[isaacsim.asset.importer.urdf] Urdf Importer Extension

Version: 2.4.13

URDF Importer

Enable Extension

The extension can be enabled (if not already) in one of the following ways:

Command-line interface

Define the next entry as an application argument from a terminal.

APP_SCRIPT.(sh|bat) --enable isaacsim.asset.importer.urdf

Experience/extension configuration

Define the next entry under [dependencies] in an experience (.kit) file or an extension configuration (extension.toml) file.

[dependencies]
"isaacsim.asset.importer.urdf" = {}

Extension Manager UI

Open the Window > Extensions menu in a running application instance and search for isaacsim.asset.importer.urdf. Then, toggle the enable control button if it is not already active.

URDF Import Extension [isaacsim.asset.importer.urdf]

URDF Import Commands

The following commands can be used to simplify the import process. Below is a sample demonstrating how to import the Carter URDF included with this extension

import omni.kit.commands
from pxr import UsdLux, Sdf, Gf, UsdPhysics, PhysicsSchemaTools

# setting up import configuration:
status, import_config = omni.kit.commands.execute("URDFCreateImportConfig")
import_config.merge_fixed_joints = False
import_config.convex_decomp = False
import_config.import_inertia_tensor = True
import_config.fix_base = False
import_config.collision_from_visuals = False

# Get path to extension data:
ext_manager = omni.kit.app.get_app().get_extension_manager()
ext_id = ext_manager.get_enabled_extension_id("isaacsim.asset.importer.urdf")
extension_path = ext_manager.get_extension_path(ext_id)
# import URDF
omni.kit.commands.execute(
    "URDFParseAndImportFile",
    urdf_path=extension_path + "/data/urdf/robots/carter/urdf/carter.urdf",
    import_config=import_config,
)
# get stage handle
stage = omni.usd.get_context().get_stage()

# enable physics
scene = UsdPhysics.Scene.Define(stage, Sdf.Path("/physicsScene"))
# set gravity
scene.CreateGravityDirectionAttr().Set(Gf.Vec3f(0.0, 0.0, -1.0))
scene.CreateGravityMagnitudeAttr().Set(9.81)

# add ground plane
PhysicsSchemaTools.addGroundPlane(stage, "/World/groundPlane", "Z", 1500, Gf.Vec3f(0, 0, -50), Gf.Vec3f(0.5))

# add lighting
distantLight = UsdLux.DistantLight.Define(stage, Sdf.Path("/DistantLight"))
distantLight.CreateIntensityAttr(500)

class URDFCreateImportConfig(*args: Any, **kwargs: Any)

Returns an ImportConfig object that can be used while parsing and importing. Should be used with URDFParseFile and URDFParseAndImportFile commands

Returns:

Parsed URDF stored in an internal structure.

Return type:

isaacsim.asset.importer.urdf._urdf.ImportConfig

class URDFImportRobot(*args: Any, **kwargs: Any)

This command parses and imports a given urdf and returns a UrdfRobot object

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (UrdfRobot) – The parsed URDF Robot

• arg2 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import Configuration

• arg3 (str) – destination path for robot usd. Default is “” which will load the robot in-memory on the open stage.

• arg4 (bool) – if True, return the articulation Root prim path instead of the object’s base path.

Returns:

Path to the robot on the USD stage.

Return type:

str

class URDFParseAndImportFile(*args: Any, **kwargs: Any)

This command parses and imports a given urdf and returns a UrdfRobot object

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import Configuration

• arg2 (str) – destination path for robot usd. Default is “” which will load the robot in-memory on the open stage.

• arg3 (bool) – if True, return the articulation Root prim path instead of the object’s base path.

Returns:

Path to the robot on the USD stage.

Return type:

str

class URDFParseFile(*args: Any, **kwargs: Any)

This command parses a given urdf and returns a UrdfRobot object

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import Configuration

Returns:

Parsed URDF stored in an internal structure.

Return type:

isaacsim.asset.importer.urdf._urdf.UrdfRobot

class URDFParseText(*args: Any, **kwargs: Any)

This command parses a given urdf and returns a UrdfRobot object

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import Configuration

Returns:

Parsed URDF stored in an internal structure.

Return type:

isaacsim.asset.importer.urdf._urdf.UrdfRobot

This extension provides an interface to the URDF importer.

Example

Setup the configuration parameters before importing. Files must be parsed before imported.

from isaacsim.asset.importer.urdf import _urdf
urdf_interface = _urdf.acquire_urdf_interface()

# setup config params
import_config = _urdf.ImportConfig()
import_config.set_merge_fixed_joints(False)
import_config.set_fix_base(True)

# parse and import file
imported_robot = urdf_interface.parse_urdf(robot_path, filename, import_config)
urdf_interface.import_robot(robot_path, filename, imported_robot, import_config, "")

Refer to the sample documentation for more examples and usage

class Urdf

compute_natural_stiffness(

self: isaacsim.asset.importer.urdf._urdf.Urdf,

arg0: isaacsim.asset.importer.urdf._urdf.UrdfRobot,

arg1: str,

arg2: float,

) → float

Compute the natural stiffness of a joint.

Parameters:

• arg0 (isaacsim.asset.importer.urdf._urdf.UrdfRobot) – The parsed URDF, the output from parse_urdf

• arg1 (str) – The name of the joint

• arg2 (float) – The natural frequency of the joint

Returns:

The natural stiffness of the joint

Return type:

float

get_kinematic_chain(

self: isaacsim.asset.importer.urdf._urdf.Urdf,

arg0: isaacsim.asset.importer.urdf._urdf.UrdfRobot,

) → dict

Get the kinematic chain of the robot. Mostly used for graphic display of the kinematic tree.

Parameters:

arg0 (isaacsim.asset.importer.urdf._urdf.UrdfRobot) – The parsed URDF, the output from parse_urdf

Returns:

A dictionary with information regarding the parent-child relationship between all the links and joints

Return type:

dict

import_robot(

self: isaacsim.asset.importer.urdf._urdf.Urdf,

assetRoot: str,

assetName: str,

robot: isaacsim.asset.importer.urdf._urdf.UrdfRobot,

importConfig: isaacsim.asset.importer.urdf._urdf.ImportConfig,

stage: str = '',

getArticulationRoot: bool = False,

) → str

Importing the robot, from the already parsed URDF file.

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (str) – The name of the urdf file

• arg2 (isaacsim.asset.importer.urdf._urdf.UrdfRobot) – The parsed URDF file, the output from parse_urdf

• arg3 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import configuration parameters

• arg4 (str) – optional: path to stage to use for importing. leaving it empty will import on open stage. If the open stage is a new stage, textures will not load.

Returns:

Path to the robot on the USD stage.

Return type:

str

parse_string_urdf(

self: isaacsim.asset.importer.urdf._urdf.Urdf,

arg0: str,

arg1: isaacsim.asset.importer.urdf._urdf.ImportConfig,

) → isaacsim.asset.importer.urdf._urdf.UrdfRobot

Parse URDF file into the internal data structure, which is displayed in the importer window for inspection.

Parameters:

• arg0 (str) – The urdf in text format

• arg2 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import configuration parameters

Returns:

Parsed URDF stored in an internal structure.

Return type:

isaacsim.asset.importer.urdf._urdf.UrdfRobot

parse_urdf(

self: isaacsim.asset.importer.urdf._urdf.Urdf,

arg0: str,

arg1: str,

arg2: isaacsim.asset.importer.urdf._urdf.ImportConfig,

) → isaacsim.asset.importer.urdf._urdf.UrdfRobot

Parse URDF file into the internal data structure, which is displayed in the importer window for inspection.

Parameters:

• arg0 (str) – The absolute path to where the urdf file is

• arg1 (str) – The name of the urdf file

• arg2 (isaacsim.asset.importer.urdf._urdf.ImportConfig) – Import configuration parameters

Returns:

Parsed URDF stored in an internal structure.

Return type:

isaacsim.asset.importer.urdf._urdf.UrdfRobot

class ImportConfig

set_collision_from_visuals(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_convex_decomp(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_create_physics_scene(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_default_drive_strength(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: float,

) → None

set_default_drive_type(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: int,

) → None

set_default_position_drive_damping(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: float,

) → None

set_density(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: float,

) → None

set_distance_scale(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: float,

) → None

set_fix_base(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_import_inertia_tensor(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_make_default_prim(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_merge_fixed_joints(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_override_joint_dynamics(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_parse_mimic(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_replace_cylinders_with_capsules(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_self_collision(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: bool,

) → None

set_subdivision_scheme(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: int,

) → None

set_up_vector(

self: isaacsim.asset.importer.urdf._urdf.ImportConfig,

arg0: float,

arg1: float,

arg2: float,

) → None

property collision_from_visuals

Generate convex collision from the visual meshes.

property convex_decomp

Decompose a convex mesh into smaller pieces for a closer fit

property create_physics_scene

add a physics scene to the stage on import if none exists

property default_drive_strength

default drive stiffness used for joints if drive type is position or velocity and none is authored

property default_drive_type

default drive type used for joints

property default_position_drive_damping

default drive damping used if drive type is set to position and no damping is authored

property density

default density used for links, use 0 to autocompute

property distance_scale

Set the unit scaling factor, 1.0 means meters, 100.0 means cm

property fix_base

Create fix joint for base link

property import_inertia_tensor

Import inertia tensor from urdf, if not specified in urdf it will import as identity

property make_default_prim

set imported robot as default prim

property merge_fixed_joints

Consolidating links that are connected by fixed joints

property override_joint_dynamics

Use default values for all joints

property parse_mimic

Parse Mimic Joint flag using PhysX Tendons

property replace_cylinders_with_capsules

Replace all cylinder bodies in the URDF with capsules.

property self_collision

Self collisions between links in the articulation

property subdivision_scheme

Subdivision scheme to be used for mesh normals

property up_vector

Up vector used for import

Settings

Other Settings

The extension changes some settings of the application or other extensions, which are listed in the table below.

Application/extension setting	Description	Value
exts."omni.kit.window.filepicker".detail_width_init	Set the initial width of the file picker to 390	390
exts."omni.kit.window.filepicker".detail_width_min	Set the minimum width of the file picker to 390	390
exts."omni.kit.window.filepicker".detail_width_max	Set the maximum width of the file picker to 600	600