Python API#

The following table summarizes the available classes and functions.

`acquire_physics_interface`	Get the Newton physics interface.
`acquire_stage`	Get the Newton simulation stage.
`configure_newton`	Set the Newton runtime configuration.
`get_newton_config`	Return the live Newton configuration.
`get_active_physics_engine`	Get the name of the currently active physics engine.
`get_available_physics_engines`	Get list of all available physics engines.

Configuration Classes#

`NewtonConfig`	Configuration for Newton physics simulation in Isaac Sim.
`NewtonSolverOutputConfig`	Optional outputs computed by the Newton solver during simulation steps.
`CollisionConfig`	Configuration for the Newton collision pipeline.
`HydroelasticConfig`	Runtime configuration for hydroelastic contact.
`XPBDSolverConfig`	Configuration for XPBD (Extended Position-Based Dynamics) solver.
`MuJoCoSolverConfig`	Configuration for MuJoCo Warp solver-related parameters.

Tensor Interface#

The Newton tensor backend is provided by the separate isaacsim.physics.newton.tensors extension. Its generated Python API lists the simulation and view interfaces available when the extension is loaded.

Functions#

acquire_physics_interface() → NewtonPhysicsInterface | None#

Get the Newton physics interface.

Returns:: The physics interface for controlling simulation, or None if not initialized.

acquire_stage() → NewtonStage | None#

Get the Newton simulation stage.

Function name has a typo (“acuire”) but is kept for backward compatibility.

Returns:: The simulation stage object, or None if not initialized.

configure_newton( cfg: NewtonConfig, ) → None#

Set the Newton runtime configuration.

Applied on the next play or re-initialization. Call before play from a standalone script or extension.

Parameters:: cfg – Newton simulation configuration.

get_newton_config() → NewtonConfig | None#

Return the live Newton configuration.

Returns:: The current or pending configuration, or None if Newton has not been configured.

get_active_physics_engine() → str#

Get the name of the currently active physics engine.

Returns:: Name of the active engine (“newton”, “physx”, etc.) or “Unknown” if none active.

get_available_physics_engines( verbose: bool = False, ) → list[tuple[str, bool]]#

Get list of all available physics engines.

Parameters:: verbose – If True, print available engines to console.
Returns:: List of tuples (engine_name, is_active) for all registered engines.

Configuration Classes#

class NewtonConfig( num_substeps: int = 1, debug_mode: bool = False, use_cuda_graph: bool = True, time_step_app: bool = True, physics_frequency: float = 600.0, update_fabric: bool = True, disable_physx_fabric_tracker: bool = True, collapse_fixed_joints: bool = False, fix_missing_xform_ops: bool = True, contact_ke: float = 10000.0, contact_kd: float = 100.0, contact_kf: float = 10.0, contact_mu: float = 1.0, contact_ka: float = 0.5, restitution: float = 0.0, contact_margin: float = 0.01, soft_contact_margin: float = 0.01, joint_limit_ke: float = 100.0, joint_limit_kd: float = 1.0, armature: float = 0.1, joint_damping: float = 1.0, pd_scale: float = 1.0, solver_cfg: ~isaacsim.physics.newton.impl.solver_config.NewtonSolverConfig = <factory>, solver_outputs: ~isaacsim.physics.newton.impl.newton_config.NewtonSolverOutputConfig = <factory>, collision_cfg: ~isaacsim.physics.newton.impl.collision_config.CollisionConfig = <factory>, )#

Bases: object

Configuration for Newton physics simulation in Isaac Sim.

This configuration follows IsaacLab’s pattern of separating simulation-level parameters from solver-specific parameters.

armature: float = 0.1#: Default joint armature (rotor inertia).

collapse_fixed_joints: bool = False#

Whether to merge bodies connected by fixed joints during USD parsing.

When enabled, reduces body count and improves performance.

collision_cfg: CollisionConfig#: Collision pipeline configuration, including hydroelastic contact.

contact_ka: float = 0.5#: Default contact adhesion coefficient.

contact_kd: float = 100.0#: Default contact damping coefficient.

contact_ke: float = 10000.0#: Default contact stiffness (spring constant).

contact_kf: float = 10.0#: Default contact friction force coefficient.

contact_margin: float = 0.01#: Contact margin for rigid body collision detection.

contact_mu: float = 1.0#: Default friction coefficient (Coulomb friction).

debug_mode: bool = False#: Whether to enable debug mode for the solver.

disable_physx_fabric_tracker: bool = True#: Whether to pause PhysX fabric change tracking (if PhysX is loaded).

fix_missing_xform_ops: bool = True#: Whether to add missing identity xform operations to geometry prims to suppress USD warnings.

joint_damping: float = 1.0#: Default joint damping coefficient.

joint_limit_kd: float = 1.0#: Default joint limit damping.

joint_limit_ke: float = 100.0#: Default joint limit stiffness.

num_substeps: int = 1#: Number of substeps to use for the solver.

pd_scale: float = 1.0#: Scaling factor for PD controller gains when parsing USD joint drives.

physics_frequency: float = 600.0#: Physics simulation frequency in Hz.

restitution: float = 0.0#: Default coefficient of restitution (bounciness). 0 = no bounce, 1 = perfectly elastic.

soft_contact_margin: float = 0.01#: Contact margin for soft body collision detection.

solver_cfg: NewtonSolverConfig#: Solver-specific configuration.

solver_outputs: NewtonSolverOutputConfig#: Optional solver-computed outputs.

time_step_app: bool = True#

Whether the application should drive simulation time stepping.

If True, the stage update node calls step_sim(). If False, external code must step.

update_fabric: bool = True#: Whether to synchronize Newton state to USD Fabric each frame.

use_cuda_graph: bool = True#

Whether to use CUDA graph capture for performance optimization.

When enabled, the simulation loop is captured as a CUDA graph for faster execution. Highly recommended for production use.

class NewtonSolverOutputConfig( contact_forces: bool = True, link_incoming_joint_force: bool = False, )#

Bases: object

Optional outputs computed by the Newton solver during simulation steps.

Enabling an output can add state storage and per-step computation. Configure the required outputs before initializing physics.

contact_forces: bool = True#: Whether to compute contact forces for contact tensor queries.

link_incoming_joint_force: bool = False#: Whether to compute joint wrenches used by incoming-link and projected-DOF-force queries.

class CollisionConfig( broad_phase: ~typing.Literal['nxn', 'sap', 'explicit'] = 'explicit', rigid_contact_max: int | None = None, hydroelastic: ~isaacsim.physics.newton.impl.collision_config.HydroelasticConfig = <factory>, )#

Bases: object

Configuration for the Newton collision pipeline.

broad_phase: Literal['nxn', 'sap', 'explicit'] = 'explicit'#: Broad-phase pair generation mode.

hydroelastic: HydroelasticConfig#: Hydroelastic contact runtime settings.

rigid_contact_max: int | None = None#

Maximum number of rigid contacts to allocate, or None to derive it from the model.

Must be at least the per-world contact capacity of the solver, such as MuJoCoSolverConfig.nconmax.

class HydroelasticConfig( enabled: bool = True, reduce_contacts: bool = True, buffer_fraction: float = 1.0, buffer_mult_broad: int = 1, buffer_mult_iso: int = 1, buffer_mult_contact: int = 1, normal_matching: bool = True, anchor_contact: bool = False, margin_contact_area: float = 0.01, output_contact_surface: bool = False, mc_edge_clamp_min: float = 0.02, )#

Bases: object

Runtime configuration for hydroelastic contact.

Per-shape opt-in (enable, stiffness, SDF resolution) is authored in USD via NewtonSDFCollisionAPI and parsed automatically.

anchor_contact: bool = False#: Add an extra contact at the center of pressure per normal bin.

buffer_fraction: float = 1.0#

(0, 1].

Type:: GPU buffer size relative to the worst-case estimate. Range

buffer_mult_broad: int = 1#

Multiplier for the broad-phase block pair buffer, applied after buffer_fraction.

Increase when a broad phase overflow warning is reported.

buffer_mult_contact: int = 1#

Multiplier for the face contact buffer, applied after buffer_fraction.

Increase when a face contact overflow warning is reported.

buffer_mult_iso: int = 1#

Multiplier for the iso-surface extraction buffers, applied after buffer_fraction.

Increase when an iso subblock or iso voxel overflow warning is reported.

enabled: bool = True#: Whether to run the hydroelastic contact path when hydroelastic shapes are present.

margin_contact_area: float = 0.01#: Area used for non-penetrating margin contacts [m²].

mc_edge_clamp_min: float = 0.02#: Marching-cubes edge clamp parameter.

normal_matching: bool = True#: Align reduced contact normals with the aggregate force direction.

output_contact_surface: bool = False#: Export contact patch triangles for visualization.

reduce_contacts: bool = True#: Merge patch triangles into fewer representative contacts.

class XPBDSolverConfig( solver_type: Literal['xpbd'] = 'xpbd', iterations: int = 2, )#

Bases: NewtonSolverConfig

Configuration for XPBD (Extended Position-Based Dynamics) solver.

An implicit integrator using eXtended Position-Based Dynamics (XPBD) for rigid and soft body simulation.

References

Miles Macklin, Matthias Müller, and Nuttapong Chentanez. 2016. XPBD: position-based simulation of compliant constrained dynamics. In Proceedings of the 9th International Conference on Motion in Games (MIG ‘16). Association for Computing Machinery, New York, NY, USA, 49-54. https://doi.org/10.1145/2994258.2994272
Matthias Müller, Miles Macklin, Nuttapong Chentanez, Stefan Jeschke, and Tae-Yong Kim. 2020. Detailed rigid body simulation with extended position based dynamics. In Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation (SCA ‘20). Eurographics Association, Goslar, DEU, Article 10, 1-12. https://doi.org/10.1111/cgf.14105

iterations: int = 2#: Number of solver iterations.

solver_type: Literal['xpbd'] = 'xpbd'#

‘xpbd’, ‘mujoco’, ‘featherstone’, ‘semiImplicit’, ‘vbd’.

Type:: Type of solver to use

class MuJoCoSolverConfig( solver_type: Literal['mujoco'] = 'mujoco', njmax: int = 1200, nconmax: int | None = 200, cone: Literal['pyramidal', 'elliptic'] | None = None, use_mujoco_cpu: bool = False, disable_contacts: bool = False, update_data_interval: int = 1, save_to_mjcf: str | None = None, use_mujoco_contacts: bool = False, include_sites: bool = False, )#

Bases: NewtonSolverConfig

Configuration for MuJoCo Warp solver-related parameters.

These parameters are used to configure the MuJoCo Warp solver. For more information, see the MuJoCo Warp documentation.

cone: Literal['pyramidal', 'elliptic'] | None = None#: Contact friction cone override. If None, use the value authored on the physics scene.

disable_contacts: bool = False#: Whether to disable contact computation in MuJoCo.

include_sites: bool = False#: If True, Newton shapes marked with ShapeFlags.SITE are exported as MuJoCo sites.

nconmax: int | None = 200#: Number of contact points per environment (world).

njmax: int = 1200#: Number of constraints per environment (world).

save_to_mjcf: str | None = None#: Optional path to save the generated MJCF model file.

solver_type: Literal['mujoco'] = 'mujoco'#

‘xpbd’, ‘mujoco’, ‘featherstone’, ‘semiImplicit’, ‘vbd’.

Type:: Type of solver to use

update_data_interval: int = 1#: Frequency (in simulation steps) at which to update the MuJoCo Data object from the Newton state.

use_mujoco_contacts: bool = False#: Whether to use MuJoCo’s contact computation.

use_mujoco_cpu: bool = False#: Whether to use the pure MuJoCo backend instead of mujoco_warp.