isaaclab.sim.schemas

Sub-module containing utilities for schemas used in Omniverse.

We wrap the USD schemas for PhysX and USD Physics in a more convenient API for setting the parameters from Python. This is done so that configuration objects can define the schema properties to set and make it easier to tune the physics parameters without requiring to open Omniverse Kit and manually set the parameters into the respective USD attributes.

Caution

Schema properties cannot be applied on prims that are prototypes as they are read-only prims. This particularly affects instanced assets where some of the prims (usually the visual and collision meshes) are prototypes so that the instancing can be done efficiently.

In such cases, it is assumed that the prototypes have sim-ready properties on them that don’t need to be modified. Trying to set properties into prototypes will throw a warning saying that the prim is a prototype and the properties cannot be set.

The schemas are defined in the following links:

• UsdPhysics schema

• PhysxSchema schema

Locally, the schemas are defined in the following files:

• _isaac_sim/extsPhysics/omni.usd.schema.physics/plugins/UsdPhysics/resources/UsdPhysics/schema.usda

• _isaac_sim/extsPhysics/omni.usd.schema.physx/plugins/PhysxSchema/resources/generatedSchema.usda

Solver-common base classes

These base classes carry the universal-physics fields that every backend honors. They live in core isaaclab and have no backend dependency. For backend-specific knobs, use the matching subclass in isaaclab_physx.sim.schemas or isaaclab_newton.sim.schemas. See Schema Configuration Classes for the full design.

ArticulationRootBaseCfg	Solver-common properties to apply to the root of an articulation.
RigidBodyBaseCfg	Solver-common properties to apply to a rigid body.
CollisionBaseCfg	Solver-common properties to apply to colliders.
JointDriveBaseCfg	Solver-common properties to define the drive mechanism of a joint.
MeshCollisionBaseCfg	Solver-common properties to apply to a mesh in regards to collision.
MassPropertiesCfg	Properties to define explicit mass properties of a rigid body.
JointDrivePropertiesCfg	Deprecated: use PhysxJointDrivePropertiesCfg or JointDriveBaseCfg.
FixedTendonPropertiesCfg	Deprecated: use PhysxFixedTendonPropertiesCfg.
DeformableBodyPropertiesBaseCfg	Base deformable body properties for backend-specific extensions.

Mesh collision approximations (USD-only, no PhysX schema)

BoundingCubePropertiesCfg	Bounding-cube mesh collision approximation.
BoundingSpherePropertiesCfg	Bounding-sphere mesh collision approximation.

Functions

define_articulation_root_properties(...[, stage])	Apply the articulation root schema on the input prim and set its properties.
modify_articulation_root_properties(...[, stage])	Modify PhysX parameters for an articulation root prim.
define_rigid_body_properties(prim_path, cfg)	Apply the rigid body schema on the input prim and set its properties.
modify_rigid_body_properties(prim_path, cfg)	Modify parameters for a rigid body prim.
activate_contact_sensors(prim_path[, ...])	Activate the contact sensor on all rigid bodies under a specified prim path.
define_collision_properties(prim_path, cfg)	Apply the collision schema on the input prim and set its properties.
modify_collision_properties(prim_path, cfg)	Modify PhysX properties of collider prim.
define_mass_properties(prim_path, cfg[, stage])	Apply the mass schema on the input prim and set its properties.
modify_mass_properties(prim_path, cfg[, stage])	Set properties for the mass of a rigid body prim.
modify_joint_drive_properties(prim_path, cfg)	Modify parameters for a joint prim.
define_mesh_collision_properties(prim_path, cfg)	Apply the mesh collision schema on the input prim and set its properties.
modify_mesh_collision_properties(prim_path, cfg)	Set properties for the mesh collision of a prim.
modify_fixed_tendon_properties(prim_path, cfg)	Modify PhysX parameters for a fixed tendon attachment prim.
define_deformable_body_properties(prim_path, cfg)	Apply the deformable body schema on the input prim and set its properties.
modify_deformable_body_properties(prim_path, cfg)	Modify deformable body parameters for a deformable body prim.

Articulation Root

class isaaclab.sim.schemas.ArticulationRootBaseCfg

Solver-common properties to apply to the root of an articulation.

Carries fix_root_link (writer-side; materializes a UsdPhysics.FixedJoint between the world frame and the root link) and articulation_enabled whose only USD path today is the PhysX-namespaced physxArticulation:articulationEnabled attribute. The base class itself declares no USD namespace; the writer consults _usd_field_exceptions to route articulation_enabled to its non-base namespace and apply PhysxArticulationAPI only when the user authored that one field. For PhysX-only articulation-root properties (self-collisions, TGS solver iterations, sleep / stabilization thresholds), use PhysxArticulationRootPropertiesCfg.

See modify_articulation_root_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.

Attributes:

articulation_enabled	Whether to enable or disable the articulation.
fix_root_link	Whether to fix the root link of the articulation.

articulation_enabled: bool | None

Whether to enable or disable the articulation.

PhysX honors this per-articulation at sim time via physxArticulation:articulationEnabled: setting False makes PhysX skip the articulation in its solver passes.

On Newton, the field is read by the IsaacLab Newton wrapper at spawn time (isaaclab_newton/assets/rigid_object/rigid_object.py:1035) as a guard against accidentally spawning a RigidObject over a prim that still has ArticulationRootAPI applied; setting False suppresses the guard error. The Newton solver itself does not consult the flag at sim time.

Placed on the solver-common class because the user-facing intent is universal and both PhysX (sim-time) and the IL Newton wrapper (spawn-time) honor it.

fix_root_link: bool | None

Whether to fix the root link of the articulation.

• If set to None, the root link is not modified.

• If the articulation already has a fixed root link, this flag will enable or disable the fixed joint.

• If the articulation does not have a fixed root link, this flag will create a fixed joint between the world frame and the root link. The joint is created with the name “FixedJoint” under the articulation prim.

Note

This is a non-USD schema property. It is handled by the modify_articulation_root_properties() function.

isaaclab.sim.schemas.define_articulation_root_properties(prim_path: str, cfg: schemas_cfg.ArticulationRootBaseCfg, stage: Usd.Stage | None = None)

Apply the articulation root schema on the input prim and set its properties.

See modify_articulation_root_properties() for more details on how the properties are set.

Parameters:

• prim_path – The prim path where to apply the articulation root schema.

• cfg – The configuration for the articulation root.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

• ValueError – When the prim path is not valid.

• TypeError – When the prim already has conflicting API schemas.

isaaclab.sim.schemas.modify_articulation_root_properties(prim_path: str, cfg: schemas_cfg.ArticulationRootBaseCfg, stage: Usd.Stage | None = None) → bool

Modify PhysX parameters for an articulation root prim.

The articulation root marks the root of an articulation tree. For floating articulations, this should be on the root body. For fixed articulations, this API can be on a direct or indirect parent of the root joint which is fixed to the world.

The schema comprises of attributes that belong to the ArticulationRootAPI and PhysxArticulationAPI. schemas. The latter contains the PhysX parameters for the articulation root.

The properties are applied to the articulation root prim. The common properties (such as solver position and velocity iteration counts, sleep threshold, stabilization threshold) take precedence over those specified in the rigid body schemas for all the rigid bodies in the articulation.

Caution

When the attribute schemas_cfg.ArticulationRootPropertiesCfg.fix_root_link is set to True, a fixed joint is created between the root link and the world frame (if it does not already exist). However, to deal with physics parser limitations, the articulation root schema needs to be applied to the parent of the root link.

Note

This function is decorated with apply_nested() that set the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path to the articulation root.

• cfg – The configuration for the articulation root.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Raises:

NotImplementedError – When the root prim is not a rigid body and a fixed joint is to be created.

For PhysX-specific articulation properties (self-collisions, TGS solver iterations, sleep/stabilization thresholds), see PhysxArticulationRootPropertiesCfg. For Newton-native self-collisions, see NewtonArticulationRootPropertiesCfg.

Rigid Body

class isaaclab.sim.schemas.RigidBodyBaseCfg

Solver-common properties to apply to a rigid body.

Contains properties from the UsdPhysics.RigidBodyAPI that are common across all simulation backends, plus disable_gravity whose USD attribute today is PhysX-namespaced but whose semantics (per-body gravity exclusion) are universal: PhysX honors it per-body; Newton’s importer consumes it at the scene level (partial honor, documented on the field). For PhysX-only rigid-body properties, use PhysxRigidBodyPropertiesCfg.

See 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.

Attributes:

rigid_body_enabled	Whether to enable or disable the rigid body.
kinematic_enabled	Determines whether the body is kinematic or not.
disable_gravity	Disable gravity for the body.

rigid_body_enabled: bool | None

Whether to enable or disable the rigid body.

kinematic_enabled: bool | None

Determines whether the body is kinematic or not.

A kinematic body is a body that is moved through animated poses or through user defined poses. The simulation still derives velocities for the kinematic body based on the external motion.

For more information on kinematic bodies, please refer to the documentation.

disable_gravity: bool | None

Disable gravity for the body.

PhysX honors this per-body via physxRigidBody:disableGravity: setting True excludes the body from world gravity integration.

Newton currently consumes the same USD attribute at the scene level – Newton’s importer reads physxRigidBody:disableGravity on the scene prim and uses it to drive the scene-wide builder.gravity flag (import_usd.py:1212). Per-body intent is therefore partially honored on Newton: whichever rigid body has the attribute authored ends up controlling scene-wide gravity, and other bodies cannot be selectively excluded.

The field is placed on the base because the user-facing intent (per-body gravity exclusion for markers, sensors, kinematic targets) is universal physics and PhysX honors it fully. Closing the Newton gap is a kernel-level fix (introduce Model.body_disable_gravity boolean array consumed by the integrator) that does not require a cfg-API change.

isaaclab.sim.schemas.define_rigid_body_properties(prim_path: str, cfg: schemas_cfg.RigidBodyBaseCfg, stage: Usd.Stage | None = None)

Apply the rigid body schema on the input prim and set its properties.

See modify_rigid_body_properties() for more details on how the properties are set.

Parameters:

• prim_path – The prim path where to apply the rigid body schema.

• cfg – The configuration for the rigid body.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

• ValueError – When the prim path is not valid.

• TypeError – When the prim already has conflicting API schemas.

isaaclab.sim.schemas.modify_rigid_body_properties(prim_path: str, cfg: schemas_cfg.RigidBodyBaseCfg, stage: Usd.Stage | None = None) → bool

Modify parameters for a rigid body prim.

A rigid body is a single body that can be simulated by a physics engine. It can be either dynamic or kinematic. A dynamic body responds to forces and collisions. A kinematic body can be moved by the user, but does not respond to forces.

Solver-common properties (from RigidBodyAPI) are always written. Solver-specific properties are written based on the cfg subclass metadata (_usd_namespace, _usd_applied_schema).

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path to the rigid body.

• cfg – The configuration for the rigid body. Accepts RigidBodyBaseCfg for solver-common properties, PhysxRigidBodyPropertiesCfg for PhysX properties, or MujocoRigidBodyPropertiesCfg for Newton (MuJoCo) properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

isaaclab.sim.schemas.activate_contact_sensors(prim_path: str, threshold: float = 0.0, stage: pxr.Usd.Stage = None)

Activate the contact sensor on all rigid bodies under a specified prim path.

This function adds the PhysX contact report API to all rigid bodies under the specified prim path. It also sets the force threshold beyond which the contact sensor reports the contact. The contact reporting API can only be added to rigid bodies.

Parameters:

• prim_path – The prim path under which to search and prepare contact sensors.

• threshold – The threshold for the contact sensor. Defaults to 0.0.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

• ValueError – If the input prim path is not valid.

• ValueError – If there are no rigid bodies under the prim path.

For PhysX-specific rigid body properties (damping, max velocities, solver iterations, sleep/stabilization), see PhysxRigidBodyPropertiesCfg. For MuJoCo-specific gravity compensation, see MujocoRigidBodyPropertiesCfg.

Collision

class isaaclab.sim.schemas.CollisionBaseCfg

Solver-common properties to apply to colliders.

Contains collision_enabled from the UsdPhysics.CollisionAPI and the contact_offset / rest_offset knobs whose USD attributes today are PhysX-namespaced (physxCollision:contactOffset, physxCollision:restOffset) but whose semantics (collision-pair generation distance, rest separation gap) are universal physics: PhysX consumes them natively, Newton’s importer consumes them via the PhysX bridge resolver and populates Model.shape_collision_radius / Model.shape_collision_thickness from the gap and margin keys (see import_usd.py:2104, 2111). For PhysX-only collision properties (e.g. torsional patch friction), use PhysxCollisionPropertiesCfg.

See modify_collision_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.

Attributes:

collision_enabled	Whether to enable or disable collisions.
contact_offset	Contact offset for the collision shape [m].
rest_offset	Rest offset for the collision shape [m].

collision_enabled: bool | None

Whether to enable or disable collisions.

Writes physics:collisionEnabled via UsdPhysics.CollisionAPI.

contact_offset: float | None

Contact offset for the collision shape [m].

The collision detector generates contact points as soon as two shapes get closer than the sum of their contact offsets. This quantity should be non-negative which means that contact generation can potentially start before the shapes actually penetrate.

Writes physxCollision:contactOffset. Newton’s USD importer consumes the same attribute via its PhysX-bridge resolver.

rest_offset: float | None

Rest offset for the collision shape [m].

The rest offset quantifies how close a shape gets to others at rest, At rest, the distance between two vertically stacked objects is the sum of their rest offsets. If a pair of shapes have a positive rest offset, the shapes will be separated at rest by an air gap.

Writes physxCollision:restOffset. Newton’s USD importer consumes the same attribute via its PhysX-bridge resolver.

isaaclab.sim.schemas.define_collision_properties(prim_path: str, cfg: schemas_cfg.CollisionPropertiesCfg, stage: Usd.Stage | None = None)

Apply the collision schema on the input prim and set its properties.

See modify_collision_properties() for more details on how the properties are set.

Parameters:

• prim_path – The prim path where to apply the rigid body schema.

• cfg – The configuration for the collider.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

ValueError – When the prim path is not valid.

isaaclab.sim.schemas.modify_collision_properties(prim_path: str, cfg: schemas_cfg.CollisionPropertiesCfg, stage: Usd.Stage | None = None) → bool

Modify PhysX properties of collider prim.

These properties are based on the UsdPhysics.CollisionAPI and PhysxSchema.PhysxCollisionAPI schemas. For more information on the properties, please refer to the official documentation.

Tuning these parameters influence the contact behavior of the rigid body. For more information on tune them and their effect on the simulation, please refer to the PhysX documentation.

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path of parent.

• cfg – The configuration for the collider.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

For PhysX torsional patch friction, see PhysxCollisionPropertiesCfg. For Newton-native contact margin/gap, see NewtonCollisionPropertiesCfg.

Mass

class isaaclab.sim.schemas.MassPropertiesCfg

Properties to define explicit mass properties of a rigid body.

See modify_mass_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.

Attributes:

mass	The mass of the rigid body (in kg).
density	The density of the rigid body (in kg/m^3).

mass: float | None

The mass of the rigid body (in kg).

Note

If non-zero, the mass is ignored and the density is used to compute the mass.

density: float | None

The density of the rigid body (in kg/m^3).

The density indirectly defines the mass of the rigid body. It is generally computed using the collision approximation of the body.

isaaclab.sim.schemas.define_mass_properties(prim_path: str, cfg: schemas_cfg.MassPropertiesCfg, stage: Usd.Stage | None = None)

Apply the mass schema on the input prim and set its properties.

See modify_mass_properties() for more details on how the properties are set.

Parameters:

• prim_path – The prim path where to apply the rigid body schema.

• cfg – The configuration for the mass properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

ValueError – When the prim path is not valid.

isaaclab.sim.schemas.modify_mass_properties(prim_path: str, cfg: schemas_cfg.MassPropertiesCfg, stage: Usd.Stage | None = None) → bool

Set properties for the mass of a rigid body prim.

These properties are based on the UsdPhysics.MassAPI schema. If the mass is not defined, the density is used to compute the mass. However, in that case, a collision approximation of the rigid body is used to compute the density. For more information on the properties, please refer to the documentation.

Caution

The mass of an object can be specified in multiple ways and have several conflicting settings that are resolved based on precedence. Please make sure to understand the precedence rules before using this property.

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path of the rigid body.

• cfg – The configuration for the mass properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Joint Drive

class isaaclab.sim.schemas.JointDriveBaseCfg

Solver-common properties to define the drive mechanism of a joint.

Contains properties from the UsdPhysics.DriveAPI that are common across all simulation backends, plus max_joint_velocity whose USD attribute today is PhysX-namespaced but whose semantics (per-DOF velocity limit) are universal: Newton’s importer consumes physxJoint:maxJointVelocity and populates Model.joint_velocity_limit; PhysX consumes it natively. For PhysX-only drive properties, use PhysxJointDrivePropertiesCfg.

See 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.

Attributes:

drive_type	Joint drive type to apply.
max_force	Maximum force/torque that can be applied to the joint [N for linear joints, N-m for angular joints].
max_effort	Deprecated alias for max_force.
stiffness	Stiffness of the joint drive.
damping	Damping of the joint drive.
ensure_drives_exist	If True, ensure every joint has a non-zero drive so that physics backends (e.g. Newton) create proper actuators for it.
max_joint_velocity	Maximum velocity of the joint [m/s for linear joints, rad/s for angular joints].
max_velocity	Deprecated alias for max_joint_velocity.

drive_type: Literal['force', 'acceleration'] | None

Joint drive type to apply.

If the drive type is “force”, then the joint is driven by a force. If the drive type is “acceleration”, then the joint is driven by an acceleration (usually used for kinematic joints).

max_force: float | None

Maximum force/torque that can be applied to the joint [N for linear joints, N-m for angular joints].

Writes drive:<linear|angular>:physics:maxForce via UsdPhysics.DriveAPI.

max_effort: float | None

Deprecated alias for max_force.

Deprecated since version 4.6.25: Use max_force instead. The cfg field is renamed so its snake_case name maps identity-style to the USD camelCase attribute (maxForce on UsdPhysics.DriveAPI). The alias is forwarded to max_force in __post_init__() and will be removed in 4.0.

stiffness: float | None

Stiffness of the joint drive.

The unit depends on the joint model:

• For linear joints, the unit is kg-m/s^2 (N/m).

• For angular joints, the unit is kg-m^2/s^2/rad (N-m/rad).

damping: float | None

Damping of the joint drive.

The unit depends on the joint model:

• For linear joints, the unit is kg-m/s (N-s/m).

• For angular joints, the unit is kg-m^2/s/rad (N-m-s/rad).

ensure_drives_exist: bool

If True, ensure every joint has a non-zero drive so that physics backends (e.g. Newton) create proper actuators for it.

When a USD asset defines PhysicsDriveAPI with stiffness=0 and damping=0, some backends treat the joint as passive (no PD control). Enabling this flag writes a minimal stiffness (1e-3) to any drive whose stiffness and damping are both zero, guaranteeing that the backend recognises the drive as active. The actual gains are expected to be overridden later by the actuator model.

max_joint_velocity: float | None

Maximum velocity of the joint [m/s for linear joints, rad/s for angular joints].

Notes

Today this writes physxJoint:maxJointVelocity (a PhysX add-on schema attribute). Newton’s USD importer consumes the same attribute via its PhysX-bridge resolver and populates Model.joint_velocity_limit; the PhysX engine consumes it natively. The Kamino solver honors the limit at the simulation step. The XPBD, Featherstone, and Semi-implicit Newton solvers import the value but do not consume it in their kernels; the MuJoCo (MJC) solver explicitly drops it. When Newton ships newton:maxJointVelocity as a registered applied API, the writer namespace will switch transparently and this docstring caveat will be removed.

max_velocity: float | None

Deprecated alias for max_joint_velocity.

Deprecated since version 4.6.25: Use max_joint_velocity instead. The cfg field is renamed so its snake_case name maps identity-style to the USD camelCase attribute (physxJoint:maxJointVelocity). The alias is forwarded to max_joint_velocity in __post_init__() and will be removed in 4.0.

isaaclab.sim.schemas.modify_joint_drive_properties(prim_path: str, cfg: schemas_cfg.JointDriveBaseCfg, stage: Usd.Stage | None = None) → bool

Modify parameters for a joint prim.

This function checks if the input prim is a prismatic or revolute joint and applies the joint drive schema on it. If the joint is a tendon (i.e., it has the PhysxTendonAxisAPI schema applied on it), then the joint drive schema is not applied.

Solver-common properties (from UsdPhysics.DriveAPI) are always written. Solver-specific properties are written based on the cfg subclass metadata (_usd_namespace, _usd_applied_schema).

Caution

We highly recommend modifying joint properties of articulations through the functionalities in the isaaclab.actuators module. The methods here are for setting simulation low-level properties only.

Parameters:

• prim_path – The prim path where to apply the joint drive schema.

• cfg – The configuration for the joint drive. Accepts JointDriveBaseCfg for solver-common properties, PhysxJointDrivePropertiesCfg for PhysX properties, or MujocoJointDrivePropertiesCfg for Newton (MuJoCo) properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Raises:

ValueError – If the input prim path is not valid.

For PhysX-specific drive properties, see PhysxJointDrivePropertiesCfg. For MuJoCo actuator gravity compensation, see MujocoJointDrivePropertiesCfg.

Mesh Collision

class isaaclab.sim.schemas.MeshCollisionBaseCfg

Solver-common properties to apply to a mesh in regards to collision.

Carries only the standard UsdPhysics:MeshCollisionAPI token (mesh_approximation_name -> physics:approximation). For PhysX-cooking tunables (convex hull / decomposition / triangle mesh / SDF), use the Physx*PropertiesCfg subclasses in isaaclab_physx.sim.schemas.

See modify_mesh_collision_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.

Attributes:

mesh_approximation_name

"none".

mesh_approximation_name: str

“none”.

Writes physics:approximation via UsdPhysics.MeshCollisionAPI. Refer to schemas.MESH_APPROXIMATION_TOKENS for available options.

Type:

Name of mesh collision approximation method. Default

class isaaclab.sim.schemas.BoundingCubePropertiesCfg

Bases: MeshCollisionBaseCfg

Bounding-cube mesh collision approximation. USD-only; authors no PhysX schema.

Writes the boundingCube token to physics:approximation via UsdPhysics.MeshCollisionAPI.

Original USD Documentation: https://docs.omniverse.nvidia.com/kit/docs/omni_usd_schema_physics/latest/class_usd_physics_mesh_collision_a_p_i.html

Attributes:

mesh_approximation_name

"boundingCube".

mesh_approximation_name: str

“boundingCube”.

Type:

Name of mesh collision approximation method. Default

class isaaclab.sim.schemas.BoundingSpherePropertiesCfg

Bases: MeshCollisionBaseCfg

Bounding-sphere mesh collision approximation. USD-only; authors no PhysX schema.

Writes the boundingSphere token to physics:approximation via UsdPhysics.MeshCollisionAPI.

Original USD Documentation: https://docs.omniverse.nvidia.com/kit/docs/omni_usd_schema_physics/latest/class_usd_physics_mesh_collision_a_p_i.html

Attributes:

mesh_approximation_name

"boundingSphere".

mesh_approximation_name: str

“boundingSphere”.

Type:

Name of mesh collision approximation method. Default

isaaclab.sim.schemas.define_mesh_collision_properties(prim_path: str, cfg: schemas_cfg.MeshCollisionBaseCfg, stage: Usd.Stage | None = None)

Apply the mesh collision schema on the input prim and set its properties.

See modify_mesh_collision_properties() for more details on how the properties are set.

Parameters:

• prim_path – The prim path where to apply the mesh collision schema.

• cfg – The configuration for the mesh collision properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Raises:

ValueError – When the prim path is not valid.

isaaclab.sim.schemas.modify_mesh_collision_properties(prim_path: str, cfg: schemas_cfg.MeshCollisionBaseCfg, stage: Usd.Stage | None = None) → bool

Set properties for the mesh collision of a prim.

Metadata-driven writer. The standard UsdPhysics.MeshCollisionAPI is applied unconditionally (it is the carrier of the physics:approximation token). The PhysX cooking schema declared by _usd_applied_schema (e.g. PhysxConvexHullCollisionAPI) is gated on the user authoring at least one non-None namespaced tuning field, mirroring the gating used by the other consumption-gated writers (rigid body, joint drive, collision, articulation root).

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path of the rigid body. This prim should be a Mesh prim.

• cfg – The configuration for the mesh collision properties.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Raises:

ValueError – When the mesh approximation name is invalid.

For PhysX cooking schemas (convex hull / decomposition / triangle mesh / SDF), see the Physx*PropertiesCfg family in isaaclab_physx.sim.schemas. For Newton hull-vertex limit, see NewtonMeshCollisionPropertiesCfg.

Tendon

isaaclab.sim.schemas.modify_fixed_tendon_properties(prim_path: str, cfg: schemas_cfg.PhysxFixedTendonPropertiesCfg, stage: Usd.Stage | None = None) → bool

Modify PhysX parameters for a fixed tendon attachment prim.

A fixed tendon can be used to link multiple degrees of freedom of articulation joints through length and limit constraints. For instance, it can be used to set up an equality constraint between a driven and passive revolute joints.

The schema comprises of attributes that belong to the PhysxTendonAxisRootAPI schema.

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path to the tendon attachment.

• cfg – The configuration for the tendon attachment.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Raises:

ValueError – If the input prim path is not valid.

isaaclab.sim.schemas.modify_spatial_tendon_properties(prim_path: str, cfg: schemas_cfg.PhysxSpatialTendonPropertiesCfg, stage: Usd.Stage | None = None) → bool

Modify PhysX parameters for a spatial tendon attachment prim.

A spatial tendon can be used to link multiple degrees of freedom of articulation joints through length and limit constraints. For instance, it can be used to set up an equality constraint between a driven and passive revolute joints.

The schema comprises of attributes that belong to the PhysxTendonAxisRootAPI schema.

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path to the tendon attachment.

• cfg – The configuration for the tendon attachment.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.

Raises:

ValueError – If the input prim path is not valid.

Tendon cfg classes are PhysX-only and live in isaaclab_physx.sim.schemas (PhysxFixedTendonPropertiesCfg, PhysxSpatialTendonPropertiesCfg).

Deformable Body

class isaaclab.sim.schemas.DeformableBodyPropertiesBaseCfg

Bases: object

Base deformable body properties for backend-specific extensions.

This class is currently empty. It will be populated once the USD deformable schemas can be unified more cleanly between physics backends.

isaaclab.sim.schemas.define_deformable_body_properties(prim_path: str, cfg: schemas_cfg.DeformableBodyPropertiesBaseCfg, stage: Usd.Stage | None = None, deformable_type: str = 'volume', sim_mesh_prim_path: str | None = None)

Apply the deformable body schema on the input prim and set its properties. The input prim should have a visual surface mesh as child. Volume deformables will have their simulation tetrahedral mesh automatically computed from the surface mesh of the input prim. Surface deformables simply copy the visual mesh as simulation mesh.

See modify_deformable_body_properties() for more details on how the properties are set.

Note

If the input prim is not a mesh, this function will traverse the prim and find the first mesh under it. If no mesh or multiple meshes are found, an error is raised. This is because the deformable body schema can only be applied to a single mesh.

Parameters:

• prim_path – The prim path where to apply the deformable body schema.

• cfg – The configuration for the deformable body.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

• deformable_type – The type of the deformable body (surface or volume). This is used to determine which USD API to use for the deformable body. Defaults to “volume”.

• sim_mesh_prim_path – Optional override for the simulation mesh creation prim path. Ignored when pre-tetrahedralized mesh is found for volume deformables. If None, it is set to {prim_path}/sim_mesh.

Raises:

• ValueError – When the prim path is not valid.

• ValueError – When the prim has no mesh or multiple meshes.

• RuntimeError – When setting the deformable body properties fails.

isaaclab.sim.schemas.modify_deformable_body_properties(prim_path: str, cfg: schemas_cfg.DeformableBodyPropertiesBaseCfg, stage: Usd.Stage | None = None)

Modify deformable body parameters for a deformable body prim.

A deformable body is a single body (either surface or volume deformable) that can be simulated by PhysX or Newton. Unlike rigid bodies, deformable bodies support relative motion of the nodes in the mesh. Consequently, they can be used to simulate deformations under applied forces.

PhysX deformable body simulation employs Finite Element Analysis (FEA) to simulate the deformations of the mesh. It uses two meshes to represent the deformable body:

1. Simulation mesh: This mesh is used for the simulation and is the one that is deformed by the solver.

2. Collision mesh: This mesh only needs to match the surface of the simulation mesh and is used for collision detection.

For most applications, we assume that the above two meshes are computed from the “render mesh” of the deformable body. The render mesh is the mesh that is visible in the scene and is used for rendering purposes. It is composed of triangles, while the simulation mesh is composed of tetrahedrons for volume deformables, and triangles for surface deformables.

We apply similar design choices to the simulation in Newton with a separate visual, simulation and collision mesh.

Caution

The deformable body schema is still under development by the Omniverse team. The current implementation works with the PhysX schemas shipped with Isaac Sim 6.0.0 onwards. It may change in future releases.

Note

This function is decorated with apply_nested() that sets the properties to all the prims (that have the schema applied on them) under the input prim path.

Parameters:

• prim_path – The prim path to the deformable body.

• cfg – The configuration for the deformable body.

• stage – The stage where to find the prim. Defaults to None, in which case the current stage is used.

Returns:

True if the properties were successfully set, False otherwise.