bonsai-impl-project

name	bonsai-impl-project
description	Use when creating, opening, or configuring Bonsai IFC projects -- schema selection (IFC2X3/IFC4/IFC4X3), unit configuration, georeference setup, or project templates. Prevents the common mistake of not setting units before creating geometry (defaulting to incorrect units). Covers the complete project lifecycle from creation to delivery. Keywords: IFC project, schema selection, IFC2X3, IFC4, IFC4X3, units, georeference, coordinate reference system, project template, Bonsai project, CRS, EPSG, WGS84, map coordinates, start new project.
license	MIT
compatibility	Designed for Claude Code. Requires Python 3.x.
metadata	{"author":"OpenAEC-Foundation","version":"1.0"}

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"

Schema	Use Case	IfcProject Required?	Georeferencing
IFC2X3	Legacy, government compliance	YES	ePSet_MapConversion (property set)
IFC4	Buildings (recommended default)	YES	IfcMapConversion + IfcProjectedCRS
IFC4X3	Infrastructure + buildings	YES	IfcMapConversion/IfcMapConversionScaled + IfcProjectedCRS

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

Prefix	Factor	Typical Use
"MILLI"	10⁻³	mm — architecture, structural (most common)
None	1	m — site planning, infrastructure
"CENTI"	10⁻²	cm — rarely used in IFC
"KILO"	10³	km — large-scale infrastructure

Conversion-Based Unit Names

Name	Unit Type	Use
"foot"	LENGTHUNIT	US Imperial length
"inch"	LENGTHUNIT	US Imperial detail
"yard"	LENGTHUNIT	US Imperial site
"square foot"	AREAUNIT	US Imperial area
"cubic foot"	VOLUMEUNIT	US Imperial volume
"degree"	PLANEANGLEUNIT	Angle measurement

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

EPSG Code	Name	Region
EPSG:28992	Amersfoort / RD New	Netherlands
EPSG:32632	WGS 84 / UTM zone 32N	Central Europe
EPSG:32633	WGS 84 / UTM zone 33N	Eastern Europe
EPSG:27700	OSGB 1936 / British National Grid	United Kingdom
EPSG:2154	RGF93 v1 / Lambert-93	France
EPSG:25832	ETRS89 / UTM zone 32N	Germany, Denmark, Austria
EPSG:2056	CH1903+ / LV95	Switzerland
EPSG:3857	WGS 84 / Pseudo-Mercator	Web mapping (NOT for construction)
EPSG:7856	GDA2020 / MGA zone 56	Australia (East)
EPSG:2263	NAD83 / New York Long Island (ftUS)	New York, USA

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

Context Type	Identifier	Target View	Purpose
"Model"	"Body"	"MODEL_VIEW"	Primary 3D geometry (REQUIRED)
"Model"	"Axis"	"GRAPH_VIEW"	Centerline representations
"Model"	"Box"	"MODEL_VIEW"	Bounding box for clash detection
"Model"	"FootPrint"	"MODEL_VIEW"	Floor plan footprint
"Model"	"Clearance"	"MODEL_VIEW"	Clearance volumes
"Plan"	"Annotation"	"PLAN_VIEW"	2D annotations
"Plan"	"Axis"	"PLAN_VIEW"	2D centerlines

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/