Granular export

For discipline-specific exchanges you often need to send only a portion of a model — a single storey, the curtain-wall family, the structural elements — but as a self-contained valid IFC file with the surrounding spatial scaffolding intact.

Using model.extract

from compas_ifc.bim import BuildingInformationModel

model = BuildingInformationModel("data/Duplex_A_20110907.ifc")
storey = next(s for s in model.storeys if s.name == "Level 2")

# Returns a new self-contained BuildingInformationModel
sub = model.extract(storey, path="level_2.ifc")

print(len(list(sub.elements())), "elements in the extract")
print(sub.storeys[0].name)              # "Level 2"
print(sub.project is not None)          # IfcProject scaffolding present

What is preserved

By default, extract carries over:

• the spatial scaffolding required for the file to validate (IfcProject → IfcSite → IfcBuilding → IfcBuildingStorey),

• element geometries, materials, property sets, and visual styles,

• type definitions (IfcRelDefinesByType),

• non-spatial relationships (connections, space boundaries, …) where both endpoints are inside the extracted set.

Each of these is opt-out via boolean flags on extract.

Discipline-only subsets

You can pass any iterable of elements:

walls = model.get_elements_by_type("IfcWallStandardCase")
sub = model.extract(walls, path="walls_only.ifc")

Hosted elements (openings, fillers) attached to the extracted walls are included automatically.

Placement chain rectification

Extracted files inherit the placement-chain rectification performed on import: each element’s IfcLocalPlacement.PlacementRelTo points to its spatial parent and the RelativePlacement holds the local frame, so the file opens cleanly in any IFC viewer without “exploded” geometry.