[OVPHYSX] Articulation rewrite (data class + asset class + kernels)

Add Articulation and ArticulationData for the OVPhysX backend, mirroring
the PhysX/Newton public API. Resolves PR #5459.

Articulation
^^^^^^^^^^^^

* index/mask split for every state writer, simulation-parameter writer,
  setter, and tendon setter; OVPhysX exposes both _index and _mask as
  first-class paths and intentionally drops the PhysX-specific
  ``full_data`` kwarg.
* Dedicated dynamic + viscous friction setters
  (write_joint_{dynamic,viscous}_friction_coefficient_to_sim_{index,mask})
  that touch only their slot of the combined (N, J, 3)
  DOF_FRICTION_PROPERTIES buffer.  The combined
  write_joint_friction_coefficient_to_sim_index/_mask still accepts all
  three components as kwargs (Coulomb static + dynamic + optional
  viscous) for source-compatible PhysX call sites.
* Deprecated non-indexed shorthand shims for friction (x3) and root /
  joint state (x4), forwarding to the index variants with a
  DeprecationWarning, matching PhysX's deprecated section.
* Wrench-composer return types tightened to non-None
  (instantaneous_wrench_composer / permanent_wrench_composer);
  composers are always set in _create_buffers, mirroring PhysX/Newton.
* Section organisation matches PhysX exactly: Properties -> Operations
  -> Operations - Finders -> Operations - State Writers -> Operations
  - Simulation Parameters Writers -> Operations - Setters -> Operations
  - Tendons -> Internal helper -> Internal simulation callbacks ->
  Internal helpers -- Actuators -> Internal helpers -- Debugging ->
  Deprecated methods.  Section delimiters use bare """Section."""
  docstring blocks (Newton/PhysX convention).

ArticulationData
^^^^^^^^^^^^^^^^

* Pull-on-demand timestamped buffers; CPU-only bindings route through
  pinned-host staging (PR #5329 pattern).
* Property names match PhysX exactly: joint_friction_coeff,
  joint_dynamic_friction_coeff, joint_viscous_friction_coeff (no
  *_static / *_dynamic / *_viscous renames).
* SI units annotated on every public property docstring
  ([m or rad, depending on joint type], [m/s or rad/s, ...], [N*m],
  [kg], etc.) per AGENTS.md.
* binding_getter parameter on __init__ typed as
  Callable[[int], Any] | None.
* Section organisation matches PhysX (Defaults -> Joint commands ->
  Joint properties -> Fixed tendon -> Spatial tendon -> Root state ->
  Body state -> Joint state -> Derived -> Sliced -> Internal helpers ->
  Deprecated properties).

Kernels
^^^^^^^

* Articulation-specific kernels in
  isaaclab_ovphysx/assets/articulation/kernels.py (soft-limit clamp,
  friction-data writer, finite-difference joint-acc helper, body-CoM
  pose composer); shared kernels promoted to
  isaaclab_ovphysx/assets/kernels.py.
* Per-kernel docstrings document purpose, shape/dtype/SI units, and
  divergence notes where the OVPhysX implementation differs (e.g.
  _fd_joint_acc takes inv_dt rather than dt to avoid per-element
  division).

Tests
^^^^^

* Real-backend test_articulation.py mirrors isaaclab_physx 1-to-1
  under run_ovphysx.sh; 99 tests pass on each of CPU + CUDA.
* test_articulation_helpers.py covers the kitless-only helpers
  (tendon scoping, mock binding shapes).
* Cross-backend test_articulation_iface.py runs the OVPhysX path:
  544 tests pass, 16 skipped, 0 failed on each of CPU + CUDA.  Brings
  the iface helper up to the actual ArticulationData constructor
  signature and broadcasts scalar inputs across joint / fixed-tendon
  / spatial-tendon mask setters that previously rejected them.

OVPhysX-only surface dropped
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* Articulation: set_external_force_and_torque_{index,mask} (use
  instantaneous_wrench_composer.add_forces_and_torques_*),
  set_spatial_tendon_limit_{index,mask}, and
  set_spatial_tendon_rest_length_{index,mask} (NotImplementedError
  stubs PhysX never had).
* ArticulationData: body_pose_w / body_lin_vel_w / body_ang_vel_w /
  body_acc_w / body_link_acc_w (base class provides matching
  defaults), body_inv_mass / body_inv_inertia, fixed_tendon_limit
  (PhysX exposes only fixed_tendon_pos_limits), spatial_tendon_limit /
  spatial_tendon_rest_length (no PhysX equivalent).

Author: AntoineRichard

source/isaaclab/test/assets/test_articulation_iface.py

@@ -256,20 +256,27 @@ def create_ovphysx_articulation(
     object.__setattr__(articulation, "_num_spatial_tendons", num_spatial_tendons)
 
     # Create ArticulationData
-    data = OvPhysxArticulationData(mock_bindings.bindings, device)
-    data._num_instances = num_instances
-    data._num_joints = num_joints
-    data._num_bodies = num_bodies
-    data._num_fixed_tendons = num_fixed_tendons
-    data._num_spatial_tendons = num_spatial_tendons
+    data = OvPhysxArticulationData(
+        mock_bindings.bindings,
+        device,
+        num_instances=num_instances,
+        num_bodies=num_bodies,
+        num_joints=num_joints,
+        num_fixed_tendons=num_fixed_tendons,
+        num_spatial_tendons=num_spatial_tendons,
+        body_names=body_names,
+        joint_names=joint_names,
+        fixed_tendon_names=fixed_tendon_names,
+        spatial_tendon_names=spatial_tendon_names,
+    )
     data._is_fixed_base = False
-    data.body_names = body_names
-    data.joint_names = joint_names
-    data.fixed_tendon_names = fixed_tendon_names
-    data.spatial_tendon_names = spatial_tendon_names
-    data._create_buffers()
     object.__setattr__(articulation, "_data", data)
 
+    # Allocate the articulation-side index/mask caches and wrench buffer that
+    # _initialize_impl would normally populate.  Wrench composers created here
+    # are immediately overwritten by the mocks below.
+    articulation._create_buffers()
+
     # Wrench composers
     mock_inst_wrench = MockWrenchComposer(articulation)
     mock_perm_wrench = MockWrenchComposer(articulation)

source/isaaclab_ovphysx/config/extension.toml

@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.2.17"
+version = "0.2.18"
 
 # Description
 title = "OvPhysX simulation interfaces for IsaacLab core package"

source/isaaclab_ovphysx/docs/CHANGELOG.rst

@@ -1,6 +1,79 @@
 Changelog
 ---------
 
+0.2.18 (2026-05-05)
+~~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added :class:`~isaaclab_ovphysx.assets.Articulation` and
+  :class:`~isaaclab_ovphysx.assets.ArticulationData` mirroring the PhysX/Newton
+  articulation API: index/mask split for every state writer, simulation-parameter
+  writer, setter, and tendon setter; pull-on-demand timestamped buffers; first-class
+  CPU-only binding routing through pinned-host staging.
+* Added dedicated :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_dynamic_friction_coefficient_to_sim_index`,
+  :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_dynamic_friction_coefficient_to_sim_mask`,
+  :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_viscous_friction_coefficient_to_sim_index`,
+  and :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_viscous_friction_coefficient_to_sim_mask`
+  to mirror PhysX's per-component friction surface; each touches only its slot in the
+  combined ``(N, J, 3)`` ``DOF_FRICTION_PROPERTIES`` buffer.
+* Added deprecated non-indexed shorthand shims
+  :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_friction_coefficient_to_sim`,
+  :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_dynamic_friction_coefficient_to_sim`,
+  and :meth:`~isaaclab_ovphysx.assets.Articulation.write_joint_viscous_friction_coefficient_to_sim`
+  for migration parity with PhysX.
+
+Changed
+^^^^^^^
+
+* Reorganized :class:`~isaaclab_ovphysx.assets.Articulation` and
+  :class:`~isaaclab_ovphysx.assets.ArticulationData` to mirror PhysX's section
+  layout exactly: bare ``"""Section."""`` docstring blocks (replacing
+  ``# --- Section ---`` comment banners), with internal helpers and deprecated
+  surface placed at the bottom of each class.
+* Renamed the three friction-coefficient properties on
+  :class:`~isaaclab_ovphysx.assets.ArticulationData` to match PhysX:
+  ``joint_friction_static`` → :attr:`~isaaclab_ovphysx.assets.ArticulationData.joint_friction_coeff`,
+  ``joint_friction_dynamic`` → :attr:`~isaaclab_ovphysx.assets.ArticulationData.joint_dynamic_friction_coeff`,
+  ``joint_friction_viscous`` → :attr:`~isaaclab_ovphysx.assets.ArticulationData.joint_viscous_friction_coeff`.
+* Tightened :attr:`~isaaclab_ovphysx.assets.Articulation.instantaneous_wrench_composer`
+  and :attr:`~isaaclab_ovphysx.assets.Articulation.permanent_wrench_composer`
+  return types from ``WrenchComposer | None`` to ``WrenchComposer``,
+  matching PhysX/Newton.
+* Type-annotated ``binding_getter`` on
+  :meth:`~isaaclab_ovphysx.assets.ArticulationData.__init__` as
+  ``Callable[[int], Any] | None``.
+* Expanded docstrings on the OVPhysX articulation Warp kernels
+  (:func:`~isaaclab_ovphysx.assets.articulation.kernels.compute_soft_joint_pos_limits_func`,
+  :func:`~isaaclab_ovphysx.assets.articulation.kernels.update_soft_joint_pos_limits`,
+  :func:`~isaaclab_ovphysx.assets.articulation.kernels._fd_joint_acc`) to match
+  PhysX's documentation depth (purpose, ``Args:`` table with shape/dtype/SI units,
+  divergence notes where the OVPhysX implementation differs).
+
+Removed
+^^^^^^^
+
+* Removed OVPhysX-only :meth:`~isaaclab_ovphysx.assets.Articulation.set_external_force_and_torque_index`
+  and :meth:`~isaaclab_ovphysx.assets.Articulation.set_external_force_and_torque_mask`.
+  Use :attr:`~isaaclab_ovphysx.assets.Articulation.instantaneous_wrench_composer` /
+  :attr:`~isaaclab_ovphysx.assets.Articulation.permanent_wrench_composer` and call
+  ``add_forces_and_torques_index`` / ``add_forces_and_torques_mask`` on the composer
+  directly, matching PhysX/Newton.
+* Removed the OVPhysX-only ``set_spatial_tendon_limit_{index,mask}`` and
+  ``set_spatial_tendon_rest_length_{index,mask}`` ``NotImplementedError`` stubs;
+  the equivalents are not exposed by PhysX.
+* Removed redundant or behavior-divergent overrides of base-class shorthand
+  properties on :class:`~isaaclab_ovphysx.assets.ArticulationData`:
+  ``body_pose_w``, ``body_lin_vel_w``, ``body_ang_vel_w``, ``body_acc_w``,
+  ``body_link_acc_w``.  The defaults from
+  :class:`~isaaclab.assets.BaseArticulationData` apply and match PhysX.
+* Removed forward-compat ``body_inv_mass``, ``body_inv_inertia``,
+  ``fixed_tendon_limit``, ``spatial_tendon_limit``, and
+  ``spatial_tendon_rest_length`` properties on
+  :class:`~isaaclab_ovphysx.assets.ArticulationData` along with their backing
+  buffers; these had no PhysX equivalent.
+
 0.2.17 (2026-05-05)
 ~~~~~~~~~~~~~~~~~~~~