IfcOpenShell/src/ifcopenshell-python/ifcopenshell/api/alignment/_create_geometric_representation.py

# IfcOpenShell - IFC toolkit and geometry engine
# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
#
# This file is part of IfcOpenShell.
#
# IfcOpenShell is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# IfcOpenShell is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.


import ifcopenshell
import ifcopenshell.api.alignment
import ifcopenshell.api.geometry
from ifcopenshell import entity_instance


def _create_geometric_representation(file: ifcopenshell.file, alignment: entity_instance) -> None:
    """
    Create geometric representation for the alignment and its nested layouts.

    There are 5 different cases (the IfcCurve created is indicated):

    1) Horizontal only -> IfcCompositeCurve
    2) Horizontal + Vertical -> IfcCompositeCurve and IfcGradientCurve
    3) Horizontal + Vertical + Cant -> IfcCompositeCurve and IfcSegmentedReferentCurve
    4) Vertical only (this occurs when horizontal is reused from a parent alignment) -> IfcGradientCurve
    5) Vertical + Cant (this occurs when horizontal is reused from a parent alignment) -> IfcSegmentedReferenceCurve

    This method creates the geometric representation entity and assigns it to the alignment, but does not populate the geometry of the representation.

    :param alignment: The alignment for which the representation is being created
    :return: None
    """

    expected_type = "IfcAlignment"
    if not alignment.is_a(expected_type):
        raise TypeError(f"Expected {expected_type} but got {alignment.is_a()}")

    axis_geom_subcontext = ifcopenshell.api.alignment.get_axis_subcontext(file)

    layouts = ifcopenshell.api.alignment.get_alignment_layouts(alignment)
    children = ifcopenshell.api.alignment.get_child_alignments(alignment)

    if len(layouts) == 1 and len(children) == 0:
        assert layouts[0].is_a("IfcAlignmentHorizontal")
        # Horizontal only - IFC CT 4.1.7.1.1.1
        composite_curve = file.createIfcCompositeCurve(Segments=[], SelfIntersect=False)
        representation = file.createIfcShapeRepresentation(
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="Axis",
            RepresentationType="Curve2D",
            Items=(composite_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)
    elif len(layouts) == 2 and len(children) == 0:
        # Horizontal and Vertical - IFC CT 4.1.7.1.1.1
        assert layouts[0].is_a("IfcAlignmentHorizontal")
        assert layouts[1].is_a("IfcAlignmentVertical")
        composite_curve = file.createIfcCompositeCurve(Segments=[], SelfIntersect=False)
        representation = file.createIfcShapeRepresentation(
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="FootPrint",
            RepresentationType="Curve2D",
            Items=(composite_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)

        gradient_curve = file.createIfcGradientCurve(Segments=[], BaseCurve=composite_curve, SelfIntersect=False)
        representation = file.createIfcShapeRepresentation(
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="Axis",
            RepresentationType="Curve3D",
            Items=(gradient_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)
    elif len(layouts) == 3 and len(children) == 0:
        # Horizontal, Vertical, and Cant - IFC CT 4.1.7.1.1.3
        assert layouts[0].is_a("IfcAlignmentHorizontal")
        assert layouts[1].is_a("IfcAlignmentVertical")
        assert layouts[2].is_a("IfcAlignmentCant")
        composite_curve = file.createIfcCompositeCurve(Segments=[], SelfIntersect=False)
        representation = file.createIfcShapeRepresentation(
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="FootPrint",
            RepresentationType="Curve2D",
            Items=(composite_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)

        gradient_curve = file.createIfcGradientCurve(Segments=[], BaseCurve=composite_curve, SelfIntersect=False)
        segmented_reference_curve = file.createIfcSegmentedReferenceCurve(
            Segments=[], BaseCurve=gradient_curve, SelfIntersect=False
        )
        representation = file.create_entity(
            type="IfcShapeRepresentation",
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="Axis",
            RepresentationType="Curve3D",
            Items=(segmented_reference_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)
    else:
        # Reusing Horizontal - CT 4.1.4.4.1.2
        # Create a representation on the parent alignment
        composite_curve = file.createIfcCompositeCurve(Segments=[], SelfIntersect=False)
        representation = file.createIfcShapeRepresentation(
            ContextOfItems=axis_geom_subcontext,
            RepresentationIdentifier="FootPrint",
            RepresentationType="Curve2D",
            Items=(composite_curve,),
        )
        ifcopenshell.api.geometry.assign_representation(file, alignment, representation)

    for child_alignment in children:
        child_alignment.ObjectPlacement = alignment.ObjectPlacement
        child_layouts = ifcopenshell.api.alignment.get_alignment_layouts(child_alignment)
        if len(child_layouts) == 1:
            assert child_layouts[0].is_a("IfcAlignmentVertical")
            base_curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
            gradient_curve = file.createIfcGradientCurve(Segments=[], BaseCurve=base_curve, SelfIntersect=False)
            representation = file.createIfcShapeRepresentation(
                ContextOfItems=axis_geom_subcontext,
                RepresentationIdentifier="Axis",
                RepresentationType="Curve3D",
                Items=(gradient_curve,),
            )
            ifcopenshell.api.geometry.assign_representation(file, child_alignment, representation)
        elif len(child_layouts) == 2:
            assert child_layouts[0].is_a("IfcAlignmentVertical")
            assert child_layouts[1].is_a("IfcAlignmentCant")
            base_curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
            gradient_curve = file.createIfcGradientCurve(Segments=[], BaseCurve=base_curve, SelfIntersect=False)
            segmented_reference_curve = file.createIfcSegmentedReferenceCurve(
                Segments=[], BaseCurve=gradient_curve, SelfIntersect=False
            )
            representation = file.creatIfcShapeRepresentation(
                ContextOfItems=axis_geom_subcontext,
                RepresentationIdentifier="Axis",
                RepresentationType="Curve3D",
                Items=(segmented_reference_curve,),
            )
            ifcopenshell.api.geometry.assign_representation(file, child_alignment, representation)
        else:
            assert False  # should never get here - can't have more than one vertical and cant in a child alignment