Bonsai Impl Project

Bonsai Project Management

Version: Bonsai v0.8.x | IfcOpenShell v0.8.x | IFC2X3 / IFC4 / IFC4X3 Dependency: bonsai-core-architecture (MUST read first) Module path: bonsai.* — NEVER blenderbim.*

Critical Warnings

1. ALWAYS use ifcopenshell.api.project.create_file() to create new IFC projects. NEVER use ifcopenshell.file() directly — it skips required project setup (IfcProject, IfcUnitAssignment, representation contexts).
2. ALWAYS set units via ifcopenshell.api.unit.assign_unit() immediately after project creation. An IFC file without a unit assignment is invalid per all IFC schemas.
3. NEVER describe the Bonsai workflow as "import/export". The IFC file IS the native document.
4. ALWAYS use bonsai.* imports. NEVER use blenderbim.* — renamed in 2024 (v0.8.0+).
5. ALWAYS check IfcStore.get_file() for None before any IFC operation.
6. ALWAYS call ifcopenshell.api.georeference.add_georeferencing() before edit_georeferencing(). Editing non-existent entities raises an error.
7. NEVER set Eastings/Northings without confirmed survey data. Wrong values place the building at the wrong location on Earth.
8. ALWAYS run scripts via blender --python. NEVER import bonsai.* from system Python.

Schema Selection Decision Tree

Which IFC schema should I use?
|
+--> Legacy project or government mandate for IFC2X3?
|    +--> YES --> schema="IFC2X3"
|    +--> NO  --> Continue
|
+--> Infrastructure project (roads, bridges, tunnels, rail)?
|    +--> YES --> schema="IFC4X3"
|    +--> NO  --> Continue
|
+--> Default for buildings
     +--> schema="IFC4"

Project Creation

Decision Tree: How to Create a Project

Creating an IFC project?
|
+--> Inside Blender with Bonsai?
|    |
|    +--> Quick start?
|    |    +--> bpy.ops.bim.create_project(template="metric_m")
|    |
|    +--> Custom setup?
|         +--> bpy.ops.bim.create_project() with wizard options
|
+--> Standalone Python (no Blender)?
     |
     +--> model = ifcopenshell.api.project.create_file(version="IFC4")
     +--> ifcopenshell.api.unit.assign_unit(model)
     +--> Create IfcSite, IfcBuilding, IfcStorey
     +--> model.write("project.ifc")

Standalone Project Creation (No Blender)

import ifcopenshell
import ifcopenshell.api

# Step 1: Create file with schema selection
model = ifcopenshell.api.project.create_file(version="IFC4")

# Step 2: Assign units (metric, millimeters for length)
ifcopenshell.api.unit.assign_unit(model,
    length={"is_metric": True, "raw": "MILLIMETRE"},
    area={"is_metric": True, "raw": "SQUARE_METRE"},
    volume={"is_metric": True, "raw": "CUBIC_METRE"})

# Step 3: Create spatial hierarchy
project = model.by_type("IfcProject")[0]  # auto-created by create_file
site = ifcopenshell.api.root.create_entity(model,
    ifc_class="IfcSite", name="Default Site")
building = ifcopenshell.api.root.create_entity(model,
    ifc_class="IfcBuilding", name="Default Building")
storey = ifcopenshell.api.root.create_entity(model,
    ifc_class="IfcBuildingStorey", name="Ground Floor")

# Step 4: Create spatial containment hierarchy
ifcopenshell.api.aggregate.assign_object(model,
    relating_object=project, products=[site])
ifcopenshell.api.aggregate.assign_object(model,
    relating_object=site, products=[building])
ifcopenshell.api.aggregate.assign_object(model,
    relating_object=building, products=[storey])

# Step 5: Create representation contexts
model_context = ifcopenshell.api.context.add_context(model,
    context_type="Model")
body_context = ifcopenshell.api.context.add_context(model,
    context_type="Model",
    context_identifier="Body",
    target_view="MODEL_VIEW",
    parent=model_context)
plan_context = ifcopenshell.api.context.add_context(model,
    context_type="Plan")

# Step 6: Save
model.write("project.ifc")

Bonsai Project Creation (Inside Blender)

import bpy

# Method 1: Quick metric project (meters)
bpy.ops.bim.create_project(template="metric_m")

# Method 2: Quick metric project (millimeters)
bpy.ops.bim.create_project(template="metric_mm")

# Method 3: Quick imperial project (feet)
bpy.ops.bim.create_project(template="imperial_ft")

# Method 4: Demo project (pre-populated with example content)
bpy.ops.bim.create_project(template="demo")

Opening and Saving IFC Files

Decision Tree: File Operations

IFC file operation needed?
|
+--> Open existing file?
|    |
|    +--> Inside Blender?
|    |    +--> bpy.ops.bim.load_project(filepath="project.ifc")
|    |
|    +--> Standalone Python?
|         +--> model = ifcopenshell.open("project.ifc")
|
+--> Save project?
|    |
|    +--> Inside Blender?
|    |    +--> bpy.ops.bim.save_project(filepath="project.ifc")
|    |
|    +--> Standalone Python?
|         +--> model.write("project.ifc")
|
+--> Save to different file (Save As)?
     +--> model.write("new_path.ifc")

Standalone File I/O

import ifcopenshell

# Open
model = ifcopenshell.open("/path/to/project.ifc")

# Inspect
print(f"Schema: {model.schema}")        # "IFC2X3", "IFC4", "IFC4X3"
print(f"Project: {model.by_type('IfcProject')[0].Name}")

# Save (overwrites)
model.write("/path/to/project.ifc")

# Save As (new file)
model.write("/path/to/project_v2.ifc")

Bonsai File I/O (Inside Blender)

import bpy
from bonsai.bim.ifc import IfcStore

# Open
bpy.ops.bim.load_project(filepath="/path/to/project.ifc")

# Access the live IFC model
model = IfcStore.get_file()
if model is None:
    raise RuntimeError("No IFC project loaded")

# Save to current path
bpy.ops.bim.save_project()

# Save As
bpy.ops.bim.save_project(filepath="/path/to/project_v2.ifc")

Unit Configuration

Decision Tree: Unit Selection

What unit system?
|
+--> Metric (international)?
|    |
|    +--> Architecture/interiors (mm precision)?
|    |    +--> length: MILLIMETRE
|    |
|    +--> Urban/site planning (m precision)?
|         +--> length: METRE (or no prefix = default SI)
|
+--> Imperial (US/UK)?
     |
     +--> length: "foot" via add_conversion_based_unit
     +--> OR: "inch" for detail work

Unit Assignment Patterns

import ifcopenshell
import ifcopenshell.api

model = ifcopenshell.api.project.create_file(version="IFC4")

# Pattern 1: Default units (mm length, m² area, m³ volume)
ifcopenshell.api.unit.assign_unit(model)

# Pattern 2: Explicit metric (meters)
length_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="LENGTHUNIT", prefix=None)  # No prefix = metres
area_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="AREAUNIT", prefix=None)
volume_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="VOLUMEUNIT", prefix=None)
ifcopenshell.api.unit.assign_unit(model,
    units=[length_unit, area_unit, volume_unit])

# Pattern 3: Explicit metric (millimeters)
length_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="LENGTHUNIT", prefix="MILLI")
area_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="AREAUNIT", prefix=None)
volume_unit = ifcopenshell.api.unit.add_si_unit(model,
    unit_type="VOLUMEUNIT", prefix=None)
ifcopenshell.api.unit.assign_unit(model,
    units=[length_unit, area_unit, volume_unit])

# Pattern 4: Imperial (feet)
length_unit = ifcopenshell.api.unit.add_conversion_based_unit(model,
    name="foot")
area_unit = ifcopenshell.api.unit.add_conversion_based_unit(model,
    name="square foot")
ifcopenshell.api.unit.assign_unit(model,
    units=[length_unit, area_unit])

# Pattern 5: Add monetary unit
currency = ifcopenshell.api.unit.add_monetary_unit(model,
    currency="EUR")
ifcopenshell.api.unit.assign_unit(model, units=[currency])

SI Unit Prefixes

Conversion-Based Unit Names

Georeferencing

Decision Tree: Georeferencing Setup

Does the project need georeferencing?
|
+--> No survey data available?
|    +--> Skip georeferencing — add later when data is available
|
+--> Survey data available?
     |
     +--> Step 1: add_georeferencing()
     +--> Step 2: edit_georeferencing() with EPSG code + Eastings/Northings
     +--> Step 3 (optional): edit_true_north() for solar analysis

Georeferencing Setup Pattern

import ifcopenshell
import ifcopenshell.api
from math import cos, sin, radians

model = ifcopenshell.api.project.create_file(version="IFC4")

# Step 1: Initialize georeferencing entities
ifcopenshell.api.georeference.add_georeferencing(model)

# Step 2: Configure CRS and map conversion
ifcopenshell.api.georeference.edit_georeferencing(model,
    projected_crs={
        "Name": "EPSG:28992"  # Amersfoort / RD New (Netherlands)
    },
    coordinate_operation={
        "Eastings": 155000.0,
        "Northings": 463000.0,
        "OrthogonalHeight": 0.0,
        "XAxisAbscissa": cos(radians(0.0)),
        "XAxisOrdinate": sin(radians(0.0)),
        "Scale": 1.0
    })

# Step 3 (optional): Set true north for solar analysis
ifcopenshell.api.georeference.edit_true_north(model,
    true_north=5.0)  # Degrees anticlockwise from Y-axis

Common EPSG Codes for Construction

IFC2X3 Georeferencing (Legacy)

IFC2X3 does NOT have IfcMapConversion or IfcProjectedCRS entities. Instead, georeferencing uses the ePSet_MapConversion property set on IfcProject. The add_georeferencing API handles this automatically — use the same API calls regardless of schema version.

Header Metadata

import ifcopenshell
import ifcopenshell.api

model = ifcopenshell.open("project.ifc")

# Edit file header metadata
ifcopenshell.api.project.edit_header(model,
    editor="Jane Architect",
    organization="ACME Architecture",
    application="Bonsai v0.8.4",
    application_version="0.8.4")

model.write("project.ifc")

Owner History Setup

import ifcopenshell
import ifcopenshell.api

model = ifcopenshell.api.project.create_file(version="IFC4")

# Create person + organization (IFC4: optional but recommended)
person = ifcopenshell.api.owner.add_person(model,
    identification="jdoe",
    family_name="Doe",
    given_name="Jane")
org = ifcopenshell.api.owner.add_organisation(model,
    identification="ACME",
    name="ACME Architecture")
person_org = ifcopenshell.api.owner.add_person_and_organisation(model,
    person=person, organisation=org)

# Register application
app = ifcopenshell.api.owner.add_application(model,
    application_full_name="My BIM Tool",
    application_identifier="MyBIMTool",
    version="1.0")

# Configure automatic owner history for new entities
ifcopenshell.api.owner.settings.get_user = lambda ifc: person_org
ifcopenshell.api.owner.settings.get_application = lambda ifc: app

Schema Migration

import ifcopenshell
import ifcopenshell.util.schema

model_2x3 = ifcopenshell.open("legacy.ifc")
migrator = ifcopenshell.util.schema.Migrator()
model_ifc4 = migrator.migrate(model_2x3, "IFC4")
model_ifc4.write("migrated.ifc")

ALWAYS validate the migrated file with IfcTester after migration.

Representation Context Setup

Every IFC project MUST have at least one IfcGeometricRepresentationContext before any geometry can be assigned.

# Minimum required: Model context + Body sub-context
model_context = ifcopenshell.api.context.add_context(model,
    context_type="Model")
body_context = ifcopenshell.api.context.add_context(model,
    context_type="Model",
    context_identifier="Body",
    target_view="MODEL_VIEW",
    parent=model_context)

# Optional: Plan context for 2D views
plan_context = ifcopenshell.api.context.add_context(model,
    context_type="Plan")
annotation_context = ifcopenshell.api.context.add_context(model,
    context_type="Plan",
    context_identifier="Annotation",
    target_view="PLAN_VIEW",
    parent=plan_context)

Context Identifiers Reference

Project Lifecycle Summary

1. CREATE  --> ifcopenshell.api.project.create_file(version="IFC4")
2. UNITS   --> ifcopenshell.api.unit.assign_unit(model)
3. SPATIAL --> Create IfcSite, IfcBuilding, IfcBuildingStorey
4. CONTEXT --> ifcopenshell.api.context.add_context(model, ...)
5. GEO     --> ifcopenshell.api.georeference.add_georeferencing(model)
6. OWNER   --> ifcopenshell.api.owner.add_person/organisation(model)
7. MODEL   --> Add elements, properties, geometry
8. SAVE    --> model.write("project.ifc")

ALWAYS follow this order. Steps 5 and 6 are optional but recommended for production deliverables.

References

• methods.md — Complete API signatures for project, unit, georeference, context, owner modules
• examples.md — Working code examples for project lifecycle workflows
• anti-patterns.md — What NOT to do in project management

Sources

• Bonsai Documentation: https://docs.bonsaibim.org
• IfcOpenShell API: https://docs.ifcopenshell.org
• IfcOpenShell GitHub: https://github.com/IfcOpenShell/IfcOpenShell
• Bonsai source: src/bonsai/bonsai/bim/module/project/