 1e-5:
-                    return True
-            return False
-
-        def get_camera_block(obj):
-            raster_x = obj.data.BIMCameraProperties.raster_x
-            raster_y = obj.data.BIMCameraProperties.raster_y
-
-            if raster_x > raster_y:
-                width = obj.data.ortho_scale
-                height = width / raster_x * raster_y
-            else:
-                height = obj.data.ortho_scale
-                width = height / raster_y * raster_x
-            depth = obj.data.clip_end
-
-            verts = (
-                obj.matrix_world @ mathutils.Vector((-width / 2, -height /2, -depth)),
-                obj.matrix_world @ mathutils.Vector((-width / 2, -height /2, 0)),
-                obj.matrix_world @ mathutils.Vector((-width / 2, height /2, -depth)),
-                obj.matrix_world @ mathutils.Vector((-width / 2, height /2, 0)),
-                obj.matrix_world @ mathutils.Vector((width / 2, -height /2, -depth)),
-                obj.matrix_world @ mathutils.Vector((width / 2, -height /2, 0)),
-                obj.matrix_world @ mathutils.Vector((width / 2, height /2, -depth)),
-                obj.matrix_world @ mathutils.Vector((width / 2, height /2, 0))
-            )
-            faces = [
-                [0, 1, 3, 2],
-                [2, 3, 7, 6],
-                [6, 7, 5, 4],
-                [4, 5, 1, 0],
-                [2, 6, 4, 0],
-                [7, 3, 1, 5],
-            ]
-            return {"verts": verts, "faces": faces}
-
-        def is_intersecting(a, b):
-            a_block = get_camera_block(a)
-            a_tree = mathutils.bvhtree.BVHTree.FromPolygons(a_block["verts"], a_block["faces"])
-            b_block = get_camera_block(b)
-            b_tree = mathutils.bvhtree.BVHTree.FromPolygons(b_block["verts"], b_block["faces"])
-            return bool(a_tree.overlap(b_tree))
+        bounds = helper.ortho_view_frame(camera.data) if camera.data.type == "ORTHO" else None
 
         def to_camera_coords(camera, reference_obj):
             mat = reference_obj.matrix_world.copy()
@@ -476,14 +431,90 @@ class Drawing(blenderbim.core.tool.Drawing):
             mat[0][3] = xyz[0]
             mat[1][3] = xyz[1]
             mat[2][3] = xyz[2]
-            annotation_offset = mathutils.Vector((0, 0, -camera.data.clip_start))
+            annotation_offset = mathutils.Vector((0, 0, -camera.data.clip_start - 0.05))
             annotation_offset = camera.matrix_world.to_quaternion() @ annotation_offset
             mat[0][3] += annotation_offset[0]
             mat[1][3] += annotation_offset[1]
             mat[2][3] += annotation_offset[2]
             return mat
 
-        if is_perpendicular(camera, reference_obj) and is_intersecting(camera, reference_obj):
+        def clip_to_camera_boundary(mesh, bounds):
+            mesh.verts.ensure_lookup_table()
+            points = [v.co for v in mesh.verts[0:2]]
+            points = helper.clip_segment(bounds, points)
+            if points is None:
+                return None
+            mesh.verts[0].co = points[0]
+            mesh.verts[1].co = points[1]
+            return mesh
+
+        if cls.is_perpendicular(camera, reference_obj) and cls.is_intersecting(camera, reference_obj):
+            reference_mesh = cls.get_camera_block(reference_obj)
+            obj_matrix = to_camera_coords(camera, reference_obj)
+
+            # The reference mesh vertices represent a view cube. To convert this into a section line we:
+            # 1. Select the 4 +Z vertices local to the reference element. This is the cutting plane.
+            verts_local_to_reference = [reference_obj.matrix_world.inverted() @ v for v in reference_mesh["verts"]]
+            cutting_plane_verts = sorted(verts_local_to_reference, key=lambda x: x.z)[-4:]
+            # Filter verts with the same XY coords
+            #set([v.xy for v in cutting_plane_verts])
+
+            global_cutting_plane_verts = [reference_obj.matrix_world @ v for v in cutting_plane_verts]
+            # 2. Project the cutting plane onto our viewing camera.
+            verts_local_to_camera = [camera.matrix_world.inverted() @ v for v in global_cutting_plane_verts]
+            # 3. Collapse verts with the same XY coords, and set Z to be just below the clip_start so it's visible
+            collapsed_verts = []
+            for vert in verts_local_to_camera:
+                if not [True for v in collapsed_verts if (vert.xy - v.xy).length < 1e-2]:
+                    collapsed_verts.append(mathutils.Vector((vert.x, vert.y, -camera.data.clip_start - 0.05)))
+            # 4. The first two vertices is the section line
+            section_line = collapsed_verts[0:2]
+            global_section_line = [camera.matrix_world @ v for v in section_line]
+            local_section_line = [obj_matrix.inverted() @ v for v in global_section_line]
+
+            mesh = bpy.data.meshes.new(name="Annotation")
+            mesh.from_pydata(local_section_line, [(0, 1)], [])
+            bm = bmesh.new()
+            bm.from_mesh(mesh)
+            bm = clip_to_camera_boundary(bm, bounds)
+            bm.to_mesh(mesh)
+            bm.free()
+
+            obj = bpy.data.objects.new(reference_obj.name, mesh)
+            obj.matrix_world = obj_matrix
+
+            element = cls.run_root_assign_class(
+                obj=obj,
+                ifc_class="IfcAnnotation",
+                predefined_type="SECTION",
+                should_add_representation=True,
+                context=context,
+                ifc_representation_class=None,
+            )
+            return element
+
+    @classmethod
+    def generate_elevation_reference_annotation(cls, drawing, reference_element, context):
+        reference_obj = tool.Ifc.get_object(reference_element)
+        reference_obj.matrix_world
+        camera = tool.Ifc.get_object(drawing)
+
+        def to_camera_coords(camera, reference_obj):
+            mat = reference_obj.matrix_world.copy()
+            xyz = camera.matrix_world.inverted() @ reference_obj.matrix_world.translation
+            xyz[2] = 0
+            xyz = camera.matrix_world @ xyz
+            mat[0][3] = xyz[0]
+            mat[1][3] = xyz[1]
+            mat[2][3] = xyz[2]
+            annotation_offset = mathutils.Vector((0, 0, -camera.data.clip_start - 0.05))
+            annotation_offset = camera.matrix_world.to_quaternion() @ annotation_offset
+            mat[0][3] += annotation_offset[0]
+            mat[1][3] += annotation_offset[1]
+            mat[2][3] += annotation_offset[2]
+            return mat
+
+        if cls.is_perpendicular(camera, reference_obj) and cls.is_intersecting(camera, reference_obj):
             obj = bpy.data.objects.new(reference_obj.name, None)
             obj.empty_display_size = 0.1
             obj.matrix_world = to_camera_coords(camera, reference_obj)
@@ -530,7 +561,7 @@ class Drawing(blenderbim.core.tool.Drawing):
         def to_camera_coords(obj, mesh):
             mesh.transform(camera.matrix_world.inverted() @ obj.matrix_world)
             obj.matrix_world = camera.matrix_world
-            annotation_offset = mathutils.Vector((0, 0, -camera.data.clip_start))
+            annotation_offset = mathutils.Vector((0, 0, -camera.data.clip_start - 0.05))
             annotation_offset = camera.matrix_world.to_quaternion() @ annotation_offset
             obj.matrix_world[0][3] += annotation_offset[0]
             obj.matrix_world[1][3] += annotation_offset[1]
@@ -585,6 +616,57 @@ class Drawing(blenderbim.core.tool.Drawing):
         )
         return element
 
+    @classmethod
+    def is_perpendicular(cls, a, b):
+        axes = [mathutils.Vector((1, 0, 0)), mathutils.Vector((0, 1, 0)), mathutils.Vector((0, 0, 1))]
+        a_quaternion = a.matrix_world.to_quaternion()
+        b_quaternion = b.matrix_world.to_quaternion()
+        for axis in axes:
+            if abs((a_quaternion @ axis).angle((b_quaternion @ axis)) - (math.pi / 2)) < 1e-5:
+                return True
+        return False
+
+    @classmethod
+    def get_camera_block(cls, obj):
+        raster_x = obj.data.BIMCameraProperties.raster_x
+        raster_y = obj.data.BIMCameraProperties.raster_y
+
+        if raster_x > raster_y:
+            width = obj.data.ortho_scale
+            height = width / raster_x * raster_y
+        else:
+            height = obj.data.ortho_scale
+            width = height / raster_y * raster_x
+        depth = obj.data.clip_end
+
+        verts = (
+            obj.matrix_world @ mathutils.Vector((-width / 2, -height /2, -depth)),
+            obj.matrix_world @ mathutils.Vector((-width / 2, -height /2, 0)),
+            obj.matrix_world @ mathutils.Vector((-width / 2, height /2, -depth)),
+            obj.matrix_world @ mathutils.Vector((-width / 2, height /2, 0)),
+            obj.matrix_world @ mathutils.Vector((width / 2, -height /2, -depth)),
+            obj.matrix_world @ mathutils.Vector((width / 2, -height /2, 0)),
+            obj.matrix_world @ mathutils.Vector((width / 2, height /2, -depth)),
+            obj.matrix_world @ mathutils.Vector((width / 2, height /2, 0))
+        )
+        faces = [
+            [0, 1, 3, 2],
+            [2, 3, 7, 6],
+            [6, 7, 5, 4],
+            [4, 5, 1, 0],
+            [2, 6, 4, 0],
+            [7, 3, 1, 5],
+        ]
+        return {"verts": verts, "faces": faces}
+
+    @classmethod
+    def is_intersecting(cls, a, b):
+        a_block = cls.get_camera_block(a)
+        a_tree = mathutils.bvhtree.BVHTree.FromPolygons(a_block["verts"], a_block["faces"])
+        b_block = cls.get_camera_block(b)
+        b_tree = mathutils.bvhtree.BVHTree.FromPolygons(b_block["verts"], b_block["faces"])
+        return bool(a_tree.overlap(b_tree))
+
     @classmethod
     def sync_object_representation(cls, obj):
         bpy.ops.bim.update_representation(obj=obj.name)