Using the Interactive Scene

Using the Interactive Scene#

So far in the tutorials, we manually spawned assets into the simulation and created object instances to interact with them. However, as the complexity of the scene increases, it becomes tedious to perform these tasks manually. In this tutorial, we will introduce the scene.InteractiveScene class, which provides a convenient interface for spawning prims and managing them in the simulation.

At a high-level, the interactive scene is a collection of scene entities. Each entity can be either a non-interactive prim (e.g. ground plane, light source), an interactive prim (e.g. articulation, rigid object), or a sensor (e.g. camera, lidar). The interactive scene provides a convenient interface for spawning these entities and managing them in the simulation.

Compared the manual approach, it provides the following benefits:

  • Alleviates the user needing to spawn each asset separately as this is handled implicitly.

  • Enables user-friendly cloning of scene prims for multiple environments.

  • Collects all the scene entities into a single object, which makes them easier to manage.

In this tutorial, we take the cartpole example from the Interacting with an articulation tutorial and replace the design_scene function with an scene.InteractiveScene object. While it may seem like overkill to use the interactive scene for this simple example, it will become more useful in the future as more assets and sensors are added to the scene.

The Code#

This tutorial corresponds to the create_scene.py script within scripts/tutorials/02_scene.

Code for create_scene.py
  1# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
  2# All rights reserved.
  3#
  4# SPDX-License-Identifier: BSD-3-Clause
  5
  6"""This script demonstrates how to use the interactive scene interface to setup a scene with multiple prims.
  7
  8.. code-block:: bash
  9
 10    # Usage
 11    ./isaaclab.sh -p scripts/tutorials/02_scene/create_scene.py --num_envs 32
 12
 13"""
 14
 15"""Launch Isaac Sim Simulator first."""
 16
 17
 18import argparse
 19
 20from isaaclab.app import AppLauncher
 21
 22# add argparse arguments
 23parser = argparse.ArgumentParser(description="Tutorial on using the interactive scene interface.")
 24parser.add_argument("--num_envs", type=int, default=2, help="Number of environments to spawn.")
 25# append AppLauncher cli args
 26AppLauncher.add_app_launcher_args(parser)
 27# parse the arguments
 28args_cli = parser.parse_args()
 29
 30# launch omniverse app
 31app_launcher = AppLauncher(args_cli)
 32simulation_app = app_launcher.app
 33
 34"""Rest everything follows."""
 35
 36import torch
 37import warp as wp
 38
 39import isaaclab.sim as sim_utils
 40from isaaclab.assets import ArticulationCfg, AssetBaseCfg
 41from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
 42from isaaclab.sim import SimulationContext
 43from isaaclab.utils import configclass
 44
 45##
 46# Pre-defined configs
 47##
 48from isaaclab_assets import CARTPOLE_CFG  # isort:skip
 49
 50
 51@configclass
 52class CartpoleSceneCfg(InteractiveSceneCfg):
 53    """Configuration for a cart-pole scene."""
 54
 55    # ground plane
 56    ground = AssetBaseCfg(prim_path="/World/defaultGroundPlane", spawn=sim_utils.GroundPlaneCfg())
 57
 58    # lights
 59    dome_light = AssetBaseCfg(
 60        prim_path="/World/Light", spawn=sim_utils.DomeLightCfg(intensity=3000.0, color=(0.75, 0.75, 0.75))
 61    )
 62
 63    # articulation
 64    cartpole: ArticulationCfg = CARTPOLE_CFG.replace(prim_path="{ENV_REGEX_NS}/Robot")
 65
 66
 67def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
 68    """Runs the simulation loop."""
 69    # Extract scene entities
 70    # note: we only do this here for readability.
 71    robot = scene["cartpole"]
 72    # Define simulation stepping
 73    sim_dt = sim.get_physics_dt()
 74    count = 0
 75    # Simulation loop
 76    while simulation_app.is_running():
 77        # Reset
 78        if count % 500 == 0:
 79            # reset counter
 80            count = 0
 81            # reset the scene entities
 82            # root state
 83            # we offset the root state by the origin since the states are written in simulation world frame
 84            # if this is not done, then the robots will be spawned at the (0, 0, 0) of the simulation world
 85            root_pose = wp.to_torch(robot.data.default_root_pose).clone()
 86            root_pose[:, :3] += scene.env_origins
 87            robot.write_root_pose_to_sim_index(root_pose=root_pose)
 88            root_vel = wp.to_torch(robot.data.default_root_vel).clone()
 89            robot.write_root_velocity_to_sim_index(root_velocity=root_vel)
 90            # set joint positions with some noise
 91            joint_pos, joint_vel = (
 92                wp.to_torch(robot.data.default_joint_pos).clone(),
 93                wp.to_torch(robot.data.default_joint_vel).clone(),
 94            )
 95            joint_pos += torch.rand_like(joint_pos) * 0.1
 96            robot.write_joint_position_to_sim_index(position=joint_pos)
 97            robot.write_joint_velocity_to_sim_index(velocity=joint_vel)
 98            # clear internal buffers
 99            scene.reset()
100            print("[INFO]: Resetting robot state...")
101        # Apply random action
102        # -- generate random joint efforts
103        efforts = torch.randn_like(wp.to_torch(robot.data.joint_pos)) * 5.0
104        # -- apply action to the robot
105        robot.set_joint_effort_target_index(target=efforts)
106        # -- write data to sim
107        scene.write_data_to_sim()
108        # Perform step
109        sim.step()
110        # Increment counter
111        count += 1
112        # Update buffers
113        scene.update(sim_dt)
114
115
116def main():
117    """Main function."""
118    # Load kit helper
119    sim_cfg = sim_utils.SimulationCfg(device=args_cli.device)
120    sim = SimulationContext(sim_cfg)
121    # Set main camera
122    sim.set_camera_view([2.5, 0.0, 4.0], [0.0, 0.0, 2.0])
123    # Design scene
124    scene_cfg = CartpoleSceneCfg(num_envs=args_cli.num_envs, env_spacing=2.0)
125    scene = InteractiveScene(scene_cfg)
126    # Play the simulator
127    sim.reset()
128    # Now we are ready!
129    print("[INFO]: Setup complete...")
130    # Run the simulator
131    run_simulator(sim, scene)
132
133
134if __name__ == "__main__":
135    # run the main function
136    main()
137    # close sim app
138    simulation_app.close()

The Code Explained#

While the code is similar to the previous tutorial, there are a few key differences that we will go over in detail.

Scene configuration#

The scene is composed of a collection of entities, each with their own configuration. These are specified in a configuration class that inherits from scene.InteractiveSceneCfg. The configuration class is then passed to the scene.InteractiveScene constructor to create the scene.

For the cartpole example, we specify the same scene as in the previous tutorial, but list them now in the configuration class CartpoleSceneCfg instead of manually spawning them.

@configclass
class CartpoleSceneCfg(InteractiveSceneCfg):
    """Configuration for a cart-pole scene."""

    # ground plane
    ground = AssetBaseCfg(prim_path="/World/defaultGroundPlane", spawn=sim_utils.GroundPlaneCfg())

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

    # articulation
    cartpole: ArticulationCfg = CARTPOLE_CFG.replace(prim_path="{ENV_REGEX_NS}/Robot")

The variable names in the configuration class are used as keys to access the corresponding entity from the scene.InteractiveScene object. For example, the cartpole can be accessed via scene["cartpole"]. However, we will get to that later. First, let’s look at how individual scene entities are configured.

Similar to how a rigid object and articulation were configured in the previous tutorials, the configurations are specified using a configuration class. However, there is a key difference between the configurations for the ground plane and light source and the configuration for the cartpole. The ground plane and light source are non-interactive prims, while the cartpole is an interactive prim. This distinction is reflected in the configuration classes used to specify them. The configurations for the ground plane and light source are specified using an instance of the assets.AssetBaseCfg class while the cartpole is configured using an instance of the assets.ArticulationCfg. Anything that is not an interactive prim (i.e., neither an asset nor a sensor) is not handled by the scene during simulation steps.

Another key difference to note is in the specification of the prim paths for the different prims:

  • Ground plane: /World/defaultGroundPlane

  • Light source: /World/Light

  • Cartpole: {ENV_REGEX_NS}/Robot

As we learned earlier, Omniverse creates a graph of prims in the USD stage. The prim paths are used to specify the location of the prim in the graph. The ground plane and light source are specified using absolute paths, while the cartpole is specified using a relative path. The relative path is specified using the ENV_REGEX_NS variable, which is a special variable that is replaced with the environment name during scene creation. Any entity that has the ENV_REGEX_NS variable in its prim path will be cloned for each environment. This path is replaced by the scene object with /World/envs/env_{i} where i is the environment index.

Scene instantiation#

Unlike before where we called the design_scene function to create the scene, we now create an instance of the scene.InteractiveScene class and pass in the configuration object to its constructor. While creating the configuration instance of CartpoleSceneCfg we specify how many environment copies we want to create using the num_envs argument. This will be used to clone the scene for each environment.

    # Design scene
    scene_cfg = CartpoleSceneCfg(num_envs=args_cli.num_envs, env_spacing=2.0)
    scene = InteractiveScene(scene_cfg)

Accessing scene elements#

Similar to how entities were accessed from a dictionary in the previous tutorials, the scene elements can be accessed from the InteractiveScene object using the [] operator. The operator takes in a string key and returns the corresponding entity. The key is specified through the configuration class for each entity. For example, the cartpole is specified using the key "cartpole" in the configuration class.

    # Extract scene entities
    # note: we only do this here for readability.
    robot = scene["cartpole"]

Running the simulation loop#

The rest of the script looks similar to previous scripts that interfaced with assets.Articulation, with a few small differences in the methods called:

Under the hood, the methods of scene.InteractiveScene call the corresponding methods of the entities in the scene.

The Code Execution#

Let’s run the script to simulate 32 cartpoles in the scene. We can do this by passing the --num_envs argument to the script.

./isaaclab.sh -p scripts/tutorials/02_scene/create_scene.py --num_envs 32

This should open a stage with 32 cartpoles swinging around randomly. You can use the mouse to rotate the camera and the arrow keys to move around the scene.

result of create_scene.py

In this tutorial, we saw how to use scene.InteractiveScene to create a scene with multiple assets. We also saw how to use the num_envs argument to clone the scene for multiple environments.

There are many more example usages of the scene.InteractiveSceneCfg in the tasks found under the isaaclab_tasks extension. Please check out the source code to see how they are used for more complex scenes.