Expose StepKinematics bindings

ocp.toml

@@ -273,6 +273,7 @@ modules = [
 "StepGeom",
 "StepRepr",
 "StepShape",
+"StepKinematics",
 "RWStepDimTol",
 "RWStepVisual",
 "StepDimTol",

tests/test_kinematics.py

@@ -0,0 +1,72 @@
+"""Exercise STEP kinematics entities through the ordinary STEP exchange API."""
+
+import pytest
+
+from OCP.GeomToStep import GeomToStep_MakeAxis2Placement3d
+from OCP.BRepBuilderAPI import BRepBuilderAPI_MakeVertex
+from OCP.gp import gp_Ax2, gp_Pnt
+from OCP.IFSelect import IFSelect_ReturnStatus
+from OCP.STEPControl import STEPControl_Reader, STEPControl_Writer, STEPControl_AsIs
+from OCP.StepData import StepData_Factors
+from OCP.StepKinematics import (
+    StepKinematics_GearPair,
+    StepKinematics_KinematicJoint,
+    StepKinematics_KinematicLink,
+    StepKinematics_RevolutePair,
+)
+from OCP.TCollection import TCollection_HAsciiString
+
+
+def test_kinematics_entity_round_trip(tmp_path):
+    """Preserve concrete types, link references and pair parameters.
+
+    This tests entity exchange, not a complete geometry-bound mechanism or
+    a kinematic solver.
+    """
+    first = StepKinematics_KinematicLink()
+    first.Init(TCollection_HAsciiString("first link"))
+    second = StepKinematics_KinematicLink()
+    second.Init(TCollection_HAsciiString("second link"))
+    joint = StepKinematics_KinematicJoint()
+    joint.Init(TCollection_HAsciiString("shaft joint"), first, second)
+
+    frame = GeomToStep_MakeAxis2Placement3d(gp_Ax2(), StepData_Factors()).Value()
+    common = (
+        TCollection_HAsciiString("pair"),
+        TCollection_HAsciiString("placement"),
+        False,
+        TCollection_HAsciiString(""),
+        frame,
+        frame,
+        joint,
+    )
+    revolute = StepKinematics_RevolutePair()
+    revolute.Init(*common, False, False, False, False, False, True)
+    gear = StepKinematics_GearPair()
+    gear.Init(*common, 10.0, 20.0, 0.0, 0.0, 2.0)
+
+    writer = STEPControl_Writer()
+    assert writer.Transfer(BRepBuilderAPI_MakeVertex(gp_Pnt()).Vertex(), STEPControl_AsIs) == IFSelect_ReturnStatus.IFSelect_RetDone
+    model = writer.Model()
+    model.AddWithRefs(revolute)
+    model.AddWithRefs(gear)
+    path = str(tmp_path / "kinematics.step")
+    assert writer.Write(path) == IFSelect_ReturnStatus.IFSelect_RetDone
+
+    reader = STEPControl_Reader()
+    assert reader.ReadFile(path) == IFSelect_ReturnStatus.IFSelect_RetDone
+    loaded = reader.StepModel()
+    entities = [loaded.Value(i) for i in range(1, loaded.NbEntities() + 1)]
+    restored_revolute, = [
+        e for e in entities if isinstance(e, StepKinematics_RevolutePair)
+    ]
+    restored_gear, = [
+        e for e in entities if isinstance(e, StepKinematics_GearPair)
+    ]
+    assert restored_revolute.RZ()
+    assert not restored_revolute.TZ()
+    assert restored_gear.GearRatio() == pytest.approx(2.0)
+    assert restored_gear.RadiusFirstLink() == pytest.approx(10.0)
+    assert restored_gear.RadiusSecondLink() == pytest.approx(20.0)
+    assert restored_revolute.Joint().EdgeStart().Name().ToCString() == "first link"
+    assert restored_gear.Joint().EdgeEnd().Name().ToCString() == "second link"