Refactor MjcPhysics EqualityJointAPI polynomial coefficients.

The single array attribute `mjc:polycoef` has been replaced by five individual double attributes: `mjc:coef0`, `mjc:coef1`, `mjc:coef2`, `mjc:coef3`, and `mjc:coef4`.

PiperOrigin-RevId: 865947359
Change-Id: If9d14a77b0a06e5dc712eeadd6e9402411570706

include/mujoco/experimental/usd/mjcPhysics/equalityJointAPI.h

@@ -150,35 +150,124 @@ class MjcPhysicsEqualityJointAPI : public UsdAPISchemaBase {
 
  public:
   // --------------------------------------------------------------------- //
-  // POLYCOEF
+  // COEF0
   // --------------------------------------------------------------------- //
-  /// Coefficients a0 through a4 of the quartic polynomial. If the joint values
+  /// Constant coefficient a0 of the quartic polynomial. The constraint is:
-  /// of the constrained joint and reference joint are respectively y and x, and
+  /// y = y0 + a0 + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4.
-  /// their reference positions (corresponding to the joint values in the
-  /// initial model configuration) are y0 and x0, the constraint is: y = y0 + a0
-  /// + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4. Omitting the target
-  /// joint (joint2) is equivalent to setting x = x0, in which case the
-  /// constraint is y = y0 + a0. The default [0, 1, 0, 0, 0] creates a simple
-  /// 1:1 mimic constraint where y tracks x with the same offset from their
-  /// references.
   ///
   /// | ||
   /// | -- | -- |
-  /// | Declaration | `uniform double[] mjc:polycoef = [0, 1, 0, 0, 0]` |
+  /// | Declaration | `uniform double mjc:coef0 = 0` |
-  /// | C++ Type | VtArray<double> |
+  /// | C++ Type | double |
-  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->DoubleArray |
+  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Double |
   /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
   MJCPHYSICS_API
-  UsdAttribute GetPolycoefAttr() const;
+  UsdAttribute GetCoef0Attr() const;
 
-  /// See GetPolycoefAttr(), and also
+  /// See GetCoef0Attr(), and also
   /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
   /// If specified, author \p defaultValue as the attribute's default,
   /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
   /// the default for \p writeSparsely is \c false.
   MJCPHYSICS_API
-  UsdAttribute CreatePolycoefAttr(VtValue const& defaultValue = VtValue(),
+  UsdAttribute CreateCoef0Attr(VtValue const& defaultValue = VtValue(),
-                                  bool writeSparsely = false) const;
+                               bool writeSparsely = false) const;
+
+ public:
+  // --------------------------------------------------------------------- //
+  // COEF1
+  // --------------------------------------------------------------------- //
+  /// Linear coefficient a1 of the quartic polynomial.
+  ///
+  /// | ||
+  /// | -- | -- |
+  /// | Declaration | `uniform double mjc:coef1 = 1` |
+  /// | C++ Type | double |
+  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Double |
+  /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
+  MJCPHYSICS_API
+  UsdAttribute GetCoef1Attr() const;
+
+  /// See GetCoef1Attr(), and also
+  /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
+  /// If specified, author \p defaultValue as the attribute's default,
+  /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
+  /// the default for \p writeSparsely is \c false.
+  MJCPHYSICS_API
+  UsdAttribute CreateCoef1Attr(VtValue const& defaultValue = VtValue(),
+                               bool writeSparsely = false) const;
+
+ public:
+  // --------------------------------------------------------------------- //
+  // COEF2
+  // --------------------------------------------------------------------- //
+  /// Quadratic coefficient a2 of the quartic polynomial.
+  ///
+  /// | ||
+  /// | -- | -- |
+  /// | Declaration | `uniform double mjc:coef2 = 0` |
+  /// | C++ Type | double |
+  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Double |
+  /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
+  MJCPHYSICS_API
+  UsdAttribute GetCoef2Attr() const;
+
+  /// See GetCoef2Attr(), and also
+  /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
+  /// If specified, author \p defaultValue as the attribute's default,
+  /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
+  /// the default for \p writeSparsely is \c false.
+  MJCPHYSICS_API
+  UsdAttribute CreateCoef2Attr(VtValue const& defaultValue = VtValue(),
+                               bool writeSparsely = false) const;
+
+ public:
+  // --------------------------------------------------------------------- //
+  // COEF3
+  // --------------------------------------------------------------------- //
+  /// Cubic coefficient a3 of the quartic polynomial.
+  ///
+  /// | ||
+  /// | -- | -- |
+  /// | Declaration | `uniform double mjc:coef3 = 0` |
+  /// | C++ Type | double |
+  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Double |
+  /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
+  MJCPHYSICS_API
+  UsdAttribute GetCoef3Attr() const;
+
+  /// See GetCoef3Attr(), and also
+  /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
+  /// If specified, author \p defaultValue as the attribute's default,
+  /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
+  /// the default for \p writeSparsely is \c false.
+  MJCPHYSICS_API
+  UsdAttribute CreateCoef3Attr(VtValue const& defaultValue = VtValue(),
+                               bool writeSparsely = false) const;
+
+ public:
+  // --------------------------------------------------------------------- //
+  // COEF4
+  // --------------------------------------------------------------------- //
+  /// Quartic coefficient a4 of the quartic polynomial.
+  ///
+  /// | ||
+  /// | -- | -- |
+  /// | Declaration | `uniform double mjc:coef4 = 0` |
+  /// | C++ Type | double |
+  /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Double |
+  /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
+  MJCPHYSICS_API
+  UsdAttribute GetCoef4Attr() const;
+
+  /// See GetCoef4Attr(), and also
+  /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
+  /// If specified, author \p defaultValue as the attribute's default,
+  /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
+  /// the default for \p writeSparsely is \c false.
+  MJCPHYSICS_API
+  UsdAttribute CreateCoef4Attr(VtValue const& defaultValue = VtValue(),
+                               bool writeSparsely = false) const;
 
  public:
   // ===================================================================== //

include/mujoco/experimental/usd/mjcPhysics/tokens.h

@@ -195,6 +195,26 @@ struct MjcPhysicsTokensType {
   ///
   /// MjcPhysicsActuator
   const TfToken mjcBiasType;
+  /// \brief "mjc:coef0"
+  ///
+  /// MjcPhysicsEqualityJointAPI
+  const TfToken mjcCoef0;
+  /// \brief "mjc:coef1"
+  ///
+  /// MjcPhysicsEqualityJointAPI
+  const TfToken mjcCoef1;
+  /// \brief "mjc:coef2"
+  ///
+  /// MjcPhysicsEqualityJointAPI
+  const TfToken mjcCoef2;
+  /// \brief "mjc:coef3"
+  ///
+  /// MjcPhysicsEqualityJointAPI
+  const TfToken mjcCoef3;
+  /// \brief "mjc:coef4"
+  ///
+  /// MjcPhysicsEqualityJointAPI
+  const TfToken mjcCoef4;
   /// \brief "mjc:compiler:alignFree"
   ///
   /// MjcPhysicsSceneAPI
@@ -580,10 +600,6 @@ struct MjcPhysicsTokensType {
   ///
   /// MjcPhysicsTendon
   const TfToken mjcPathSegments;
-  /// \brief "mjc:polycoef"
-  ///
-  /// MjcPhysicsEqualityJointAPI
-  const TfToken mjcPolycoef;
   /// \brief "mjc:priority"
   ///
   /// MjcPhysicsCollisionAPI

plugin/usd_decoder/usd_decoder.cc

@@ -1854,23 +1854,12 @@ void ParseConstraint(mjSpec* spec, const pxr::UsdPrim& prim, mjsBody* body,
     }
     // If no target, name2 remains empty, meaning joint1 is fixed to a constant.
 
-    // Parse polycoef attribute for the quartic polynomial coefficients.
+    // Parse individual coefficient attributes for the quartic polynomial.
-    auto polycoef_attr = eq_joint_api.GetPolycoefAttr();
+    eq_joint_api.GetCoef0Attr().Get(&eq->data[0]);
-    if (polycoef_attr.HasAuthoredValue()) {
+    eq_joint_api.GetCoef1Attr().Get(&eq->data[1]);
-      pxr::VtDoubleArray polycoef;
+    eq_joint_api.GetCoef2Attr().Get(&eq->data[2]);
-      polycoef_attr.Get(&polycoef);
+    eq_joint_api.GetCoef3Attr().Get(&eq->data[3]);
-      size_t num_coefs = std::min(polycoef.size(), static_cast<size_t>(5));
+    eq_joint_api.GetCoef4Attr().Get(&eq->data[4]);
-      for (size_t i = 0; i < num_coefs; ++i) {
-        eq->data[i] = polycoef[i];
-      }
-    } else {
-      // Default polycoef [0, 1, 0, 0, 0] for 1:1 mimic.
-      eq->data[0] = 0;
-      eq->data[1] = 1;
-      eq->data[2] = 0;
-      eq->data[3] = 0;
-      eq->data[4] = 0;
-    }
 
     // Parse solver parameters from MjcEqualityAPI.
     auto solref_attr = equality_api.GetSolRefAttr();

src/experimental/usd/mjcPhysics/equalityJointAPI.cpp

@@ -77,14 +77,58 @@ const TfType& MjcPhysicsEqualityJointAPI::_GetTfType() const {
   return _GetStaticTfType();
 }
 
-UsdAttribute MjcPhysicsEqualityJointAPI::GetPolycoefAttr() const {
+UsdAttribute MjcPhysicsEqualityJointAPI::GetCoef0Attr() const {
-  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcPolycoef);
+  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcCoef0);
 }
 
-UsdAttribute MjcPhysicsEqualityJointAPI::CreatePolycoefAttr(
+UsdAttribute MjcPhysicsEqualityJointAPI::CreateCoef0Attr(
     VtValue const& defaultValue, bool writeSparsely) const {
   return UsdSchemaBase::_CreateAttr(
-      MjcPhysicsTokens->mjcPolycoef, SdfValueTypeNames->DoubleArray,
+      MjcPhysicsTokens->mjcCoef0, SdfValueTypeNames->Double,
+      /* custom = */ false, SdfVariabilityUniform, defaultValue, writeSparsely);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::GetCoef1Attr() const {
+  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcCoef1);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::CreateCoef1Attr(
+    VtValue const& defaultValue, bool writeSparsely) const {
+  return UsdSchemaBase::_CreateAttr(
+      MjcPhysicsTokens->mjcCoef1, SdfValueTypeNames->Double,
+      /* custom = */ false, SdfVariabilityUniform, defaultValue, writeSparsely);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::GetCoef2Attr() const {
+  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcCoef2);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::CreateCoef2Attr(
+    VtValue const& defaultValue, bool writeSparsely) const {
+  return UsdSchemaBase::_CreateAttr(
+      MjcPhysicsTokens->mjcCoef2, SdfValueTypeNames->Double,
+      /* custom = */ false, SdfVariabilityUniform, defaultValue, writeSparsely);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::GetCoef3Attr() const {
+  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcCoef3);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::CreateCoef3Attr(
+    VtValue const& defaultValue, bool writeSparsely) const {
+  return UsdSchemaBase::_CreateAttr(
+      MjcPhysicsTokens->mjcCoef3, SdfValueTypeNames->Double,
+      /* custom = */ false, SdfVariabilityUniform, defaultValue, writeSparsely);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::GetCoef4Attr() const {
+  return GetPrim().GetAttribute(MjcPhysicsTokens->mjcCoef4);
+}
+
+UsdAttribute MjcPhysicsEqualityJointAPI::CreateCoef4Attr(
+    VtValue const& defaultValue, bool writeSparsely) const {
+  return UsdSchemaBase::_CreateAttr(
+      MjcPhysicsTokens->mjcCoef4, SdfValueTypeNames->Double,
       /* custom = */ false, SdfVariabilityUniform, defaultValue, writeSparsely);
 }
 
@@ -103,7 +147,9 @@ static inline TfTokenVector _ConcatenateAttributeNames(
 const TfTokenVector& MjcPhysicsEqualityJointAPI::GetSchemaAttributeNames(
     bool includeInherited) {
   static TfTokenVector localNames = {
-      MjcPhysicsTokens->mjcPolycoef,
+      MjcPhysicsTokens->mjcCoef0, MjcPhysicsTokens->mjcCoef1,
+      MjcPhysicsTokens->mjcCoef2, MjcPhysicsTokens->mjcCoef3,
+      MjcPhysicsTokens->mjcCoef4,
   };
   static TfTokenVector allNames = _ConcatenateAttributeNames(
       UsdAPISchemaBase::GetSchemaAttributeNames(true), localNames);

src/experimental/usd/mjcPhysics/generatedSchema.usda

@@ -588,16 +588,26 @@ class "MjcEqualityJointAPI" (
     or angle. Only scalar joint types (slide and hinge) can be used."""
 )
 {
-    uniform double[] mjc:polycoef = [0, 1, 0, 0, 0] (
+    uniform double mjc:coef0 = 0 (
-        displayName = "Polynomial Coefficients"
+        displayName = "Coefficient 0"
-        doc = """Coefficients a0 through a4 of the quartic polynomial. If the joint values
+        doc = """Constant coefficient a0 of the quartic polynomial. The constraint is:
-        of the constrained joint and reference joint are respectively y and x, and their
+        y = y0 + a0 + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4."""
-        reference positions (corresponding to the joint values in the initial model
+    )
-        configuration) are y0 and x0, the constraint is:
+    uniform double mjc:coef1 = 1 (
-        y = y0 + a0 + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4.
+        displayName = "Coefficient 1"
-        Omitting the target joint (joint2) is equivalent to setting x = x0, in which case
+        doc = "Linear coefficient a1 of the quartic polynomial."
-        the constraint is y = y0 + a0. The default [0, 1, 0, 0, 0] creates a simple 1:1
+    )
-        mimic constraint where y tracks x with the same offset from their references."""
+    uniform double mjc:coef2 = 0 (
+        displayName = "Coefficient 2"
+        doc = "Quadratic coefficient a2 of the quartic polynomial."
+    )
+    uniform double mjc:coef3 = 0 (
+        displayName = "Coefficient 3"
+        doc = "Cubic coefficient a3 of the quartic polynomial."
+    )
+    uniform double mjc:coef4 = 0 (
+        displayName = "Coefficient 4"
+        doc = "Quartic coefficient a4 of the quartic polynomial."
     )
 }
 

src/experimental/usd/mjcPhysics/schema.usda

@@ -1121,19 +1121,45 @@ class "MjcEqualityJointAPI" (
     inherits = </APISchemaBase>
 )
 {
-    uniform double[] mjc:polycoef = [0, 1, 0, 0, 0] (
+    uniform double mjc:coef0 = 0 (
         customData = {
-            string apiName = "Polycoef"
+            string apiName = "Coef0"
         }
-        displayName = "Polynomial Coefficients"
+        displayName = "Coefficient 0"
-        doc = """Coefficients a0 through a4 of the quartic polynomial. If the joint values
+        doc = """Constant coefficient a0 of the quartic polynomial. The constraint is:
-        of the constrained joint and reference joint are respectively y and x, and their
+        y = y0 + a0 + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4."""
-        reference positions (corresponding to the joint values in the initial model
+    )
-        configuration) are y0 and x0, the constraint is:
+
-        y = y0 + a0 + a1*(x-x0) + a2*(x-x0)^2 + a3*(x-x0)^3 + a4*(x-x0)^4.
+    uniform double mjc:coef1 = 1 (
-        Omitting the target joint (joint2) is equivalent to setting x = x0, in which case
+        customData = {
-        the constraint is y = y0 + a0. The default [0, 1, 0, 0, 0] creates a simple 1:1
+            string apiName = "Coef1"
-        mimic constraint where y tracks x with the same offset from their references."""
+        }
+        displayName = "Coefficient 1"
+        doc = """Linear coefficient a1 of the quartic polynomial."""
+    )
+
+    uniform double mjc:coef2 = 0 (
+        customData = {
+            string apiName = "Coef2"
+        }
+        displayName = "Coefficient 2"
+        doc = """Quadratic coefficient a2 of the quartic polynomial."""
+    )
+
+    uniform double mjc:coef3 = 0 (
+        customData = {
+            string apiName = "Coef3"
+        }
+        displayName = "Coefficient 3"
+        doc = """Cubic coefficient a3 of the quartic polynomial."""
+    )
+
+    uniform double mjc:coef4 = 0 (
+        customData = {
+            string apiName = "Coef4"
+        }
+        displayName = "Coefficient 4"
+        doc = """Quartic coefficient a4 of the quartic polynomial."""
     )
 }
 

src/experimental/usd/mjcPhysics/tokens.cpp

@@ -47,6 +47,11 @@ MjcPhysicsTokensType::MjcPhysicsTokensType()
       mjcArmature("mjc:armature", TfToken::Immortal),
       mjcBiasPrm("mjc:biasPrm", TfToken::Immortal),
       mjcBiasType("mjc:biasType", TfToken::Immortal),
+      mjcCoef0("mjc:coef0", TfToken::Immortal),
+      mjcCoef1("mjc:coef1", TfToken::Immortal),
+      mjcCoef2("mjc:coef2", TfToken::Immortal),
+      mjcCoef3("mjc:coef3", TfToken::Immortal),
+      mjcCoef4("mjc:coef4", TfToken::Immortal),
       mjcCompilerAlignFree("mjc:compiler:alignFree", TfToken::Immortal),
       mjcCompilerAngle("mjc:compiler:angle", TfToken::Immortal),
       mjcCompilerAutoLimits("mjc:compiler:autoLimits", TfToken::Immortal),
@@ -150,7 +155,6 @@ MjcPhysicsTokensType::MjcPhysicsTokensType()
       mjcPathDivisors("mjc:path:divisors", TfToken::Immortal),
       mjcPathIndices("mjc:path:indices", TfToken::Immortal),
       mjcPathSegments("mjc:path:segments", TfToken::Immortal),
-      mjcPolycoef("mjc:polycoef", TfToken::Immortal),
       mjcPriority("mjc:priority", TfToken::Immortal),
       mjcQpos("mjc:qpos", TfToken::Immortal),
       mjcQvel("mjc:qvel", TfToken::Immortal),
@@ -235,6 +239,11 @@ MjcPhysicsTokensType::MjcPhysicsTokensType()
                  mjcArmature,
                  mjcBiasPrm,
                  mjcBiasType,
+                 mjcCoef0,
+                 mjcCoef1,
+                 mjcCoef2,
+                 mjcCoef3,
+                 mjcCoef4,
                  mjcCompilerAlignFree,
                  mjcCompilerAngle,
                  mjcCompilerAutoLimits,
@@ -331,7 +340,6 @@ MjcPhysicsTokensType::MjcPhysicsTokensType()
                  mjcPathDivisors,
                  mjcPathIndices,
                  mjcPathSegments,
-                 mjcPolycoef,
                  mjcPriority,
                  mjcQpos,
                  mjcQvel,