Rod Api and its attachment

newton_usd_schemas/generatedSchema.usda

@@ -866,6 +866,81 @@ class NewtonMaterialAPI "NewtonMaterialAPI" (
     )
 }
 
+class NewtonCurvesDeformableMaterialAPI "NewtonCurvesDeformableMaterialAPI" (
+    apiSchemas = ["PhysicsMaterialAPI"]
+    doc = """Newton extension material parameters for AOUSD curve deformables.
+
+    Apply this API to the same `Material` prim that carries
+    `PhysicsCurvesDeformableMaterialAPI`. The standard AOUSD API owns curve thickness
+    and stretch/shear/bend/twist stiffness; this API only stores Newton-specific
+    controls that are not part of the AOUSD curve material schema.
+
+    Newton's curve-deformable runtime requires Young's modulus `E` and Poisson ratio
+    `nu` to be provided by the AOUSD curve material schema once those attributes are
+    standardized;  `E` governs stretch and bend response, while `E` and `nu` determine 
+    the shear modulus `G = E / (2 * (1 + nu))`, which governs shear and twist response. 
+    Converting these material moduli into discrete stretch/shear/bend/twist stiffness
+    also depends on cross-sectional area, second and polar moments of area, shear correction, 
+    segment rest length, and the solver's rod discretization."""
+)
+{
+    float newton:stretchDamping = -inf (
+        doc = """Newton stretch damping for curve deformables.
+
+        AOUSD curve materials do not define solver damping. If set to -inf, the importer
+        should use its simulator default.
+
+        Range: [0, inf)"""
+        limits = {
+            dictionary soft = {
+                float minimum = 0
+            }
+        }
+    )
+
+    float newton:shearDamping = -inf (
+        doc = """Newton shear damping for curve deformables.
+
+        AOUSD curve materials do not define solver damping. If set to -inf, the importer
+        should use its simulator default.
+
+        Range: [0, inf)"""
+        limits = {
+            dictionary soft = {
+                float minimum = 0
+            }
+        }
+    )
+
+    float newton:bendDamping = -inf (
+        doc = """Newton bend damping for curve deformables.
+
+        AOUSD curve materials do not define solver damping. If set to -inf, the importer
+        should use its simulator default.
+
+        Range: [0, inf)"""
+        limits = {
+            dictionary soft = {
+                float minimum = 0
+            }
+        }
+    )
+
+    float newton:twistDamping = -inf (
+        doc = """Newton twist damping for curve deformables.
+
+        AOUSD curve materials do not define solver damping. If set to -inf, the importer
+        should use its simulator default.
+
+        Range: [0, inf)"""
+        limits = {
+            dictionary soft = {
+                float minimum = 0
+            }
+        }
+    )
+}
+
 class NewtonMimicAPI "NewtonMimicAPI" (
     doc = """`NewtonMimicAPI` applies on top of a `PhysicsJoint`, adding additional constraints to mimic the DOFs of another joint.
 
@@ -945,7 +1020,7 @@ class NewtonActuator "NewtonActuator" (
 
         Currently only the first target is honored, and it must identify either a
         `PhysicsRevoluteJoint` or `PhysicsPrismaticJoint`.
-        
+
         Multi-DOF `PhysicsJoint` prims are not supported, even when locked via `LimitAPI` to a single axis.
         """
     )

newton_usd_schemas/plugInfo.json

@@ -304,6 +304,20 @@
               "apiSchemaCanOnlyApplyTo": [
                 "NewtonActuator"
               ]
+            },
+            "NewtonPhysicsCurvesDeformableMaterialAPI": {
+              "schemaIdentifier": "NewtonCurvesDeformableMaterialAPI",
+              "alias": {
+                "UsdSchemaBase": "NewtonCurvesDeformableMaterialAPI"
+              },
+              "autoGenerated": false,
+              "bases": [
+                "UsdAPISchemaBase"
+              ],
+              "schemaKind": "singleApplyAPI",
+              "apiSchemaCanOnlyApplyTo": [
+                "Material"
+              ]
             }
           }
         },

tests/test_rods.py

@@ -0,0 +1,83 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 The Newton Developers
+# SPDX-License-Identifier: Apache-2.0
+
+import math
+import unittest
+
+from pxr import Plug, Usd, UsdShade
+
+import newton_usd_schemas  # noqa: F401
+
+USD_HAS_LIMITS = Usd.GetVersion() >= (0, 25, 11)
+
+
+class TestNewtonCurvesDeformableMaterialAPI(unittest.TestCase):
+    def setUp(self):
+        self.stage: Usd.Stage = Usd.Stage.CreateInMemory()
+        self.material = UsdShade.Material.Define(self.stage, "/CableMaterial").GetPrim()
+
+    def test_api_registered(self):
+        plug_type = Plug.Registry().FindTypeByName("NewtonPhysicsCurvesDeformableMaterialAPI")
+        self.assertEqual(plug_type.typeName, "NewtonPhysicsCurvesDeformableMaterialAPI")
+        schema_type = Usd.SchemaRegistry().GetSchemaTypeName("NewtonPhysicsCurvesDeformableMaterialAPI")
+        self.assertEqual(schema_type, "NewtonCurvesDeformableMaterialAPI")
+
+    def test_api_application(self):
+        self.assertFalse(self.material.HasAPI("NewtonCurvesDeformableMaterialAPI"))
+        self.material.ApplyAPI("NewtonCurvesDeformableMaterialAPI")
+        self.assertTrue(self.material.HasAPI("PhysicsMaterialAPI"))
+        self.assertTrue(self.material.HasAPI("NewtonCurvesDeformableMaterialAPI"))
+
+        for name in (
+            "newton:stretchDamping",
+            "newton:shearDamping",
+            "newton:bendDamping",
+            "newton:twistDamping",
+        ):
+            self.assertTrue(self.material.HasAttribute(name), name)
+
+    def test_api_limitations(self):
+        prim = self.stage.DefinePrim("/NotMaterial", "Xform")
+        self.assertFalse(prim.CanApplyAPI("NewtonCurvesDeformableMaterialAPI"))
+        self.assertTrue(self.material.CanApplyAPI("NewtonCurvesDeformableMaterialAPI"))
+
+    def test_material_parameter_defaults(self):
+        self.material.ApplyAPI("NewtonCurvesDeformableMaterialAPI")
+        self.assertEqual(self.material.GetAttribute("newton:stretchDamping").Get(), -math.inf)
+        self.assertEqual(self.material.GetAttribute("newton:shearDamping").Get(), -math.inf)
+        self.assertEqual(self.material.GetAttribute("newton:bendDamping").Get(), -math.inf)
+        self.assertEqual(self.material.GetAttribute("newton:twistDamping").Get(), -math.inf)
+
+    def test_material_parameter_roundtrip(self):
+        self.material.ApplyAPI("NewtonCurvesDeformableMaterialAPI")
+
+        values = {
+            "newton:stretchDamping": 0.01,
+            "newton:shearDamping": 0.02,
+            "newton:bendDamping": 0.03,
+            "newton:twistDamping": 0.04,
+        }
+        for name, value in values.items():
+            attr = self.material.GetAttribute(name)
+            self.assertTrue(attr.Set(value), name)
+            self.assertAlmostEqual(attr.Get(), value)
+
+    def test_limits(self):
+        if not USD_HAS_LIMITS:
+            self.skipTest("USD build does not expose schema limits")
+
+        self.material.ApplyAPI("NewtonCurvesDeformableMaterialAPI")
+        for name in (
+            "newton:stretchDamping",
+            "newton:shearDamping",
+            "newton:bendDamping",
+            "newton:twistDamping",
+        ):
+            limits = self.material.GetAttribute(name).GetSoftLimits()
+            self.assertTrue(limits.IsValid(), name)
+            self.assertEqual(limits.GetMinimum(), 0.0)
+            self.assertIsNone(limits.GetMaximum())
+
+
+if __name__ == "__main__":
+    unittest.main()