How to add URDF to World?

Omniverse Isaac Sim
1

Hi,

I noticed when adding an URDF using the GUI, it by default, adds it under the default /World prim.

However, when I load the URDF using the Python, i.e.,

status, stage_path = omni.kit.commands.execute(
    "URDFParseAndImportFile",
    urdf_path=urdf_path,
    import_config=import_config,
)

It loads at the same level as the /World prim. My question is how can the URDF loaded object be included into the /World prim?

Thanks in advance! For your reference, the entire code I am using is

from isaacsim import SimulationApp

kit = SimulationApp({"renderer": "RayTracedLighting", "headless": False})

import omni.kit.commands
from omni.importer.urdf import _urdf
from omni.isaac.core import World
from omni.isaac.core.articulations import Articulation
from pxr import Gf, PhysxSchema, Sdf, UsdLux, UsdPhysics

my_world = World(stage_units_in_meters=1.0)
my_world.scene.add_default_ground_plane()

status, import_config = omni.kit.commands.execute("URDFCreateImportConfig")
import_config.fix_base = False
import_config.default_drive_type = _urdf.UrdfJointTargetType.JOINT_DRIVE_VELOCITY

turtlebot3_urdf_path = "/home/bolun/Documents/IsaacSim-ros_workspaces/humble_ws/src/turtlebot3/turtlebot3_description/urdf/turtlebot3_burger.urdf"

# Import URDF, stage_path contains the path the path to the usd prim in the stage.
status, stage_path = omni.kit.commands.execute(
    "URDFParseAndImportFile",
    urdf_path=turtlebot3_urdf_path,
    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)

# Set solver settings
PhysxSchema.PhysxSceneAPI.Apply(stage.GetPrimAtPath("/physicsScene"))
physxSceneAPI = PhysxSchema.PhysxSceneAPI.Get(stage, "/physicsScene")
physxSceneAPI.CreateEnableCCDAttr(True)
physxSceneAPI.CreateEnableStabilizationAttr(True)
physxSceneAPI.CreateEnableGPUDynamicsAttr(False)
physxSceneAPI.CreateBroadphaseTypeAttr("MBP")
physxSceneAPI.CreateSolverTypeAttr("TGS")

# Add ground plane
omni.kit.commands.execute(
    "AddGroundPlaneCommand",
    stage=stage,
    planePath="/groundPlane",
    axis="Z",
    size=1500.0,
    position=Gf.Vec3f(0, 0, -50),
    color=Gf.Vec3f(0.5),
)

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

my_world.reset()
art = Articulation(prim_path=stage_path)
art.initialize()

if not art.handles_initialized:
    print(f"{stage_path} is not an articulation")
else:
    print(f"Got articulation {stage_path}")

# perform simulation
while kit.is_running():
    my_world.step(render=True)

# Shutdown and exit
kit.close()
2

Did you ever get this solved?

3

I ended up loading it and then moving it:

        status = omni.kit.commands.execute('MovePrimCommand',
                                           path_from=stage_path,
                                           path_to=prim_path,
                                           )

prim_path was where I wanted it to be.

4

Import a URDF or any kind of robot is just the beginning. I thing just use the URDF importer and get a usd file is enough. Do not let python script be a burden. About the prim tree, it is easier to modify it using Isaac Sim UI.
If you really want to use python, learn how _setup_scene() or setup_scene() load the assets in simulation environments.