Bonsai: support IfcTrimmedCurve arc segments in profile edit (#6929)

Tabbing into an extrusion to edit its profile crashed on Revit-exported
geometry. `tool.Model.convert_curve_to_mesh` handled IfcPolyline,
IfcCompositeCurve, IfcIndexedPolyCurve and IfcCircle, but not
IfcTrimmedCurve. Revit exports a wall/opening profile as an
IfcCompositeCurve mixing polyline segments with trimmed-circle arc
segments, so the recursion hit an IfcTrimmedCurve, fell through to the
else branch, and raised UnsupportedCurveForConversion, aborting the whole
tab-into-edit.

Add an IfcTrimmedCurve branch that reconstructs a circular arc as a
3-point (start, mid, end) arc into an IFCARCINDEX vertex group, matching
how IfcArcIndex segments already round-trip. Trim parameters are read in
the project plane-angle unit and converted to radians; both
IfcParameterValue and IfcCartesianPoint trims are supported; SenseAgreement
is used to unwrap the end angle so the midpoint lands on the swept arc.
Non-circular basis curves still raise UnsupportedCurveForConversion rather
than emit silently wrong geometry.

Verified live in headless Blender on the issue's file: profile #41622 now
imports (27 verts, 5 arc groups) with no exception, and each reconstructed
arc's endpoints coincide (~1e-6) with the endpoints of the adjacent
polyline segments in the composite curve.

Generated with the assistance of an AI coding tool.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/bonsai/bonsai/tool/model.py

@@ -24,7 +24,7 @@ import collections.abc
 import json
 from collections.abc import Callable, Iterable, Sequence
 from copy import deepcopy
-from math import atan, cos, degrees, pi, radians
+from math import atan, atan2, cos, degrees, pi, radians, sin
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -660,6 +660,50 @@ class Model(bonsai.core.tool.Model):
             )
             cls.circles.append([offset, offset + 1])
             cls.edges.append((offset, offset + 1))
+        elif curve.is_a("IfcTrimmedCurve"):
+            # A trimmed circular arc, e.g. a fillet segment inside an IfcCompositeCurve
+            # exported by Revit. Reconstruct it as a 3-point (start, mid, end) arc so it
+            # round-trips through the IFCARCINDEX vertex group like IfcArcIndex segments do.
+            basis_curve = curve.BasisCurve
+            if not basis_curve.is_a("IfcCircle"):
+                raise cls.UnsupportedCurveForConversion(f"Profile has unsupported curve type: {curve}.")
+            circle_position = Matrix(ifcopenshell.util.placement.get_axis2placement(basis_curve.Position).tolist())
+            circle_position.translation *= cls.unit_scale
+            radius = cls.convert_unit_to_si(basis_curve.Radius)
+            # Trim parameters on a circle are angles expressed in the project plane angle unit.
+            angle_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get(), "PLANEANGLEUNIT")
+
+            def _trim_angle(trim: tuple[ifcopenshell.entity_instance, ...]) -> Union[float, None]:
+                # Prefer a parameter (angle) trim, else derive the angle from a cartesian point.
+                for select in trim:
+                    if select.is_a("IfcParameterValue"):
+                        return float(select.wrappedValue) * angle_scale
+                for select in trim:
+                    if select.is_a("IfcCartesianPoint"):
+                        local = circle_position.inverted() @ Vector(cls.convert_unit_to_si(select.Coordinates)).to_3d()
+                        return atan2(local.y, local.x)
+                return None
+
+            angle_1 = _trim_angle(curve.Trim1)
+            angle_2 = _trim_angle(curve.Trim2)
+            if angle_1 is None or angle_2 is None:
+                raise cls.UnsupportedCurveForConversion(f"Profile has unsupported curve type: {curve}.")
+            # SenseAgreement tells us whether the arc runs with (CCW) or against (CW) the
+            # basis curve direction; unwrap the end angle accordingly so the midpoint lands
+            # on the actual swept arc rather than its complement.
+            if curve.SenseAgreement:
+                while angle_2 < angle_1:
+                    angle_2 += 2 * pi
+            else:
+                while angle_2 > angle_1:
+                    angle_2 -= 2 * pi
+            angle_mid = (angle_1 + angle_2) / 2
+            for angle in (angle_1, angle_mid, angle_2):
+                local_point = Vector((radius * cos(angle), radius * sin(angle), 0.0))
+                cls.vertices.append(position @ circle_position @ local_point)
+            cls.arcs.append([offset, offset + 1, offset + 2])
+            cls.edges.append((offset, offset + 1))
+            cls.edges.append((offset + 1, offset + 2))
         else:
             raise cls.UnsupportedCurveForConversion(f"Profile has unsupported curve type: {curve}.")