Questions regarding USD scenes and Isaac Sim

Omniverse Isaac Sim
1

Hi all,

I am completely new to Isaac, Omniverse, and in general 3D things, so my questions may have been answered before but I could not find the right answers. For context, I’m a gazebo user and I am curious as to how Isaac performs in large scene with many objects, and fast moving robots.

To do that in gazebo it’s fairly straight forward, you define a big text file in which you say where is what and its scale. My issue is how do I do that in Isaac. I understand Isaac is using USD files to define what the scene will look like, and that all the assets should be defined as USD files. But how do I make that scene ?

I mean in my case the scene is procedurally generated by some python code. Hence, I’d rather avoid building the scene manually and I was looking for ways to make it using code. So far I have found the code snippets provided in the doc but there is something that I can’t find. From the doc I know how to add a cube, a sphere, how to apply randomization, but I don’t know how to import an asset. And I guess I would if I could find the list of commands. By that I mean that all the time the tutorial call something like:

omni.kit.commands.execute(“CreateMeshPrimCommand”, prim_type=“Cube”)

How do I do that for assets ? Is there a list of commands somewhere ? I could not find it.

A separate question I have is does Isaac sim supports height-maps / digital elevation models ?

Thanks in advance,

Best,

Antoine

2

I’ll answer part of my question:
Here is how you can add an asset using python:

def create_object(prefix, stage, path, location=Gf.Vec3d(0, 0, 0), rotation=Gf.Quaternion(1, Gf.Vec3d(0,0,0)), group=[]):
    """
    Creates a 3D object from a USD file and adds it into the scene with a given rotation and location
    Inputs:
        prefix: The name of the object in the world (does not have to be unique).
        stage: The name of the world the objects belong to.
        path: The path of to the USD file on the docker/drive.
        location: The position of the object relatively to the stage.
        rotation: The rotation of the object relatively to the stage.
        group: The group of primitives this object belongs to.
    Outputs:
        group: The group of primitives this object belongs to.
    """
    prim_path = omni.usd.get_stage_next_free_path(stage, prefix, False)
    group.append(prim_path)
    tile_prim = stage.DefinePrim(prim_path, "Xform")
    tile_prim.GetReferences().AddReference(path)
    xform = UsdGeom.Xformable(tile_prim)
    xform_op = xform.AddXformOp(UsdGeom.XformOp.TypeTransform, UsdGeom.XformOp.PrecisionDouble, "")
    mat = Gf.Matrix4d().SetTranslate(location)
    mat.SetRotateOnly(Gf.Rotation(rotation))
    xform_op.Set(mat)
    return group

I could not find the list of commands but I assume most of them are listed in here Index — isaac_sim 2022.1.1-release.1 documentation

3

Hi Antoine,

I am glad you found your own answer, and yes that is the link to Isaac Sim API doc.
Please let us know if you still have questions.

Kindly,
Liila

4

Thanks for the answer, do you know if isaac sim support heightmap or should I convert my heightmap into stl files and then into usd files ?

5

Hi Antoine,

Unfortunately we currently do not support heightmap., you can probably convert it yourself.

Kindly,
Liila

6

Thanks, will do.

7

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