[Question] How to spawn arbitary number of objects in one environment?

[YZhang001]

Question

I'm trying to spawn multiple assets in one environment. I was following the tutorial and looked at some example codes of Orbit using the following structure:

@configclass
class TableTopSceneCfg(InteractiveSceneCfg):

    # ground plane
    ground = AssetBaseCfg(
        prim_path="/World/defaultGroundPlane",
        spawn=sim_utils.GroundPlaneCfg(),
        init_state=AssetBaseCfg.InitialStateCfg(pos=(0.0, 0.0, -1.05)),
    )

    # lights
    dome_light = AssetBaseCfg(
        prim_path="/World/Light", spawn=sim_utils.DomeLightCfg(intensity=3000.0, color=(0.75, 0.75, 0.75))
    )

    table = AssetBaseCfg(
        prim_path="{ENV_REGEX_NS}/Table",
        spawn=sim_utils.UsdFileCfg(
            usd_path=f"{ISAAC_NUCLEUS_DIR}/Props/Mounts/thor_table.usd", scale=(1.5, 1.5, 1.0)
            # usd_path=f"{ISAAC_NUCLEUS_DIR}/Props/Mounts/Stand/stand_instanceable.usd", scale=(2.0, 2.0, 2.0)
        ),
    )
......

What I need would be, for example, to spawn multiple spheres in one environment with different positions, rotations, and so on. With the configclass above I added several spheres into the environment with:

    sphere_i = AssetBaseCfg(
            prim_path="{ENV_REGEX_NS}/Pose_Sphere_" + str(i),
            spawn=sim_utils.UsdFileCfg(
                usd_path=f"{ISAAC_NUCLEUS_DIR}/Props/Shapes/sphere.usd", 
                scale=(1.0 * scale_obstacle_spwan[i][0], 1.0 * scale_obstacle_spwan[i][1], 1.0 * scale_obstacle_spwan[i][2]), 
            ),
            init_state=AssetBaseCfg.InitialStateCfg(pos=(pos_obstacle_spwan[i][0], pos_obstacle_spwan[i][1], pos_obstacle_spwan[i][2]), 
                                                    rot=(quat_obstacle_spawn[i][3], quat_obstacle_spawn[i][0], quat_obstacle_spawn[i][1], quat_obstacle_spawn[i][2])
        )
    )

where I repeated the snippet above and manually specified the index i. But spawning assets this way is highly inefficient and easy to make mistakes. So I tried to initialize a list before setting up the class and assign assets for each element in the list:

spawn_spheres = [[]] * num_spheres

@configclass
class TableTopSceneCfg(InteractiveSceneCfg):
...

    for spawn_spheres_id in range(num_spheres):
        spawn_spheres[spawn_spheres_id] = AssetBaseCfg(
                prim_path="{ENV_REGEX_NS}/Pose_Sphere_" + str(spawn_spheres_id),
                spawn=sim_utils.UsdFileCfg(
                    usd_path=f"{ISAAC_NUCLEUS_DIR}/Props/Shapes/sphere.usd", 
                    scale=(1.0 * scale_obstacle_spwan[spawn_spheres_id][0], 1.0 * scale_obstacle_spwan[spawn_spheres_id][1], 1.0 * scale_obstacle_spwan[spawn_spheres_id][2]), 
                ),
                init_state=AssetBaseCfg.InitialStateCfg(pos=(pos_obstacle_spwan[spawn_spheres_id][0], pos_obstacle_spwan[spawn_spheres_id][1], pos_obstacle_spwan[spawn_spheres_id][2]), 
                                                        rot=(quat_obstacle_spawn[spawn_spheres_id][3], quat_obstacle_spawn[spawn_spheres_id][0], quat_obstacle_spawn[spawn_spheres_id][1], quat_obstacle_spawn[spawn_spheres_id][2])
            )
        )
...

But this will cause an error:

File "...", line 1717, in
main()
File "...", line 1702, in main
scene = InteractiveScene(scene_cfg)
File ".../orbit/source/extensions/omni.isaac.orbit/omni/isaac/orbit/scene/interactive_scene.py", line 101, in init
self._add_entities_from_cfg()
File ".../orbit/source/extensions/omni.isaac.orbit/omni/isaac/orbit/scene/interactive_scene.py", line 333, in _add_entities_from_cfg
asset_cfg.prim_path = asset_cfg.prim_path.format(ENV_REGEX_NS=self.env_regex_ns)
AttributeError: 'int' object has no attribute 'prim_path'

It is the same even if I do:

for spawn_spheres_id in range(num_spheres):
    spawn_spheres.append(AssetBaseCfg(
                    prim_path="{ENV_REGEX_NS}/Pose_Sphere_" + str(spawn_spheres_id),
                    spawn=sim_utils.UsdFileCfg(
                        usd_path=f"{ISAAC_NUCLEUS_DIR}/Props/Shapes/sphere.usd", 
                        scale=(1.0 * scale_obstacle_spwan[spawn_spheres_id][0], 1.0 * scale_obstacle_spwan[spawn_spheres_id][1], 1.0 * scale_obstacle_spwan[spawn_spheres_id][2]), 
                    ),
                    init_state=AssetBaseCfg.InitialStateCfg(pos=(pos_obstacle_spwan[spawn_spheres_id][0], pos_obstacle_spwan[spawn_spheres_id][1], pos_obstacle_spwan[spawn_spheres_id][2]), 
                                                            rot=(quat_obstacle_spawn[spawn_spheres_id][3], quat_obstacle_spawn[spawn_spheres_id][0], quat_obstacle_spawn[spawn_spheres_id][1], quat_obstacle_spawn[spawn_spheres_id][2])
                )
            ))

before passing the list into the configclass.

I'm writing to ask if there is a proper way to automatically spawn multiple assets in one environment. Thank you.

[meenalparakh]

I believe the cfgs are supposed to be members of the TableTop scene cfg class. For me, something like the following worked

class TableTopSceneCfg(InteractiveSceneCfg):
    def __init__(*args, **kwargs):
        super().__init__(*args, **kwargs)
        self.dome_light = AssetBaseCfg(...)
        self.ground = AssetBaseCfg(...)

      # collect all configs
       sphere_cfgs = {}
       for i in range(N):
           sphere_cfgs[f"sphere_{i}"] = AssetBaseCfg(...)

       # set the cfgs as members of the class
       for k, v in sphere_cfgs.items():
           self.__setattr__(k, v)