Spawning Multiple Assets#
Typical, spawning configurations (introduced in the Spawning prims into the scene tutorial) copy the same asset (or USD primitive) across the different resolved prim paths from the expressions. For instance, if the user specifies to spawn the asset at “/World/Table_.*/Object”, the same asset is created at the paths “/World/Table_0/Object”, “/World/Table_1/Object” and so on.
However, at times, it might be desirable to spawn different assets under the prim paths to ensure a diversity in the simulation. This guide describes how to create different assets under each prim path using the spawning functionality.
The sample script multi_asset.py is used as a reference, located in the
IsaacLab/source/standalone/demos directory.
Code for multi_asset.py
1# Copyright (c) 2022-2024, The Isaac Lab Project Developers.
2# All rights reserved.
3#
4# SPDX-License-Identifier: BSD-3-Clause
5
6"""This script demonstrates how to spawn multiple objects in multiple environments.
7
8.. code-block:: bash
9
10 # Usage
11 ./isaaclab.sh -p source/standalone/demos/multi_asset.py --num_envs 2048
12
13"""
14
15from __future__ import annotations
16
17"""Launch Isaac Sim Simulator first."""
18
19
20import argparse
21
22from omni.isaac.lab.app import AppLauncher
23
24# add argparse arguments
25parser = argparse.ArgumentParser(description="Demo on spawning different objects in multiple environments.")
26parser.add_argument("--num_envs", type=int, default=1024, help="Number of environments to spawn.")
27# append AppLauncher cli args
28AppLauncher.add_app_launcher_args(parser)
29# parse the arguments
30args_cli = parser.parse_args()
31
32# launch omniverse app
33app_launcher = AppLauncher(args_cli)
34simulation_app = app_launcher.app
35
36"""Rest everything follows."""
37
38import random
39
40import omni.usd
41from pxr import Gf, Sdf
42
43import omni.isaac.lab.sim as sim_utils
44from omni.isaac.lab.assets import ArticulationCfg, AssetBaseCfg, RigidObjectCfg
45from omni.isaac.lab.scene import InteractiveScene, InteractiveSceneCfg
46from omni.isaac.lab.sim import SimulationContext
47from omni.isaac.lab.utils import Timer, configclass
48from omni.isaac.lab.utils.assets import ISAACLAB_NUCLEUS_DIR
49
50##
51# Pre-defined Configuration
52##
53
54from omni.isaac.lab_assets.anymal import ANYDRIVE_3_LSTM_ACTUATOR_CFG # isort: skip
55
56
57##
58# Randomization events.
59##
60
61
62def randomize_shape_color(prim_path_expr: str):
63 """Randomize the color of the geometry."""
64 # acquire stage
65 stage = omni.usd.get_context().get_stage()
66 # resolve prim paths for spawning and cloning
67 prim_paths = sim_utils.find_matching_prim_paths(prim_path_expr)
68 # manually clone prims if the source prim path is a regex expression
69 with Sdf.ChangeBlock():
70 for prim_path in prim_paths:
71 # spawn single instance
72 prim_spec = Sdf.CreatePrimInLayer(stage.GetRootLayer(), prim_path)
73
74 # DO YOUR OWN OTHER KIND OF RANDOMIZATION HERE!
75 # Note: Just need to acquire the right attribute about the property you want to set
76 # Here is an example on setting color randomly
77 color_spec = prim_spec.GetAttributeAtPath(prim_path + "/geometry/material/Shader.inputs:diffuseColor")
78 color_spec.default = Gf.Vec3f(random.random(), random.random(), random.random())
79
80
81##
82# Scene Configuration
83##
84
85
86@configclass
87class MultiObjectSceneCfg(InteractiveSceneCfg):
88 """Configuration for a multi-object scene."""
89
90 # ground plane
91 ground = AssetBaseCfg(prim_path="/World/defaultGroundPlane", spawn=sim_utils.GroundPlaneCfg())
92
93 # lights
94 dome_light = AssetBaseCfg(
95 prim_path="/World/Light", spawn=sim_utils.DomeLightCfg(intensity=3000.0, color=(0.75, 0.75, 0.75))
96 )
97
98 # rigid object
99 object: RigidObjectCfg = RigidObjectCfg(
100 prim_path="/World/envs/env_.*/Object",
101 spawn=sim_utils.MultiAssetSpawnerCfg(
102 assets_cfg=[
103 sim_utils.ConeCfg(
104 radius=0.3,
105 height=0.6,
106 visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.0, 1.0, 0.0), metallic=0.2),
107 ),
108 sim_utils.CuboidCfg(
109 size=(0.3, 0.3, 0.3),
110 visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(1.0, 0.0, 0.0), metallic=0.2),
111 ),
112 sim_utils.SphereCfg(
113 radius=0.3,
114 visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.0, 0.0, 1.0), metallic=0.2),
115 ),
116 ],
117 random_choice=True,
118 rigid_props=sim_utils.RigidBodyPropertiesCfg(
119 solver_position_iteration_count=4, solver_velocity_iteration_count=0
120 ),
121 mass_props=sim_utils.MassPropertiesCfg(mass=1.0),
122 collision_props=sim_utils.CollisionPropertiesCfg(),
123 ),
124 init_state=RigidObjectCfg.InitialStateCfg(pos=(0.0, 0.0, 2.0)),
125 )
126
127 # articulation
128 robot: ArticulationCfg = ArticulationCfg(
129 prim_path="/World/envs/env_.*/Robot",
130 spawn=sim_utils.MultiUsdFileCfg(
131 usd_path=[
132 f"{ISAACLAB_NUCLEUS_DIR}/Robots/ANYbotics/ANYmal-C/anymal_c.usd",
133 f"{ISAACLAB_NUCLEUS_DIR}/Robots/ANYbotics/ANYmal-D/anymal_d.usd",
134 ],
135 random_choice=True,
136 rigid_props=sim_utils.RigidBodyPropertiesCfg(
137 disable_gravity=False,
138 retain_accelerations=False,
139 linear_damping=0.0,
140 angular_damping=0.0,
141 max_linear_velocity=1000.0,
142 max_angular_velocity=1000.0,
143 max_depenetration_velocity=1.0,
144 ),
145 articulation_props=sim_utils.ArticulationRootPropertiesCfg(
146 enabled_self_collisions=True, solver_position_iteration_count=4, solver_velocity_iteration_count=0
147 ),
148 activate_contact_sensors=True,
149 ),
150 init_state=ArticulationCfg.InitialStateCfg(
151 pos=(0.0, 0.0, 0.6),
152 joint_pos={
153 ".*HAA": 0.0, # all HAA
154 ".*F_HFE": 0.4, # both front HFE
155 ".*H_HFE": -0.4, # both hind HFE
156 ".*F_KFE": -0.8, # both front KFE
157 ".*H_KFE": 0.8, # both hind KFE
158 },
159 ),
160 actuators={"legs": ANYDRIVE_3_LSTM_ACTUATOR_CFG},
161 )
162
163
164##
165# Simulation Loop
166##
167
168
169def run_simulator(sim: SimulationContext, scene: InteractiveScene):
170 """Runs the simulation loop."""
171 # Extract scene entities
172 # note: we only do this here for readability.
173 rigid_object = scene["object"]
174 robot = scene["robot"]
175 # Define simulation stepping
176 sim_dt = sim.get_physics_dt()
177 count = 0
178 # Simulation loop
179 while simulation_app.is_running():
180 # Reset
181 if count % 500 == 0:
182 # reset counter
183 count = 0
184 # reset the scene entities
185 # object
186 root_state = rigid_object.data.default_root_state.clone()
187 root_state[:, :3] += scene.env_origins
188 rigid_object.write_root_state_to_sim(root_state)
189 # robot
190 # -- root state
191 root_state = robot.data.default_root_state.clone()
192 root_state[:, :3] += scene.env_origins
193 robot.write_root_state_to_sim(root_state)
194 # -- joint state
195 joint_pos, joint_vel = robot.data.default_joint_pos.clone(), robot.data.default_joint_vel.clone()
196 robot.write_joint_state_to_sim(joint_pos, joint_vel)
197 # clear internal buffers
198 scene.reset()
199 print("[INFO]: Resetting scene state...")
200
201 # Apply action to robot
202 robot.set_joint_position_target(robot.data.default_joint_pos)
203 # Write data to sim
204 scene.write_data_to_sim()
205 # Perform step
206 sim.step()
207 # Increment counter
208 count += 1
209 # Update buffers
210 scene.update(sim_dt)
211
212
213def main():
214 """Main function."""
215 # Load kit helper
216 sim_cfg = sim_utils.SimulationCfg(dt=0.005, device=args_cli.device)
217 sim = SimulationContext(sim_cfg)
218 # Set main camera
219 sim.set_camera_view([2.5, 0.0, 4.0], [0.0, 0.0, 2.0])
220
221 # Design scene
222 scene_cfg = MultiObjectSceneCfg(num_envs=args_cli.num_envs, env_spacing=2.0, replicate_physics=False)
223 with Timer("[INFO] Time to create scene: "):
224 scene = InteractiveScene(scene_cfg)
225
226 with Timer("[INFO] Time to randomize scene: "):
227 # DO YOUR OWN OTHER KIND OF RANDOMIZATION HERE!
228 # Note: Just need to acquire the right attribute about the property you want to set
229 # Here is an example on setting color randomly
230 randomize_shape_color(scene_cfg.object.prim_path)
231
232 # Play the simulator
233 sim.reset()
234 # Now we are ready!
235 print("[INFO]: Setup complete...")
236 # Run the simulator
237 run_simulator(sim, scene)
238
239
240if __name__ == "__main__":
241 # run the main execution
242 main()
243 # close sim app
244 simulation_app.close()
This script creates multiple environments, where each environment has a rigid object that is either a cone, a cube, or a sphere, and an articulation that is either the ANYmal-C or ANYmal-D robot.
Using Multi-Asset Spawning Functions#
It is possible to spawn different assets and USDs in each environment using the spawners
MultiAssetSpawnerCfg and MultiUsdFileCfg:
We set the spawn configuration in
RigidObjectCfgto beMultiAssetSpawnerCfg:object: RigidObjectCfg = RigidObjectCfg( prim_path="/World/envs/env_.*/Object", spawn=sim_utils.MultiAssetSpawnerCfg( assets_cfg=[ sim_utils.ConeCfg( radius=0.3, height=0.6, visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.0, 1.0, 0.0), metallic=0.2), ), sim_utils.CuboidCfg( size=(0.3, 0.3, 0.3), visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(1.0, 0.0, 0.0), metallic=0.2), ), sim_utils.SphereCfg( radius=0.3, visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.0, 0.0, 1.0), metallic=0.2), ), ], random_choice=True, rigid_props=sim_utils.RigidBodyPropertiesCfg( solver_position_iteration_count=4, solver_velocity_iteration_count=0 ), mass_props=sim_utils.MassPropertiesCfg(mass=1.0), collision_props=sim_utils.CollisionPropertiesCfg(), ), init_state=RigidObjectCfg.InitialStateCfg(pos=(0.0, 0.0, 2.0)), )
This function allows you to define a list of different assets that can be spawned as rigid objects. When
random_choiceis set to True, one asset from the list is randomly selected and spawned at the specified prim path.Similarly, we set the spawn configuration in
ArticulationCfgto beMultiUsdFileCfg:robot: ArticulationCfg = ArticulationCfg( prim_path="/World/envs/env_.*/Robot", spawn=sim_utils.MultiUsdFileCfg( usd_path=[ f"{ISAACLAB_NUCLEUS_DIR}/Robots/ANYbotics/ANYmal-C/anymal_c.usd", f"{ISAACLAB_NUCLEUS_DIR}/Robots/ANYbotics/ANYmal-D/anymal_d.usd", ], random_choice=True, rigid_props=sim_utils.RigidBodyPropertiesCfg( disable_gravity=False, retain_accelerations=False, linear_damping=0.0, angular_damping=0.0, max_linear_velocity=1000.0, max_angular_velocity=1000.0, max_depenetration_velocity=1.0, ), articulation_props=sim_utils.ArticulationRootPropertiesCfg( enabled_self_collisions=True, solver_position_iteration_count=4, solver_velocity_iteration_count=0 ), activate_contact_sensors=True, ), init_state=ArticulationCfg.InitialStateCfg( pos=(0.0, 0.0, 0.6), joint_pos={ ".*HAA": 0.0, # all HAA ".*F_HFE": 0.4, # both front HFE ".*H_HFE": -0.4, # both hind HFE ".*F_KFE": -0.8, # both front KFE ".*H_KFE": 0.8, # both hind KFE }, ), actuators={"legs": ANYDRIVE_3_LSTM_ACTUATOR_CFG}, )
Similar to before, this configuration allows the selection of different USD files representing articulated assets.
Things to Note#
Similar asset structuring#
While spawning and handling multiple assets using the same physics interface (the rigid object or articulation classes), it is essential to have the assets at all the prim locations follow a similar structure. In case of an articulation, this means that they all must have the same number of links and joints, the same number of collision bodies and the same names for them. If that is not the case, the physics parsing of the prims can get affected and fail.
The main purpose of this functionality is to enable the user to create randomized versions of the same asset, for example robots with different link lengths, or rigid objects with different collider shapes.
Disabling physics replication in interactive scene#
By default, the flag scene.InteractiveScene.replicate_physics is set to True. This flag informs the physics
engine that the simulation environments are copies of one another so it just needs to parse the first environment
to understand the entire simulation scene. This helps speed up the simulation scene parsing.
However, in the case of spawning different assets in different environments, this assumption does not hold
anymore. Hence the flag scene.InteractiveScene.replicate_physics must be disabled.
# Design scene
scene_cfg = MultiObjectSceneCfg(num_envs=args_cli.num_envs, env_spacing=2.0, replicate_physics=False)
with Timer("[INFO] Time to create scene: "):
scene = InteractiveScene(scene_cfg)
The Code Execution#
To execute the script with multiple environments and randomized assets, use the following command:
./isaaclab.sh -p source/standalone/demos/multi_asset.py --num_envs 2048
This command runs the simulation with 2048 environments, each with randomly selected assets.
To stop the simulation, you can close the window, or press Ctrl+C in the terminal.