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Extract space generation algorithms to ifcopenshell.util
Move Blender-independent space generation algorithms from Bonsai (GPL) to ifcopenshell.util (LGPL): - ifcopenshell.util.shape.bisect_mesh_plane_vf: vectorized numpy triangle/plane intersection for mesh bisection - ifcopenshell.util.element.iter_top_connections: walker for IfcRelConnectsElements(TOP) relationships - ifcopenshell.util.space: new module with get_boundary_lines, get_space_polygon, get_auto_space_height and height detection helpers — all operating on IFC geometry without Blender Bonsai's tool/spatial.py now delegates to these utilities via thin wrappers, keeping only Blender-specific concerns (cache management with depsgraph invalidation, UI property reads). tool/wall.py iter_wall_slab_connections delegates to ifcopenshell.util.element.iter_top_connections. Added 22 tests: 6 for bisect_mesh_plane_vf, 10 for space generation algorithms, 4 for iter_top_connections, 2 Bonsai integration tests for cache behavior. Generated with the assistance of an AI coding tool.
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CyrilWaechter
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# IfcOpenShell - IFC toolkit and geometry engine
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# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
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#
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# This file is part of IfcOpenShell.
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#
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# IfcOpenShell is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# IfcOpenShell is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with IfcOpenShell. If not, see <http://www.gnu.org/licenses/>.
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"""Blender-independent utilities for space geometry generation.
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These functions operate on IFC geometry data (vertices, faces, element
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relationships) without requiring any Blender objects to be loaded. They are
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used by Bonsai's space generation pipeline but can also be used standalone
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for IFC analysis.
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"""
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from __future__ import annotations
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from typing import Optional, Union
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import ifcopenshell
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import ifcopenshell.util.element
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import ifcopenshell.util.shape
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import shapely
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BOUNDING_CLASSES = ("IfcWall", "IfcColumn", "IfcMember", "IfcVirtualElement", "IfcPlate")
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HEIGHT_DETECTION_CLASSES = ("IfcSlab", "IfcRoof")
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def get_boundary_lines(
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ifc_file: ifcopenshell.file,
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shapes: dict,
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cut_z: float,
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bounding_classes: tuple = BOUNDING_CLASSES,
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) -> tuple[list[shapely.LineString], list[ifcopenshell.entity_instance]]:
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"""Generate boundary lines by bisecting IFC element geometry with a horizontal plane.
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:param ifc_file: The IFC file.
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:param shapes: Dict of element shapes keyed by element id, as produced by
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a geometry cache. Each entry must have ``verts`` (n,3 ndarray),
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``faces`` (m,3 ndarray), ``bottom_z`` (float), ``top_z`` (float).
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:param cut_z: Z elevation of the cutting plane in world coordinates.
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:param bounding_classes: IFC classes to treat as space-bounding elements.
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:return: ``(boundary_lines, bounding_elements)`` where boundary_lines is a
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list of shapely LineString segments and bounding_elements is a list of
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IFC entity instances that intersect the cutting plane.
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"""
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boundary_lines: list[shapely.LineString] = []
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bounding_elements: list[ifcopenshell.entity_instance] = []
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for element_id, shape_data in shapes.items():
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element = ifc_file.by_id(element_id)
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if not any(element.is_a(cls) for cls in bounding_classes):
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continue
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if cut_z <= shape_data["bottom_z"] or cut_z >= shape_data["top_z"]:
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continue
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bounding_elements.append(element)
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segments = ifcopenshell.util.shape.bisect_mesh_plane_vf(
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shape_data["verts"], shape_data["faces"], cut_z, precision=3, extend=0.05
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)
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for start, end in segments:
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boundary_lines.append(shapely.LineString([start, end]))
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return boundary_lines, bounding_elements
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def get_space_polygon(
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boundary_lines: list[shapely.LineString],
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x: float,
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y: float,
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) -> tuple[Union[shapely.Polygon, str], list]:
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"""Assemble boundary lines into closed polygons and find the one containing (x, y).
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:param boundary_lines: List of shapely LineString segments forming a planar graph.
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:param x: X coordinate of the point to test.
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:param y: Y coordinate of the point to test.
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:return: ``(polygon, [])`` on success, or ``("NO POLYGONS FOUND", [])`` /
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``("NO POLYGON FOR POINT", [])`` on failure. The second element is
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reserved for bounding elements (returned by the caller from
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:func:`get_boundary_lines`).
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"""
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unioned = shapely.union_all(shapely.GeometryCollection(boundary_lines))
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closed_polygons = shapely.polygonize(unioned.geoms)
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if not closed_polygons:
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return "NO POLYGONS FOUND", []
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for polygon in closed_polygons.geoms:
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if shapely.contains_xy(polygon, x, y):
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return shapely.force_3d(polygon), []
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return "NO POLYGON FOR POINT", []
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def get_auto_space_height(
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ifc_file: ifcopenshell.file,
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shapes: dict,
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space_polygon: shapely.Polygon,
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base_z: float,
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bounding_walls: list[ifcopenshell.entity_instance],
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) -> Optional[float]:
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"""Auto-detect space height from elements above using IFC geometry.
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Detection priority:
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1. ``IfcRelConnectsElements`` (TOP) connections on bounding walls
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2. ``IfcSlab`` / ``IfcRoof`` elements above with XY overlap to the space polygon
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3. Minimum wall top Z of bounding walls
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:param ifc_file: The IFC file.
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:param shapes: Dict of element shapes keyed by element id (see :func:`get_boundary_lines`).
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:param space_polygon: The space footprint polygon in world XY.
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:param base_z: The space's base Z in world coordinates.
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:param bounding_walls: List of IFC wall elements bounding the space.
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:return: Detected height in meters, or ``None`` if nothing found.
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"""
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height = get_height_from_top_connections(ifc_file, shapes, bounding_walls, base_z, space_polygon)
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if height is not None and height > 0:
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return height
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height = get_height_from_elements_above(ifc_file, shapes, space_polygon, base_z)
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if height is not None and height > 0:
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return height
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height = get_height_from_wall_tops(shapes, bounding_walls, base_z)
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if height is not None and height > 0:
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return height
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return None
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def get_height_from_top_connections(
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ifc_file: ifcopenshell.file,
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shapes: dict,
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bounding_walls: list[ifcopenshell.entity_instance],
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base_z: float,
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space_polygon: shapely.Polygon,
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) -> Optional[float]:
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"""Find the lowest bottom face of elements connected to bounding walls via IfcRelConnectsElements(TOP).
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:param ifc_file: The IFC file.
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:param shapes: Dict of element shapes keyed by element id.
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:param bounding_walls: List of IFC wall elements.
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:param base_z: The space's base Z in world coordinates.
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:param space_polygon: The space footprint polygon in world XY.
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:return: Height in meters, or ``None``.
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"""
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lowest_min_z: Optional[float] = None
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for wall_element in bounding_walls:
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for connected_element, _rel in ifcopenshell.util.element.iter_top_connections(wall_element):
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if not (connected_element.is_a("IfcSlab") or connected_element.is_a("IfcRoof")):
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continue
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shape_data = shapes.get(connected_element.id())
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if not shape_data:
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continue
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min_z = shape_data["bottom_z"]
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if min_z <= base_z:
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continue
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verts = shape_data["verts"]
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element_box = shapely.box(
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float(verts[:, 0].min()),
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float(verts[:, 1].min()),
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float(verts[:, 0].max()),
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float(verts[:, 1].max()),
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)
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if not element_box.intersects(space_polygon):
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continue
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if lowest_min_z is None or min_z < lowest_min_z:
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lowest_min_z = min_z
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if lowest_min_z is not None:
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return lowest_min_z - base_z
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return None
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def get_height_from_elements_above(
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ifc_file: ifcopenshell.file,
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shapes: dict,
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space_polygon: shapely.Polygon,
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base_z: float,
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height_classes: tuple = HEIGHT_DETECTION_CLASSES,
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) -> Optional[float]:
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"""Find the lowest IfcSlab / IfcRoof above whose XY bbox overlaps the space polygon.
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:param ifc_file: The IFC file.
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:param shapes: Dict of element shapes keyed by element id.
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:param space_polygon: The space footprint polygon in world XY.
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:param base_z: The space's base Z in world coordinates.
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:param height_classes: IFC classes to consider as ceiling elements.
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:return: Height in meters, or ``None``.
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"""
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lowest_min_z: Optional[float] = None
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for ifc_class in height_classes:
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for element in ifc_file.by_type(ifc_class):
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shape_data = shapes.get(element.id())
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if not shape_data:
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continue
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min_z = shape_data["bottom_z"]
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if min_z <= base_z:
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continue
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verts = shape_data["verts"]
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element_box = shapely.box(
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float(verts[:, 0].min()),
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float(verts[:, 1].min()),
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float(verts[:, 0].max()),
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float(verts[:, 1].max()),
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)
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if not element_box.intersects(space_polygon):
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continue
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if lowest_min_z is None or min_z < lowest_min_z:
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lowest_min_z = min_z
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if lowest_min_z is not None:
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return lowest_min_z - base_z
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return None
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def get_height_from_wall_tops(
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shapes: dict,
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bounding_walls: list[ifcopenshell.entity_instance],
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base_z: float,
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) -> Optional[float]:
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"""Find the minimum wall top Z among bounding walls.
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:param shapes: Dict of element shapes keyed by element id.
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:param bounding_walls: List of IFC wall elements.
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:param base_z: The space's base Z in world coordinates.
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:return: Height in meters, or ``None``.
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"""
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lowest_top_z: Optional[float] = None
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for wall_element in bounding_walls:
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shape_data = shapes.get(wall_element.id())
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if not shape_data:
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continue
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max_z = shape_data["top_z"]
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if max_z <= base_z:
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continue
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if lowest_top_z is None or max_z < lowest_top_z:
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lowest_top_z = max_z
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if lowest_top_z is not None:
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return lowest_top_z - base_z
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return None
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