bonsai-impl-modeling

name	bonsai-impl-modeling
description	Use when placing building elements (walls, slabs, columns, beams) in Bonsai or assigning IFC types and materials. Prevents the common mistake of creating geometry without assigning it to the spatial hierarchy (orphaned elements). Covers the complete element creation pipeline: type selection, geometric representation, material layer/profile/constituent assignment, and spatial containment. Keywords: wall, slab, column, beam, IfcWall, IfcSlab, IFC type, predefined type, material layer, material profile, spatial assignment, BIM modeling, make a wall, create building elements, add floor.
license	MIT
compatibility	Designed for Claude Code. Requires Python 3.x.
metadata	{"author":"OpenAEC-Foundation","version":"1.0"}

Bonsai Implementation: BIM Modeling

Version: Bonsai v0.8.x | Blender 4.2.0+ | Python 3.11 Module path: bonsai.bim.module.model — NEVER blenderbim.* Data layer: All IFC operations use ifcopenshell.api.run()

1. Critical Warnings

1. ALWAYS use bonsai.* — NEVER blenderbim.*. The rename occurred in 2024 (v0.8.0).
2. ALWAYS check IfcStore.get_file() for None before any IFC operation.
3. ALWAYS verify representation context exists before creating geometry.
4. ALWAYS use spatial.assign_container for placing elements in storeys — NEVER aggregate.assign_object.
5. ALWAYS use feature.add_feature for openings — NEVER void.add_opening (does not exist in v0.8.0+).
6. ALWAYS pass lists to related_objects / products parameters — NEVER single entities.
7. ALWAYS call bpy.ops.bim.edit_object_placement() after moving Blender objects to sync IFC placement.
8. NEVER treat Bonsai as an importer/exporter — IFC IS the native document.

2. Element Creation Pipeline

Decision Tree: Which Workflow?

Need to create a building element?
├── Is there an existing IfcElementType for it?
│   ├── YES → Use Type-Based Workflow (§2.1)
│   └── NO  → Create type first (§3), then use Type-Based Workflow
│
├── Element category?
│   ├── Wall         → Layer-based type (IfcMaterialLayerSet)     → §4.1
│   ├── Slab/Plate   → Layer-based type (IfcMaterialLayerSet)     → §4.1
│   ├── Column/Beam  → Profile-based type (IfcMaterialProfileSet) → §4.2
│   ├── Door/Window   → Parametric type (mapped geometry)         → §4.3
│   └── Custom/Other → Constituent set or direct mesh             → §4.4

2.1 Type-Based Element Creation (Standard Workflow)

Every building element in Bonsai follows this pipeline:

Step 1: Get IFC model          → IfcStore.get_file()
Step 2: Ensure context exists  → ifcopenshell.util.representation.get_context()
Step 3: Get/create type        → root.create_entity(ifc_class="IfcWallType")
Step 4: Configure type material → material.add_material_set() + material.assign_material()
Step 5: Create occurrence      → root.create_entity(ifc_class="IfcWall")
Step 6: Assign type            → type.assign_type(related_objects=[wall], relating_type=wall_type)
Step 7: Create representation  → geometry.add_wall_representation() / add_profile_representation()
Step 8: Assign representation  → geometry.assign_representation()
Step 9: Place in spatial tree  → spatial.assign_container(products=[wall], relating_structure=storey)
Step 10: Set placement         → geometry.edit_object_placement()

2.2 Representation Context Setup

ALWAYS verify context exists before creating geometry:

import ifcopenshell.util.representation

body_context = ifcopenshell.util.representation.get_context(
    model, "Model", "Body", "MODEL_VIEW")

if not body_context:
    model_ctx = ifcopenshell.api.run("context.add_context", model,
        context_type="Model")
    body_context = ifcopenshell.api.run("context.add_context", model,
        context_type="Model",
        context_identifier="Body",
        target_view="MODEL_VIEW",
        parent=model_ctx)

3. Type System

3.1 Creating Element Types

wall_type = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcWallType",
    predefined_type="STANDARD",
    name="200mm Concrete Wall")

3.2 Type-to-Representation Template Mapping

IFC Type Class	Material Set Type	Representation Template
IfcWallType	IfcMaterialLayerSet	LAYERSET_AXIS2
IfcSlabType	IfcMaterialLayerSet	LAYERSET_AXIS3
IfcPlateType	IfcMaterialLayerSet	LAYERSET_AXIS3
IfcColumnType	IfcMaterialProfileSet	PROFILESET
IfcBeamType	IfcMaterialProfileSet	PROFILESET
IfcMemberType	IfcMaterialProfileSet	PROFILESET
IfcFootingType	IfcMaterialProfileSet	PROFILESET
IfcDoorType	Direct/Constituent	DOOR
IfcWindowType	Direct/Constituent	WINDOW
IfcFurnitureType	Direct/Constituent	MESH

3.3 Predefined Type Enums

IfcWallTypeEnum

STANDARD, SOLIDWALL, PARTITIONING, RETAININGWALL, SHEAR, PARAPET, USERDEFINED, NOTDEFINED

IfcSlabTypeEnum

FLOOR, ROOF, LANDING, BASESLAB, USERDEFINED, NOTDEFINED

IfcColumnTypeEnum

COLUMN, PILASTER, USERDEFINED, NOTDEFINED

IfcBeamTypeEnum

BEAM, JOIST, HOLLOWCORE, LINTEL, SPANDREL, T_BEAM, USERDEFINED, NOTDEFINED

3.4 Type Assignment

# Assign type to one or more occurrences
ifcopenshell.api.run("type.assign_type", model,
    related_objects=[wall1, wall2],   # ALWAYS a list
    relating_type=wall_type,
    should_map_representations=True)  # Inherits geometry via MappedItem

# Query type of an element
import ifcopenshell.util.element
element_type = ifcopenshell.util.element.get_type(wall1)

# Get all occurrences of a type
occurrences = ifcopenshell.util.element.get_types(wall_type)

3.5 MappedItem Geometry Sharing

When should_map_representations=True:

• Geometry is stored ONCE on the type's IfcRepresentationMap
• Each occurrence references it via IfcMappedItem with a per-instance transformation
• Editing the type geometry updates ALL occurrences automatically

4. Material Assignment

4.1 Material Layer Sets (Walls, Slabs, Plates)

# Step 1: Create materials
concrete = ifcopenshell.api.run("material.add_material", model,
    name="Concrete C25", category="concrete")
insulation = ifcopenshell.api.run("material.add_material", model,
    name="Mineral Wool", category="ite")

# Step 2: Create layer set
layer_set = ifcopenshell.api.run("material.add_material_set", model,
    name="200mm Insulated Wall", set_type="IfcMaterialLayerSet")

# Step 3: Add layers with thickness
layer_c = ifcopenshell.api.run("material.add_layer", model,
    layer_set=layer_set, material=concrete)
ifcopenshell.api.run("material.edit_layer", model,
    layer=layer_c, attributes={"LayerThickness": 0.150})

layer_i = ifcopenshell.api.run("material.add_layer", model,
    layer_set=layer_set, material=insulation)
ifcopenshell.api.run("material.edit_layer", model,
    layer=layer_i, attributes={"LayerThickness": 0.050})

# Step 4: Assign to type (NEVER to occurrence directly)
ifcopenshell.api.run("material.assign_material", model,
    products=[wall_type], material=layer_set)

4.2 Material Profile Sets (Columns, Beams)

# Step 1: Create material
steel = ifcopenshell.api.run("material.add_material", model,
    name="S355 Steel", category="steel")

# Step 2: Create profile definition
profile = model.create_entity("IfcIShapeProfileDef",
    ProfileType="AREA", ProfileName="HEA200",
    OverallWidth=0.200, OverallDepth=0.190,
    WebThickness=0.0065, FlangeThickness=0.010)

# Step 3: Create profile set and add profile
profile_set = ifcopenshell.api.run("material.add_material_set", model,
    name="HEA 200 Steel", set_type="IfcMaterialProfileSet")
ifcopenshell.api.run("material.add_profile", model,
    profile_set=profile_set, material=steel, profile=profile)

# Step 4: Assign to type
ifcopenshell.api.run("material.assign_material", model,
    products=[column_type], material=profile_set)

4.3 Material Constituent Sets (Doors, Windows, Custom)

constituent_set = ifcopenshell.api.run("material.add_material_set", model,
    name="Door Materials", set_type="IfcMaterialConstituentSet")

wood = ifcopenshell.api.run("material.add_material", model,
    name="Oak", category="wood")
glass = ifcopenshell.api.run("material.add_material", model,
    name="Float Glass", category="glass")

ifcopenshell.api.run("material.add_constituent", model,
    constituent_set=constituent_set, material=wood, name="Frame")
ifcopenshell.api.run("material.add_constituent", model,
    constituent_set=constituent_set, material=glass, name="Glazing")

ifcopenshell.api.run("material.assign_material", model,
    products=[door_type], material=constituent_set)

4.4 Material Assignment Decision Tree

What element type?
├── Wall / Slab / Plate → IfcMaterialLayerSet      → assign to TYPE
├── Column / Beam       → IfcMaterialProfileSet     → assign to TYPE
├── Door / Window       → IfcMaterialConstituentSet  → assign to TYPE
├── Generic element     → IfcMaterial (single)       → assign to TYPE or occurrence
└── Composite           → IfcMaterialConstituentSet  → assign to TYPE

Rule: ALWAYS assign materials to the TYPE, not to individual occurrences. Occurrences inherit materials from their type via IfcMaterialLayerSetUsage or IfcMaterialProfileSetUsage.

5. Geometry Creation

5.1 Wall Geometry

representation = ifcopenshell.api.run(
    "geometry.add_wall_representation", model,
    context=body_context,
    length=5.0,       # meters
    height=3.0,       # meters
    thickness=0.2,    # meters
    offset=0.0,
    x_angle=0.0)      # radians, for sloped walls

ifcopenshell.api.run("geometry.assign_representation", model,
    product=wall, representation=representation)

5.2 Slab Geometry

representation = ifcopenshell.api.run(
    "geometry.add_slab_representation", model,
    context=body_context,
    depth=0.2,
    polyline=[(0.0, 0.0), (10.0, 0.0), (10.0, 8.0), (0.0, 8.0)])

ifcopenshell.api.run("geometry.assign_representation", model,
    product=slab, representation=representation)

5.3 Profile-Based Geometry (Columns, Beams)

representation = ifcopenshell.api.run(
    "geometry.add_profile_representation", model,
    context=body_context,
    profile=profile_def,    # IfcProfileDef entity
    depth=3.0,              # extrusion length
    cardinal_point=5)       # mid-depth centre

ifcopenshell.api.run("geometry.assign_representation", model,
    product=column, representation=representation)

Cardinal Point Reference

Value	Position
1	Bottom left
2	Bottom centre
3	Bottom right
4	Mid-depth left
5	Mid-depth centre
6	Mid-depth right
7	Top left
8	Top centre
9	Top right
10	Geometric centroid

5.4 Common Profile Definitions

# Rectangle (columns, beams)
rect_profile = model.create_entity("IfcRectangleProfileDef",
    ProfileType="AREA", ProfileName="400x400",
    XDim=0.4, YDim=0.4)

# I-Shape (steel beams/columns)
i_profile = model.create_entity("IfcIShapeProfileDef",
    ProfileType="AREA", ProfileName="HEA200",
    OverallWidth=0.200, OverallDepth=0.190,
    WebThickness=0.0065, FlangeThickness=0.010)

# Circle (pipes, round columns)
circle_profile = model.create_entity("IfcCircleProfileDef",
    ProfileType="AREA", ProfileName="D300",
    Radius=0.15)

# Or use the API for parameterized profiles
profile = ifcopenshell.api.run("profile.add_parameterized_profile", model,
    ifc_class="IfcRectangleProfileDef")

6. Element Placement

6.1 Setting Object Placement

import numpy as np

matrix = np.array([
    [1.0, 0.0, 0.0, 5.0],   # X translation = 5m
    [0.0, 1.0, 0.0, 0.0],   # Y translation = 0m
    [0.0, 0.0, 1.0, 3.0],   # Z translation = 3m (e.g., storey offset)
    [0.0, 0.0, 0.0, 1.0]
], dtype=float)

ifcopenshell.api.run("geometry.edit_object_placement", model,
    product=wall, matrix=matrix, is_si=True)

6.2 Spatial Container Assignment

storey = model.by_type("IfcBuildingStorey")[0]

ifcopenshell.api.run("spatial.assign_container", model,
    products=[wall, column, slab],   # ALWAYS a list
    relating_structure=storey)

7. Opening and Void Operations

# Step 1: Create the opening element
opening = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcOpeningElement", name="Opening-001")

# Step 2: Create opening geometry
opening_repr = ifcopenshell.api.run(
    "geometry.add_wall_representation", model,
    context=body_context,
    length=1.0, height=2.1, thickness=0.25)

ifcopenshell.api.run("geometry.assign_representation", model,
    product=opening, representation=opening_repr)

# Step 3: Add opening to host wall (creates IfcRelVoidsElement)
ifcopenshell.api.run("feature.add_feature", model,
    feature=opening, element=wall)

# Step 4: Fill with door (creates IfcRelFillsElement)
ifcopenshell.api.run("void.add_filling", model,
    opening=opening, element=door)

8. Parametric Arrays (Bonsai-Specific)

Bonsai uses BBIM_Array property set for parametric element arrays:

# Array data structure stored in EPset_Parametric
array_data = {
    "children": [],          # GlobalIds of child copies
    "count": 5,              # Number of copies
    "x": 3.0,               # X offset between copies (meters)
    "y": 0.0,               # Y offset
    "z": 0.0,               # Z offset
    "use_local_space": True, # Offset relative to element's local axes
    "method": "OFFSET"       # Offset method
}

9. Bonsai Operator Quick Reference

Operator	Purpose
bpy.ops.bim.assign_class()	Assign IFC class to Blender object
bpy.ops.bim.edit_object_placement()	Sync Blender transform to IFC
bpy.ops.bim.save_project()	Save IFC file
bpy.ops.bim.add_type_instance()	Place instance of existing type

Rule: ALWAYS prefer ifcopenshell.api.run() over bpy.ops.bim.* in scripts — the API is more stable and explicit.

10. Reference Links

• API Signatures: See references/methods.md
• Complete Code Examples: See references/examples.md
• Anti-Patterns: See references/anti-patterns.md