Add Newton physics backend with XPBD solver support #89
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Complete Newton physics backend implementation for the ARK simulator framework. This adds Newton as a fourth backend option alongside PyBullet, MuJoCo, and Genesis. The Newton backend provides GPU-accelerated physics simulation using Newton's XPBD (Extended Position-Based Dynamics) solver with full integration into ARK's existing architecture. Core Framework Changes: - simulator_node.py: Added Newton backend option to backend selection logic. When backend_type: "newton" is specified, the simulator imports and instantiates NewtonBackend. - subscriber.py: Minor enhancement to subscriber handling for improved message processing. Newton Backend Implementation: - newton_backend.py: Main backend class implementing SimulatorBackend ABC. Handles initialization, physics stepping, collision detection, and component lifecycle management. Configurable via YAML with gravity, substeps, solver iterations, and joint control parameters. - newton_builder.py: Wrapper around Newton's ModelBuilder with comprehensive defensive programming. Provides safe URDF loading, joint configuration defaults, and scene metadata tracking. - newton_robot_driver.py: Robot driver implementing RobotDriver interface. Supports TARGET_POSITION, TARGET_VELOCITY, and FORCE joint control modes. Publishes joint_state_t and subscribes to joint_group_command_t for arm/gripper control. - newton_camera_driver.py: Camera sensor driver for RGB and depth capture using Newton's viewer for GPU-accelerated rendering. - newton_lidar_driver.py: LiDAR sensor driver using Newton's ray-casting capabilities with configurable scan parameters. - newton_multibody.py: Rigid body management for non-articulated objects (cubes, spheres, etc.). - newton_viewer.py: Viewer manager supporting GUI mode (OpenGL) and headless mode for render loop and state visualization. - geometry_descriptors.py: Solver-agnostic geometry representation for shape descriptors adaptable to different Newton solvers. Solver Adapters: - scene_adapters/base_adapter.py: Abstract base class defining the adapter interface for solver-specific scene building. - scene_adapters/xpbd_adapter.py: XPBD solver adapter using Newton's native add_ground_plane() and standard contact handling. - scene_adapters/mujoco_adapter.py: MuJoCo solver adapter with workaround for ground plane limitations using box geometry. The Newton backend is 100% Newton-native - it uses only Newton APIs for physics, kinematics, and collision detection.
Refinath
reviewed
Dec 12, 2025
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Contributor
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use 'dict' type instead of Dict
Refinath
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Dec 12, 2025
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| observation_channels: dict[str, type] | None = None, | ||
| action_channels: dict[str, type] | None = None, | ||
| namespace: str = "ark", | ||
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why did you remove this . please keep latest changes
Refinath
reviewed
Dec 12, 2025
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| self.global_config["observation_channels"] = observation_channels | ||
| self.global_config["action_channels"] = action_channels | ||
| self.global_config["namespace"] = namespace | ||
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Please keep the latest changes exists in the main branch [not only these changes]
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Summary
Complete Newton physics backend implementation for the ARK simulator framework. This adds Newton as a fourth backend option alongside PyBullet, MuJoCo, and Genesis.
The Newton backend provides GPU-accelerated physics simulation using Newton's XPBD (Extended Position-Based Dynamics) solver with full integration into ARK's existing architecture.
Files Changed (14 files)
Core Framework Changes (2 files)
ark/system/simulation/simulator_node.pybackend_type: "newton"is specified in config, the simulator now imports and instantiatesNewtonBackend.ark/client/comm_handler/subscriber.pyNewton Backend Implementation (12 files)
ark/system/newton/newton_backend.pySimulatorBackendABC. Handles initialization, physics stepping via XPBD solver, collision detection, and component lifecycle management. Configurable via YAML with gravity, substeps, solver iterations, and joint control parameters.ark/system/newton/newton_builder.pyModelBuilderwith comprehensive defensive programming. Provides safe URDF loading, joint configuration defaults, and scene metadata tracking. Ensures robots are loaded before primitives to preserve body indices.ark/system/newton/newton_robot_driver.pyRobotDriverinterface. Supports TARGET_POSITION, TARGET_VELOCITY, and FORCE joint control modes. Publishesjoint_state_tmessages and subscribes tojoint_group_command_tfor arm/gripper control.ark/system/newton/newton_camera_driver.pyark/system/newton/newton_lidar_driver.pyark/system/newton/newton_multibody.pyark/system/newton/newton_viewer.pyark/system/newton/geometry_descriptors.pySolver Adapters (4 files)
ark/system/newton/scene_adapters/__init__.pyark/system/newton/scene_adapters/base_adapter.pyark/system/newton/scene_adapters/xpbd_adapter.pyadd_ground_plane()and standard contact handling. Default adapter for most use cases.ark/system/newton/scene_adapters/mujoco_adapter.pyArchitecture
The Newton backend follows ARK's existing backend pattern:
SimulatorBackendABC (same interface as PyBullet/MuJoCo backends)NewtonRobotDriverimplementingRobotDriverinterfacebackend_type: "newton"in global config YAMLConfiguration Example
Test Plan
backend_type: "newton"correctly loads NewtonBackendVerification
The Newton backend is 100% Newton-native - it uses only Newton APIs for physics, kinematics, and collision detection. No PyBullet or MuJoCo code is used within the Newton backend implementation.
Future Work (TODO)