Bonsai Spatial Structure Syntax

Version: Bonsai v0.8.x | Blender 4.2.0+ | Python 3.11 Module path: bonsai.* — NEVER blenderbim.* Source files: core/spatial.py, tool/spatial.py, bim/module/spatial/

Critical Warnings

1. ALWAYS use bonsai.* imports. NEVER use blenderbim.* — renamed in 2024 (v0.8.0+).
2. ALWAYS build spatial hierarchy via IfcRelAggregates using ifcopenshell.api.run("aggregate.assign_object", ...). NEVER create spatial elements without connecting them to the hierarchy.
3. ALWAYS use ifcopenshell.api.run("spatial.assign_container", ...) to place physical elements in spatial containers. NEVER set containment via direct attribute manipulation.
4. ALWAYS pass products as a list (v0.8+ breaking change): products=[wall], NOT product=wall.
5. NEVER delete IfcProject — it is the root of every IFC model. Bonsai operators enforce this constraint.
6. ALWAYS set a default container (typically IfcBuildingStorey) before creating elements. Use bpy.ops.bim.set_default_container(container=storey_id).
7. NEVER assign an element to multiple containers via IfcRelContainedInSpatialStructure — an element can only be contained in ONE spatial structure. Use IfcRelReferencedInSpatialStructure for multi-storey references.
8. ALWAYS use ifcopenshell.api.run("root.create_entity", ...) to create spatial elements. NEVER use model.create_entity() — it skips GlobalId generation and ownership assignment.

IFC Spatial Hierarchy

IfcProject                          (exactly 1 per file, root node)
  └── IfcSite                       (via IfcRelAggregates)
        └── IfcBuilding             (via IfcRelAggregates)
              └── IfcBuildingStorey  (via IfcRelAggregates)
                    ├── IfcSpace    (via IfcRelAggregates)
                    ├── IfcWall     (via IfcRelContainedInSpatialStructure)
                    ├── IfcDoor     (via IfcRelContainedInSpatialStructure)
                    └── IfcColumn   (via IfcRelContainedInSpatialStructure)

Spatial Elements

IFC Class	Purpose	Required?	Typical Count
IfcProject	Root of model	YES (exactly 1)	1
IfcSite	Geographic land parcel	Recommended	1+
IfcBuilding	Physical building structure	Recommended	1+
IfcBuildingStorey	Floor level	Recommended	1+ per building
IfcSpace	Room, corridor, void	Optional	0+ per storey

Three Key Relationships

Relationship	IFC Class	Purpose	Cardinality
Spatial decomposition	IfcRelAggregates	Parent-child between spatial elements	1:N
Spatial containment	IfcRelContainedInSpatialStructure	Places physical elements in a spatial zone	1:N (exclusive)
Spatial reference	IfcRelReferencedInSpatialStructure	Non-exclusive reference (multi-storey elements)	M:N

Decision Tree: Spatial Operations

What spatial operation do you need?
│
├── Create spatial hierarchy (Project/Site/Building/Storey)?
│   ├── Create elements: root.create_entity with ifc_class="IfcSite" etc.
│   └── Connect hierarchy: aggregate.assign_object
│
├── Place physical element (wall/door/column) in a storey or space?
│   └── spatial.assign_container (products=[element], relating_structure=storey)
│
├── Remove element from container?
│   └── spatial.unassign_container (products=[element])
│
├── Reference element in additional storey (multi-storey column)?
│   └── spatial.reference_structure (products=[element], relating_structure=storey2)
│
├── Remove spatial reference?
│   └── spatial.dereference_structure (products=[element], relating_structure=storey2)
│
├── Query spatial containment?
│   └── ifcopenshell.util.element.get_container(element)
│
├── Query spatial decomposition?
│   └── ifcopenshell.util.element.get_decomposition(container)
│
├── Delete spatial container?
│   └── bpy.ops.bim.delete_container(container=container_id)
│   NOTE: Cannot delete IfcProject
│
└── Generate IfcSpace from walls?
    ├── From cursor/object position: bpy.ops.bim.generate_space()
    └── From selected walls: bpy.ops.bim.generate_spaces_from_walls()

Essential Patterns

Pattern 1: Build Complete Spatial Hierarchy

# Bonsai v0.8.x — Build spatial hierarchy from scratch
# Requires: active Bonsai project in Blender
import bpy
import ifcopenshell
import ifcopenshell.api

model = ifcopenshell.file(schema="IFC4")

# Step 1: Create project (root)
project = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcProject", name="My Project")

# Step 2: Assign units (required before geometry)
ifcopenshell.api.run("unit.assign_unit", model)

# Step 3: Create spatial elements
site = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcSite", name="Default Site")
building = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcBuilding", name="Building A")
ground_floor = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcBuildingStorey", name="Ground Floor")
first_floor = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcBuildingStorey", name="First Floor")

# Step 4: Connect hierarchy via IfcRelAggregates
ifcopenshell.api.run("aggregate.assign_object", model,
    products=[site], relating_object=project)
ifcopenshell.api.run("aggregate.assign_object", model,
    products=[building], relating_object=site)
ifcopenshell.api.run("aggregate.assign_object", model,
    products=[ground_floor, first_floor], relating_object=building)

Pattern 2: Assign Element to Container

# Bonsai v0.8.x — Place wall in a storey
wall = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcWall", name="Wall 001")

# Assign to ground floor (IfcRelContainedInSpatialStructure)
ifcopenshell.api.run("spatial.assign_container", model,
    products=[wall], relating_structure=ground_floor)

Pattern 3: Multi-Storey Element Reference

# Bonsai v0.8.x — Column spanning two storeys
column = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcColumn", name="Column C1")

# Primary containment in ground floor
ifcopenshell.api.run("spatial.assign_container", model,
    products=[column], relating_structure=ground_floor)

# Additional reference in first floor (IfcRelReferencedInSpatialStructure)
ifcopenshell.api.run("spatial.reference_structure", model,
    products=[column], relating_structure=first_floor)

Pattern 4: Query Spatial Information

# Bonsai v0.8.x — Query spatial relationships
import ifcopenshell.util.element

# Get container of an element
container = ifcopenshell.util.element.get_container(wall)
# Returns: IfcBuildingStorey or None

# Get all elements in a container
elements = ifcopenshell.util.element.get_decomposition(building)
# Returns: list of child spatial elements

# Get all parts (direct children via IfcRelAggregates)
parts = ifcopenshell.util.element.get_parts(building)
# Returns: list of IfcBuildingStorey instances

Pattern 5: Bonsai Operators for Spatial Operations

# Bonsai v0.8.x — Using Bonsai operators (inside Blender)
import bpy

# Set default container for new elements
bpy.ops.bim.set_default_container(container=storey.id())

# Assign selected objects to a container
bpy.ops.bim.assign_container(container=storey.id())

# Remove container assignment from selected objects
bpy.ops.bim.remove_container()

# Reference selected objects from a structure
bpy.ops.bim.reference_structure()

# Delete a spatial container (NOT IfcProject)
bpy.ops.bim.delete_container(container=storey.id())

# Copy selected objects to another container
bpy.ops.bim.copy_to_container(container=target_storey.id())

# Generate IfcSpace from surrounding walls
bpy.ops.bim.generate_space()

# Generate spaces from selected walls
bpy.ops.bim.generate_spaces_from_walls()

# Load spatial decomposition tree in UI
bpy.ops.bim.import_spatial_decomposition()

# Select all objects in a container
bpy.ops.bim.select_similar_container(is_recursive=True)

# Toggle IfcSpace visibility
bpy.ops.bim.toggle_spatial_elements(is_visible=True)

Bonsai Three-Layer Architecture (Spatial Module)

DELIVERY LAYER — bim/module/spatial/operator.py
  BIM_OT_assign_container, BIM_OT_delete_container, etc.
  Calls: core.spatial.assign_container(tool.Ifc, tool.Spatial, ...)
  ─────────────────────────────────────────────────────────
DOMAIN LAYER — core/spatial.py
  assign_container(), reference_structure(), generate_space(), etc.
  Validates via: spatial.can_contain(), spatial.can_reference()
  Calls: ifc.run("spatial.assign_container", ...)
  ─────────────────────────────────────────────────────────
TOOL LAYER — tool/spatial.py
  Spatial.get_container(), Spatial.can_contain(), etc.
  Concrete implementation using bpy + ifcopenshell

Operator Execution Pattern

# bim/module/spatial/operator.py (Delivery Layer)
class BIM_OT_assign_container(bpy.types.Operator):
    bl_idname = "bim.assign_container"
    bl_label = "Assign Container"
    bl_options = {"REGISTER", "UNDO"}
    container: bpy.props.IntProperty()

    def execute(self, context):
        return IfcStore.execute_ifc_operator(self, context)

    def _execute(self, context):
        # Dependency injection: pass tool implementations to core
        core.spatial.assign_container(
            tool.Ifc, tool.Collector, tool.Spatial,
            container=tool.Ifc.get().by_id(self.container),
            objs=context.selected_objects,
        )
        return {"FINISHED"}

Key Rules

1. Operators call IfcStore.execute_ifc_operator(self, context) — wraps IFC ops with undo.
2. Actual logic goes in _execute(), NOT execute().
3. Tool classes (tool.Ifc, tool.Spatial) are passed as dependency injection.
4. bl_options ALWAYS includes "UNDO" for IFC-modifying operators.

Spatial Validation Rules

Containment Validation (can_contain)

An element can be contained in a spatial structure element ONLY if:

1. The container is an IfcSpatialStructureElement (IFC2X3) or also IfcExternalSpatialStructureElement (IFC4+)
2. The element has a ContainedInStructure inverse attribute

Reference Validation (can_reference)

An element can reference a spatial structure ONLY if:

1. The structure is an IfcSpatialStructureElement (IFC2X3) or IfcSpatialElement (IFC4+)
2. The element has a ReferencedInStructures inverse attribute

Default Project Structure

When creating a new IFC project via Bonsai UI (File > New IFC Project), Bonsai generates:

IfcProject  "My Project"
  └── IfcSite  "My Site"
        └── IfcBuilding  "My Building"
              └── IfcBuildingStorey  "My Storey"  (Elevation: 0.0)

The default container is set to IfcBuildingStorey "My Storey".

Space Generation

Bonsai provides two automated space generation methods:

From Context (Surrounding Walls)

1. Set default container (an IfcBuildingStorey)
2. Position cursor or select an object at the space location
3. Call bpy.ops.bim.generate_space()
4. Bonsai bisects visible walls/columns at storey elevation, polygonizes boundaries, finds the enclosing polygon, and extrudes it to create an IfcSpace

From Selected Walls

1. Select wall objects that enclose spaces
2. Call bpy.ops.bim.generate_spaces_from_walls()
3. Bonsai computes the union of wall footprints and creates IfcSpace elements from interior holes

IFC Schema Version Differences

Entity / Feature	IFC2X3	IFC4	IFC4X3
IfcSite	Yes	Yes	Yes
IfcBuilding	Yes	Yes	Yes
IfcBuildingStorey	Yes	Yes	Yes
IfcSpace	Yes	Yes	Yes
IfcFacility	No	No	Yes
IfcFacilityPart	No	No	Yes
IfcSpatialElement (base class)	No	Yes	Yes
IfcExternalSpatialStructureElement	No	Yes	Yes
Containment validation class	IfcSpatialStructureElement	+ IfcExternalSpatialStructureElement	+ IfcExternalSpatialStructureElement
Reference validation class	IfcSpatialStructureElement	IfcSpatialElement	IfcSpatialElement

Source Code Paths

Component	Path in IfcOpenShell Monorepo
Core logic	src/bonsai/bonsai/core/spatial.py
Tool implementation	src/bonsai/bonsai/tool/spatial.py
Operators	src/bonsai/bonsai/bim/module/spatial/operator.py
UI panels	src/bonsai/bonsai/bim/module/spatial/ui.py
Properties	src/bonsai/bonsai/bim/module/spatial/prop.py
Interface contract	src/bonsai/bonsai/core/tool.py (class Spatial)

Dependencies

• ifcos-syntax-api — For ifcopenshell.api.run() invocation patterns and module reference
• bonsai-core-architecture — For three-layer architecture, IfcStore, tool.Ifc patterns

Reference Links

• Spatial API Method Signatures — Complete signatures for core, tool, and operator methods
• Working Code Examples — End-to-end spatial structure examples
• Anti-Patterns — Common spatial structure mistakes and how to avoid them