Add MuJoCo gravity compensation schema classes

Add MujocoRigidBodyPropertiesCfg with gravity_compensation_scale
(body-level, written to mjc:gravcomp) and MujocoJointDrivePropertiesCfg
with gravity_compensation (joint-level, written to mjc:actuatorgravcomp)
for the Newton/MuJoCo simulation backend.

Both classes use _usd_namespace and _usd_attr_name_map metadata so
the modify functions handle them generically with no backend-specific
branching.

Also extends modify_rigid_body_properties to support _usd_attr_name_map,
matching the joint drive path, for backends with non-camelCase attribute
names.

Author: vidurv-nvidia

source/isaaclab/config/extension.toml

@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "4.6.2"
+version = "4.6.3"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

@@ -1,6 +1,27 @@
 Changelog
 ---------
 
+4.6.3 (2026-04-15)
+~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added :class:`~isaaclab.sim.schemas.MujocoRigidBodyPropertiesCfg` with
+  ``gravity_compensation_scale`` for body-level gravity compensation in the
+  Newton (MuJoCo) backend.
+* Added :class:`~isaaclab.sim.schemas.MujocoJointDrivePropertiesCfg` with
+  ``gravity_compensation`` for joint-level gravity compensation in the
+  Newton (MuJoCo) backend.
+
+Changed
+^^^^^^^
+
+* Extended :meth:`~isaaclab.sim.schemas.modify_rigid_body_properties` to support
+  ``_usd_attr_name_map`` metadata, matching the joint drive path. This enables
+  solver backends with non-camelCase attribute names (e.g. MuJoCo ``mjc:gravcomp``).
+
+
 4.6.2 (2026-04-15)
 ~~~~~~~~~~~~~~~~~~~
 

source/isaaclab/isaaclab/sim/__init__.pyi

@@ -47,6 +47,8 @@ __all__ = [
     "JointDrivePropertiesCfg",
     "MassPropertiesCfg",
     "MeshCollisionPropertiesCfg",
+    "MujocoJointDrivePropertiesCfg",
+    "MujocoRigidBodyPropertiesCfg",
     "PhysxJointDrivePropertiesCfg",
     "PhysxRigidBodyPropertiesCfg",
     "RigidBodyBaseCfg",
@@ -215,6 +217,8 @@ from .schemas import (
     JointDrivePropertiesCfg,
     MassPropertiesCfg,
     MeshCollisionPropertiesCfg,
+    MujocoJointDrivePropertiesCfg,
+    MujocoRigidBodyPropertiesCfg,
     PhysxJointDrivePropertiesCfg,
     PhysxRigidBodyPropertiesCfg,
     RigidBodyBaseCfg,

source/isaaclab/isaaclab/sim/schemas/__init__.pyi

@@ -35,6 +35,8 @@ __all__ = [
     "JointDrivePropertiesCfg",
     "MassPropertiesCfg",
     "MeshCollisionPropertiesCfg",
+    "MujocoJointDrivePropertiesCfg",
+    "MujocoRigidBodyPropertiesCfg",
     "PhysxJointDrivePropertiesCfg",
     "PhysxRigidBodyPropertiesCfg",
     "RigidBodyBaseCfg",
@@ -79,6 +81,8 @@ from .schemas_cfg import (
     JointDrivePropertiesCfg,
     MassPropertiesCfg,
     MeshCollisionPropertiesCfg,
+    MujocoJointDrivePropertiesCfg,
+    MujocoRigidBodyPropertiesCfg,
     PhysxJointDrivePropertiesCfg,
     PhysxRigidBodyPropertiesCfg,
     RigidBodyBaseCfg,

source/isaaclab/isaaclab/sim/schemas/schemas.py

@@ -320,6 +320,7 @@ def modify_rigid_body_properties(
     # read solver-specific metadata from the cfg instance
     namespace = getattr(cfg, "_usd_namespace", None)
     applied_schema = getattr(cfg, "_usd_applied_schema", None)
+    attr_name_map = getattr(cfg, "_usd_attr_name_map", {})
 
     # convert to dict, filtering out class metadata (underscore-prefixed keys)
     cfg_dict = {k: v for k, v in cfg.to_dict().items() if not k.startswith("_")}
@@ -329,7 +330,7 @@ def modify_rigid_body_properties(
         value = cfg_dict.pop(attr_name, None)
         safe_set_attribute_on_usd_schema(usd_rigid_body_api, attr_name, value, camel_case=True)
 
-    # set solver-specific properties using class metadata (namespace + applied schema)
+    # set solver-specific properties using class metadata (namespace + applied schema + attr name map)
     if cfg_dict:
         if namespace is None:
             raise ValueError(
@@ -341,9 +342,8 @@ def modify_rigid_body_properties(
             if applied_schema not in rigid_body_prim.GetAppliedSchemas():
                 rigid_body_prim.AddAppliedSchema(applied_schema)
         for attr_name, value in cfg_dict.items():
-            safe_set_attribute_on_usd_prim(
-                rigid_body_prim, f"{namespace}:{to_camel_case(attr_name, 'cC')}", value, camel_case=False
-            )
+            usd_attr_name = attr_name_map.get(attr_name, to_camel_case(attr_name, "cC"))
+            safe_set_attribute_on_usd_prim(rigid_body_prim, f"{namespace}:{usd_attr_name}", value, camel_case=False)
     # success
     return True
 

source/isaaclab/isaaclab/sim/schemas/schemas_cfg.py

@@ -144,6 +144,34 @@ class PhysxRigidBodyPropertiesCfg(RigidBodyBaseCfg):
     """The mass-normalized kinetic energy threshold below which an actor may participate in stabilization."""
 
 
+@configclass
+class MujocoRigidBodyPropertiesCfg(RigidBodyBaseCfg):
+    """MuJoCo-specific rigid body properties.
+
+    Extends :class:`RigidBodyBaseCfg` with properties that are only supported by the
+    Newton (MuJoCo) simulation backend.
+
+    See :meth:`modify_rigid_body_properties` for more information.
+
+    .. note::
+        If the values are None, they are not modified. This is useful when you want to set only a subset of
+        the properties and leave the rest as-is.
+    """
+
+    # -- Class metadata (not dataclass fields) --
+    # Prim attribute namespace for solver-specific fields.
+    _usd_namespace = "mjc"
+    # Mapping from cfg field names to USD attribute names.
+    _usd_attr_name_map = {"gravity_compensation_scale": "gravcomp"}
+
+    gravity_compensation_scale: float | None = None
+    """Scale factor for gravity compensation for the body [dimensionless]. Defaults to None
+    (attribute not written to USD).
+
+    In MuJoCo, ``0.0`` means no compensation and ``1.0`` means full compensation.
+    """
+
+
 @configclass
 class RigidBodyPropertiesCfg(PhysxRigidBodyPropertiesCfg):
     """Deprecated: use :class:`PhysxRigidBodyPropertiesCfg` or :class:`RigidBodyBaseCfg`.
@@ -321,6 +349,32 @@ class PhysxJointDrivePropertiesCfg(JointDriveBaseCfg):
     """
 
 
+@configclass
+class MujocoJointDrivePropertiesCfg(JointDriveBaseCfg):
+    """MuJoCo-specific joint drive properties.
+
+    Extends :class:`JointDriveBaseCfg` with properties that are only supported by the
+    Newton (MuJoCo) simulation backend.
+
+    See :meth:`modify_joint_drive_properties` for more information.
+
+    .. note::
+        If the values are None, they are not modified. This is useful when you want to set only a subset of
+        the properties and leave the rest as-is.
+    """
+
+    # -- Class metadata (not dataclass fields) --
+    # Prim attribute namespace for solver-specific fields.
+    _usd_namespace = "mjc"
+    # Mapping from cfg field names to USD attribute names.
+    _usd_attr_name_map = {"gravity_compensation": "actuatorgravcomp"}
+
+    gravity_compensation: bool | None = None
+    """Whether to enable gravity compensation on the joint. Defaults to None
+    (attribute not written to USD).
+    """
+
+
 @configclass
 class JointDrivePropertiesCfg(PhysxJointDrivePropertiesCfg):
     """Deprecated: use :class:`PhysxJointDrivePropertiesCfg` or :class:`JointDriveBaseCfg`.