isaaclab.sim.converters

Sub-module containing converters for converting various file types to USD.

In order to support direct loading of various file types into Omniverse, we provide a set of converters that can convert the file into a USD file. The converters are implemented as sub-classes of the AssetConverterBase class.

The following converters are currently supported:

• UrdfConverter: Converts a URDF file into a USD file.

• MeshConverter: Converts a mesh file into a USD file. This supports OBJ, STL and FBX files.

Classes

AssetConverterBase	Base class for converting an asset file from different formats into USD format.
AssetConverterBaseCfg	The base configuration class for asset converters.
MeshConverter	Converter for a mesh file in OBJ / STL / FBX format to a USD file.
MeshConverterCfg	The configuration class for MeshConverter.
UrdfConverter	Converter for a URDF description file to a USD file.
UrdfConverterCfg	The configuration class for UrdfConverter.
MjcfConverter	Converter for a MJCF description file to a USD file.
MjcfConverterCfg	The configuration class for MjcfConverter.

Asset Converter Base

class isaaclab.sim.converters.AssetConverterBase

Base class for converting an asset file from different formats into USD format.

This class provides a common interface for converting an asset file into USD. It does not provide any implementation for the conversion. The derived classes must implement the _convert_asset() method to provide the actual conversion.

The file conversion is lazy if the output directory (AssetConverterBaseCfg.usd_dir) is provided. In the lazy conversion, the USD file is re-generated only if:

• The asset file is modified.

• The configuration parameters are modified.

• The USD file does not exist.

To override this behavior to force conversion, the flag AssetConverterBaseCfg.force_usd_conversion can be set to True.

When no output directory is defined, lazy conversion is deactivated and the generated USD file is stored in folder /tmp/IsaacLab/usd_{date}_{time}_{random}, where the parameters in braces are generated at runtime. The random identifiers help avoid a race condition where two simultaneously triggered conversions try to use the same directory for reading/writing the generated files.

Note

Changes to the parameters AssetConverterBaseCfg.asset_path, AssetConverterBaseCfg.usd_dir, and AssetConverterBaseCfg.usd_file_name are not considered as modifications in the configuration instance that trigger the USD file re-generation.

Methods:

__init__(cfg)

Initializes the class.

Attributes:

usd_dir	The absolute path to the directory where the generated USD files are stored.
usd_file_name	The file name of the generated USD file.
usd_path	The absolute path to the generated USD file.
usd_instanceable_meshes_path	The relative path to the USD file with meshes.

__init__(cfg: AssetConverterBaseCfg)

Initializes the class.

Parameters:

cfg – The configuration instance for converting an asset file to USD format.

Raises:

ValueError – When provided asset file does not exist.

property usd_dir: str

The absolute path to the directory where the generated USD files are stored.

property usd_file_name: str

The file name of the generated USD file.

property usd_path: str

The absolute path to the generated USD file.

property usd_instanceable_meshes_path: str

The relative path to the USD file with meshes.

The path is with respect to the USD directory usd_dir. This is to ensure that the mesh references in the generated USD file are resolved relatively. Otherwise, it becomes difficult to move the USD asset to a different location.

class isaaclab.sim.converters.AssetConverterBaseCfg

The base configuration class for asset converters.

Attributes:

asset_path	The absolute path to the asset file to convert into USD.
usd_dir	The output directory path to store the generated USD file.
usd_file_name	The name of the generated usd file.
force_usd_conversion	Force the conversion of the asset file to usd.
make_instanceable	Make the generated USD file instanceable.

asset_path: str

The absolute path to the asset file to convert into USD.

usd_dir: str | None

The output directory path to store the generated USD file. Defaults to None.

If None, it is resolved as /tmp/IsaacLab/usd_{date}_{time}_{random}, where the parameters in braces are runtime generated.

usd_file_name: str | None

The name of the generated usd file. Defaults to None.

If None, it is resolved from the asset file name. For example, if the asset file name is "my_asset.urdf", then the generated USD file name is "my_asset.usd".

If the providing file name does not end with “.usd” or “.usda”, then the extension “.usd” is appended to the file name.

force_usd_conversion: bool

Force the conversion of the asset file to usd. Defaults to False.

If True, then the USD file is always generated. It will overwrite the existing USD file if it exists.

make_instanceable: bool

Make the generated USD file instanceable. Defaults to True.

Note

Instancing helps reduce the memory footprint of the asset when multiple copies of the asset are used in the scene. For more information, please check the USD documentation on scene-graph instancing.

Mesh Converter

class isaaclab.sim.converters.MeshConverter

Bases: AssetConverterBase

Converter for a mesh file in OBJ / STL / FBX format to a USD file.

This class wraps around the omni.kit.asset_converter extension to provide a lazy implementation for mesh to USD conversion. It stores the output USD file in an instanceable format since that is what is typically used in all learning related applications.

To make the asset instanceable, we must follow a certain structure dictated by how USD scene-graph instancing and physics work. The rigid body component must be added to each instance and not the referenced asset (i.e. the prototype prim itself). This is because the rigid body component defines properties that are specific to each instance and cannot be shared under the referenced asset. For more information, please check the documentation.

Due to the above, we follow the following structure:

• {prim_path} - The root prim that is an Xform with the rigid body and mass APIs if configured.

• {prim_path}/geometry - The prim that contains the mesh and optionally the materials if configured. If instancing is enabled, this prim will be an instanceable reference to the prototype prim.

Caution

When converting STL files, Z-up convention is assumed, even though this is not the default for many CAD export programs. Asset orientation convention can either be modified directly in the CAD program’s export process or an offset can be added within the config in Isaac Lab.

Attributes:

cfg	The configuration instance for mesh to USD conversion.
usd_dir	The absolute path to the directory where the generated USD files are stored.
usd_file_name	The file name of the generated USD file.
usd_instanceable_meshes_path	The relative path to the USD file with meshes.
usd_path	The absolute path to the generated USD file.

Methods:

__init__(cfg)

Initializes the class.

cfg: MeshConverterCfg

The configuration instance for mesh to USD conversion.

__init__(cfg: MeshConverterCfg)

Initializes the class.

Parameters:

cfg – The configuration instance for mesh to USD conversion.

property usd_dir: str

The absolute path to the directory where the generated USD files are stored.

property usd_file_name: str

The file name of the generated USD file.

property usd_instanceable_meshes_path: str

The relative path to the USD file with meshes.

The path is with respect to the USD directory usd_dir. This is to ensure that the mesh references in the generated USD file are resolved relatively. Otherwise, it becomes difficult to move the USD asset to a different location.

property usd_path: str

The absolute path to the generated USD file.

class isaaclab.sim.converters.MeshConverterCfg

Bases: AssetConverterBaseCfg

The configuration class for MeshConverter.

Attributes:

mass_props	Mass properties to apply to the USD.
rigid_props	Rigid body properties to apply to the USD.
collision_props	Collision properties to apply to the USD.
asset_path	The absolute path to the asset file to convert into USD.
usd_dir	The output directory path to store the generated USD file.
usd_file_name	The name of the generated usd file.
force_usd_conversion	Force the conversion of the asset file to usd.
make_instanceable	Make the generated USD file instanceable.
mesh_collision_props	Mesh approximation properties to apply to all collision meshes in the USD.
translation	The translation of the mesh to the origin.
rotation	The rotation of the mesh in quaternion format (x, y, z, w).
scale	The scale of the mesh.

mass_props: MassPropertiesCfg

Mass properties to apply to the USD. Defaults to None.

Note

If None, then no mass properties will be added.

rigid_props: RigidBodyBaseCfg

Rigid body properties to apply to the USD. Defaults to None.

Note

If None, then no rigid body properties will be added.

collision_props: CollisionPropertiesCfg

Collision properties to apply to the USD. Defaults to None.

Note

If None, then no collision properties will be added.

asset_path: str

The absolute path to the asset file to convert into USD.

usd_dir: str | None

The output directory path to store the generated USD file. Defaults to None.

If None, it is resolved as /tmp/IsaacLab/usd_{date}_{time}_{random}, where the parameters in braces are runtime generated.

usd_file_name: str | None

The name of the generated usd file. Defaults to None.

If None, it is resolved from the asset file name. For example, if the asset file name is "my_asset.urdf", then the generated USD file name is "my_asset.usd".

If the providing file name does not end with “.usd” or “.usda”, then the extension “.usd” is appended to the file name.

force_usd_conversion: bool

Force the conversion of the asset file to usd. Defaults to False.

If True, then the USD file is always generated. It will overwrite the existing USD file if it exists.

make_instanceable: bool

Make the generated USD file instanceable. Defaults to True.

Note

Instancing helps reduce the memory footprint of the asset when multiple copies of the asset are used in the scene. For more information, please check the USD documentation on scene-graph instancing.

mesh_collision_props: MeshCollisionBaseCfg

Mesh approximation properties to apply to all collision meshes in the USD. .. note:: If None, then no mesh approximation properties will be added.

translation: tuple[float, float, float]

The translation of the mesh to the origin. Defaults to (0.0, 0.0, 0.0).

rotation: tuple[float, float, float, float]

The rotation of the mesh in quaternion format (x, y, z, w). Defaults to (0.0, 0.0, 0.0, 1.0).

scale: tuple[float, float, float]

The scale of the mesh. Defaults to (1.0, 1.0, 1.0).

URDF Converter

class isaaclab.sim.converters.UrdfConverter

Bases: AssetConverterBase

Converter for a URDF description file to a USD file.

This class wraps around the isaacsim.asset.importer.urdf extension to provide a lazy implementation for URDF to USD conversion. It stores the output USD file in an instanceable format since that is what is typically used in all learning related applications.

The heavy lifting (URDF parsing, fixed-joint merging, fix-base insertion, joint-drive configuration, density override, asset transformer profile) is delegated to Isaac Sim’s URDFImporter together with URDFImporterConfig. IsaacLab only translates its user-friendly UrdfConverterCfg into the flat importer config.

Caution

The current lazy conversion implementation does not automatically trigger USD generation if only the mesh files used by the URDF are modified. To force generation, either set AssetConverterBaseCfg.force_usd_conversion to True or delete the output directory.

Note

From Isaac Sim 4.5 onwards, the extension name changed from omni.importer.urdf to isaacsim.asset.importer.urdf.

Note

In the URDF importer 3.0, the conversion pipeline uses the urdf-usd-converter library and the isaacsim.asset.transformer.rules extension to produce structured USD output. Features such as convert_mimic_joints_to_normal_joints and replace_cylinders_with_capsules are no longer natively supported by the importer and will emit warnings if enabled.

Attributes:

cfg	The configuration instance for URDF to USD conversion.
usd_dir	The absolute path to the directory where the generated USD files are stored.
usd_file_name	The file name of the generated USD file.
usd_instanceable_meshes_path	The relative path to the USD file with meshes.
usd_path	The absolute path to the generated USD file.

Methods:

__init__(cfg)

Initializes the class.

cfg: UrdfConverterCfg

The configuration instance for URDF to USD conversion.

__init__(cfg: UrdfConverterCfg)

Initializes the class.

Parameters:

cfg – The configuration instance for URDF to USD conversion.

property usd_dir: str

The absolute path to the directory where the generated USD files are stored.

property usd_file_name: str

The file name of the generated USD file.

property usd_instanceable_meshes_path: str

The relative path to the USD file with meshes.

The path is with respect to the USD directory usd_dir. This is to ensure that the mesh references in the generated USD file are resolved relatively. Otherwise, it becomes difficult to move the USD asset to a different location.

property usd_path: str

The absolute path to the generated USD file.

class isaaclab.sim.converters.UrdfConverterCfg

Bases: AssetConverterBaseCfg

The configuration class for UrdfConverter.

Maps to URDFImporterConfig from the Isaac Sim URDF importer. IsaacLab exposes a user-friendly nested JointDriveCfg that is translated into the importer’s flat joint_drive_type / joint_target_type / override_joint_stiffness / override_joint_damping fields at conversion time.

Classes:

JointDriveCfg

Configuration for the joint drive.

Attributes:

fix_base	Create a fix joint to the root/base link.
root_link_name	The name of the root link.
link_density	Default density in kg/m^3 for links whose "inertial" properties are missing in the URDF.
merge_fixed_joints	Consolidate links that are connected by fixed joints.
asset_path	The absolute path to the asset file to convert into USD.
usd_dir	The output directory path to store the generated USD file.
usd_file_name	The name of the generated usd file.
force_usd_conversion	Force the conversion of the asset file to usd.
make_instanceable	Make the generated USD file instanceable.
convert_mimic_joints_to_normal_joints	Convert mimic joints to normal joints.
joint_drive	The joint drive settings.
collision_from_visuals	Whether to create collision geometry from visual geometry.
collision_type	The collision shape simplification.
self_collision	Activate self-collisions between links of the articulation.
replace_cylinders_with_capsules	Replace cylinder shapes with capsule shapes.
merge_mesh	Merge meshes where possible to optimize the model.
ros_package_paths	ROS package name/path mappings used to resolve package:// URLs in the URDF.
robot_type	Robot type applied by the USD robot schema.
run_asset_transformer	Run the asset transformation profile to convert the flattened USD into a layered USD asset.
run_multi_physics_conversion	Enable to generate compatible MuJoCo attributes from the URDF joint attributes alongside PhysX.
debug_mode	Enable debug mode in the underlying URDF importer.

class JointDriveCfg

Bases: object

Configuration for the joint drive.

Classes:

PDGainsCfg	Configuration for the PD gains of the drive.
NaturalFrequencyGainsCfg	Configuration for the natural frequency gains of the drive.

Attributes:

drive_type	The drive type used for the joint.
target_type	The drive target type used for the joint.
gains	The drive gains configuration.

class PDGainsCfg

Bases: object

Configuration for the PD gains of the drive.

Attributes:

stiffness	The stiffness of the joint drive in Nm/rad or N/rad.
damping	The damping of the joint drive in Nm/(rad/s) or N/(rad/s).

stiffness: dict[str, float] | float | None

The stiffness of the joint drive in Nm/rad or N/rad. Defaults to None.

If None, the stiffness values produced by the URDF importer are preserved. If target_type is set to "velocity", this value determines the drive strength in joint velocity space.

damping: dict[str, float] | float | None

The damping of the joint drive in Nm/(rad/s) or N/(rad/s). Defaults to None.

If None, the damping is set to the value parsed from the URDF file or 0.0 if no value is found in the URDF. If target_type is set to "velocity", this attribute is set to 0.0 and stiffness serves as the drive’s strength in joint velocity space.

class NaturalFrequencyGainsCfg

Bases: object

Configuration for the natural frequency gains of the drive.

Computes the joint drive stiffness and damping based on the desired natural frequency using the formula:

\(P = m \cdot f^2\), \(D = 2 \cdot r \cdot f \cdot m\)

where \(f\) is the natural frequency, \(r\) is the damping ratio, and \(m\) is the total equivalent inertia at the joint. The damping ratio is such that:

• \(r = 1.0\) is a critically damped system,

• \(r < 1.0\) is underdamped,

• \(r > 1.0\) is overdamped.

Deprecated since version This: gains mode is no longer supported by the URDF importer 3.0. The compute_natural_stiffness function has been removed. If used, a DeprecationWarning is emitted and joint drive gains are left at the values produced by the URDF importer. Use PDGainsCfg instead.

Attributes:

natural_frequency	The natural frequency of the joint drive.
damping_ratio	The damping ratio of the joint drive.

natural_frequency: dict[str, float] | float

The natural frequency of the joint drive.

If target_type is set to "velocity", this value determines the drive’s natural frequency in joint velocity space.

damping_ratio: dict[str, float] | float

The damping ratio of the joint drive. Defaults to 0.005.

If target_type is set to "velocity", this value is ignored and only natural_frequency is used.

drive_type: dict[str, Literal['acceleration', 'force']] | Literal['acceleration', 'force']

The drive type used for the joint. Defaults to "force".

• "acceleration": The joint drive normalizes the inertia before applying the joint effort so it’s invariant to inertia and mass changes (equivalent to ideal damped oscillator).

• "force": Applies effort through forces, so is subject to variations on the body inertia.

target_type: dict[str, Literal['none', 'position', 'velocity']] | Literal['none', 'position', 'velocity']

The drive target type used for the joint. Defaults to "position".

If the target type is set to "none", the joint stiffness and damping are set to 0.0.

gains: PDGainsCfg | NaturalFrequencyGainsCfg

The drive gains configuration.

fix_base: bool

Create a fix joint to the root/base link.

root_link_name: str | None

The name of the root link. Defaults to None.

If None, the root link will be set by PhysX.

Deprecated since version This: option is no longer supported by the URDF importer 3.0. A warning is logged if set.

link_density: float

Default density in kg/m^3 for links whose "inertial" properties are missing in the URDF. Defaults to 0.0.

A value of 0.0 leaves density unchanged.

merge_fixed_joints: bool

Consolidate links that are connected by fixed joints. Defaults to True.

When enabled, a URDF XML pre-processing step removes all fixed joints and merges each child link’s visual, collision, and inertial elements into the parent link before USD conversion. Downstream joints are re-parented with composed transforms. Chains of consecutive fixed joints are handled automatically. The pre-processing is performed by isaacsim.asset.importer.urdf.impl.urdf_utils.merge_fixed_joints().

asset_path: str

The absolute path to the asset file to convert into USD.

usd_dir: str | None

The output directory path to store the generated USD file. Defaults to None.

If None, it is resolved as /tmp/IsaacLab/usd_{date}_{time}_{random}, where the parameters in braces are runtime generated.

usd_file_name: str | None

The name of the generated usd file. Defaults to None.

If None, it is resolved from the asset file name. For example, if the asset file name is "my_asset.urdf", then the generated USD file name is "my_asset.usd".

If the providing file name does not end with “.usd” or “.usda”, then the extension “.usd” is appended to the file name.

force_usd_conversion: bool

Force the conversion of the asset file to usd. Defaults to False.

If True, then the USD file is always generated. It will overwrite the existing USD file if it exists.

make_instanceable: bool

Make the generated USD file instanceable. Defaults to True.

Note

Instancing helps reduce the memory footprint of the asset when multiple copies of the asset are used in the scene. For more information, please check the USD documentation on scene-graph instancing.

convert_mimic_joints_to_normal_joints: bool

Convert mimic joints to normal joints. Defaults to False.

Deprecated since version This: option is no longer supported by the URDF importer 3.0. A warning is logged if enabled.

joint_drive: JointDriveCfg | None

The joint drive settings. Defaults to JointDriveCfg.

The parameter can be set to None for URDFs without joints, in which case no joint drive overrides are sent to the importer.

collision_from_visuals: bool

Whether to create collision geometry from visual geometry. Defaults to False.

collision_type: Literal['Convex Hull', 'Convex Decomposition', 'Bounding Sphere', 'Bounding Cube']

The collision shape simplification. Defaults to "Convex Hull".

Supported values match the collision_type field of URDFImporterConfig:

• "Convex Hull": The collision shape is simplified to a convex hull.

• "Convex Decomposition": The collision shape is decomposed into smaller convex shapes for a closer fit.

• "Bounding Sphere": The collision shape is approximated by a bounding sphere.

• "Bounding Cube": The collision shape is approximated by a bounding cube.

self_collision: bool

Activate self-collisions between links of the articulation. Defaults to False.

replace_cylinders_with_capsules: bool

Replace cylinder shapes with capsule shapes. Defaults to False.

Deprecated since version This: option is no longer supported by the URDF importer 3.0. A warning is logged if enabled.

merge_mesh: bool

Merge meshes where possible to optimize the model. Defaults to False.

ros_package_paths: list[dict[str, str]]

ROS package name/path mappings used to resolve package:// URLs in the URDF.

Each entry is a dictionary with keys name and path. The list is forwarded directly to URDFImporterConfig.

robot_type: str

Robot type applied by the USD robot schema. Defaults to "Default".

Supported types are: Default, End Effector, Manipulator, Humanoid, Wheeled, Holonomic, Quadruped, Mobile Manipulators, Aerial. Forwarded to URDFImporterConfig.

run_asset_transformer: bool

Run the asset transformation profile to convert the flattened USD into a layered USD asset. Defaults to True.

After running this profile, the USD asset will be a layered USD asset with the following structure: - robot_name.usda (interface usd) - payloads/base.usda (base usd with links, meshes, and materials) - payloads/instances.usda (usd with visual and collision geometry) - payloads/geometry.usd (binary usd with meshes) - payloads/materials.usda (materials) - payloads/Physics/physics.usda (neutral physics format) - payloads/Physics/physX.usda (PhysX attributes) - payloads/Physics/mujoco.usda (MuJoCo attributes)

run_multi_physics_conversion: bool

Enable to generate compatible MuJoCo attributes from the URDF joint attributes alongside PhysX. Defaults to True.

debug_mode: bool

Enable debug mode in the underlying URDF importer. Defaults to False.

When enabled, the importer writes intermediate conversion artifacts next to the output USD for inspection instead of using a temporary scratch directory.

MJCF Converter

class isaaclab.sim.converters.MjcfConverter

Bases: AssetConverterBase

Converter for a MJCF description file to a USD file.

This class wraps around the isaacsim.asset.importer.mjcf extension to provide a lazy implementation for MJCF to USD conversion. All conversion logic (USD schema application, fix-base, density, actuator gains, self-collision, mesh merging, asset transformer profile) is performed by MJCFImporter — this class only translates MjcfConverterCfg into a flat MJCFImporterConfig.

Caution

The current lazy conversion implementation does not automatically trigger USD generation if only the mesh files used by the MJCF are modified. To force generation, either set AssetConverterBaseCfg.force_usd_conversion to True or delete the output directory.

Note

From Isaac Sim 5.0 onwards, the MJCF importer uses the mujoco-usd-converter library and the MJCFImporter / MJCFImporterConfig API. The old command-based API (MJCFCreateAsset / MJCFCreateImportConfig) is deprecated.

Note

The make_instanceable setting from the base class is not supported by the new MJCF importer and will be ignored.

Attributes:

cfg	The configuration instance for MJCF to USD conversion.
usd_dir	The absolute path to the directory where the generated USD files are stored.
usd_file_name	The file name of the generated USD file.
usd_instanceable_meshes_path	The relative path to the USD file with meshes.
usd_path	The absolute path to the generated USD file.

Methods:

__init__(cfg)

Initializes the class.

cfg: MjcfConverterCfg

The configuration instance for MJCF to USD conversion.

__init__(cfg: MjcfConverterCfg)

Initializes the class.

Parameters:

cfg – The configuration instance for MJCF to USD conversion.

property usd_dir: str

The absolute path to the directory where the generated USD files are stored.

property usd_file_name: str

The file name of the generated USD file.

property usd_instanceable_meshes_path: str

The relative path to the USD file with meshes.

The path is with respect to the USD directory usd_dir. This is to ensure that the mesh references in the generated USD file are resolved relatively. Otherwise, it becomes difficult to move the USD asset to a different location.

property usd_path: str

The absolute path to the generated USD file.

class isaaclab.sim.converters.MjcfConverterCfg

Bases: AssetConverterBaseCfg

The configuration class for MjcfConverter.

Maps to MJCFImporterConfig from the Isaac Sim MJCF importer. All post-import USD edits (fix-base, density override, actuator gain overrides, self-collision, mesh merging, asset transformer profile) are performed by the Isaac Sim importer — this config just forwards the user’s choices.

Note

From Isaac Sim 5.0 onwards, the MJCF importer was rewritten to use the mujoco-usd-converter library. The AssetConverterBaseCfg.make_instanceable setting from the base class is not supported by the new MJCF importer and is ignored.

Attributes:

merge_mesh	Merge meshes where possible to optimize the model.
collision_from_visuals	Generate collision geometry from visual geometries.
collision_type	Type of collision geometry to use.
self_collision	Activate self-collisions between links of the articulation.
import_physics_scene	Import the physics scene (time step per second, gravity, etc.) from the MJCF file.
fix_base	Add a fixed joint from the world to the root rigid-body link.
link_density	Default density in kg/m^3 for links whose "inertial" properties are missing.
asset_path	The absolute path to the asset file to convert into USD.
usd_dir	The output directory path to store the generated USD file.
usd_file_name	The name of the generated usd file.
force_usd_conversion	Force the conversion of the asset file to usd.
make_instanceable	Make the generated USD file instanceable.
robot_type	Robot type applied by the USD robot schema.
override_gain_type	MuJoCo actuator gain type override (e.g. "fixed").
override_bias_type	MuJoCo actuator bias type override (e.g. "affine").
override_gain_prm	MuJoCo actuator gain parameter array override.
override_bias_prm	MuJoCo actuator bias parameter array override.
run_asset_transformer	Run the asset transformation profile to convert the flattened USD into a layered USD asset.
run_multi_physics_conversion	Enable to convert compatible MuJoCo attributes to PhysX attributes, such as actuator gains.
debug_mode	Enable debug mode in the underlying MJCF importer.

merge_mesh: bool

Merge meshes where possible to optimize the model. Defaults to False.

collision_from_visuals: bool

Generate collision geometry from visual geometries. Defaults to False.

collision_type: Literal['Convex Hull', 'Convex Decomposition', 'Bounding Sphere', 'Bounding Cube']

Type of collision geometry to use. Defaults to "Convex Hull".

Supported values match the collision_type field of MJCFImporterConfig.

self_collision: bool

Activate self-collisions between links of the articulation. Defaults to False.

import_physics_scene: bool

Import the physics scene (time step per second, gravity, etc.) from the MJCF file. Defaults to False.

fix_base: bool

Add a fixed joint from the world to the root rigid-body link. Defaults to False.

When enabled, MJCFImporter inserts a FixedJoint between the world and the articulation root and relocates ArticulationRootAPI onto the appropriate ancestor prim so PhysX treats the articulation as fixed-base.

link_density: float

Default density in kg/m^3 for links whose "inertial" properties are missing. Defaults to 0.0.

A value of 0.0 leaves density unchanged.

asset_path: str

The absolute path to the asset file to convert into USD.

usd_dir: str | None

The output directory path to store the generated USD file. Defaults to None.

If None, it is resolved as /tmp/IsaacLab/usd_{date}_{time}_{random}, where the parameters in braces are runtime generated.

usd_file_name: str | None

The name of the generated usd file. Defaults to None.

If None, it is resolved from the asset file name. For example, if the asset file name is "my_asset.urdf", then the generated USD file name is "my_asset.usd".

If the providing file name does not end with “.usd” or “.usda”, then the extension “.usd” is appended to the file name.

force_usd_conversion: bool

Force the conversion of the asset file to usd. Defaults to False.

If True, then the USD file is always generated. It will overwrite the existing USD file if it exists.

make_instanceable: bool

Make the generated USD file instanceable. Defaults to True.

Note

Instancing helps reduce the memory footprint of the asset when multiple copies of the asset are used in the scene. For more information, please check the USD documentation on scene-graph instancing.

robot_type: str

Robot type applied by the USD robot schema. Defaults to "Default".

Supported types are: Default, End Effector, Manipulator, Humanoid, Wheeled, Holonomic, Quadruped, Mobile Manipulators, Aerial. Forwarded to MJCFImporterConfig.

override_gain_type: str | None

MuJoCo actuator gain type override (e.g. "fixed"). Defaults to None.

None leaves the value parsed from the MJCF file unchanged. See isaacsim.asset.importer.utils.impl.asset_utils.apply_mjc_actuator_gains() for the supported encodings.

override_bias_type: str | None

MuJoCo actuator bias type override (e.g. "affine"). Defaults to None.

None leaves the value parsed from the MJCF file unchanged.

override_gain_prm: list[float] | None

MuJoCo actuator gain parameter array override. Defaults to None.

Mujoco models actuators using an affine transformation, which is a linear combination of the gain parameters, control, and bias.

The affine transformation is defined as: tau = gain @ control + bias

None leaves the value parsed from the MJCF file unchanged. Example for position control: [kp, 0, 0, 0, 0, 0, 0, 0, 0, 0].

override_bias_prm: list[float] | None

MuJoCo actuator bias parameter array override. Defaults to None.

None leaves the value parsed from the MJCF file unchanged. Example for position control: [0, -kp, -kd, 0, 0, 0, 0, 0, 0, 0].

run_asset_transformer: bool

Run the asset transformation profile to convert the flattened USD into a layered USD asset. Defaults to True.

After running this profile, the USD asset will be a layered USD asset with the following structure: - robot_name.usda (interface usd) - payloads/base.usda (base usd with links, meshes, and materials) - payloads/instances.usda (usd with visual and collision geometry) - payloads/geometry.usd (binary usd with meshes) - payloads/materials.usda (materials) - payloads/Physics/physics.usda (neutral physics format) - payloads/Physics/physX.usda (PhysX attributes) - payloads/Physics/mujoco.usda (MuJoCo attributes)

run_multi_physics_conversion: bool

Enable to convert compatible MuJoCo attributes to PhysX attributes, such as actuator gains. Defaults to True.

debug_mode: bool

Enable debug mode in the underlying MJCF importer. Defaults to False.

When enabled, the importer writes intermediate conversion artifacts next to the output USD for inspection instead of using a temporary scratch directory.