Creating a simulation scene#
This tutorial shows how to create a basic simulation scene using SimulationManager. It covers the setup of the simulation context, adding rigid objects, and running the simulation loop.
The Code#
The tutorial corresponds to the create_scene.py script in the scripts/tutorials/sim directory.
Code for create_scene.py
1# ----------------------------------------------------------------------------
2# Copyright (c) 2021-2025 DexForce Technology Co., Ltd.
3#
4# Licensed under the Apache License, Version 2.0 (the "License");
5# you may not use this file except in compliance with the License.
6# You may obtain a copy of the License at
7#
8# http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS,
12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15# ----------------------------------------------------------------------------
16
17"""
18This script demonstrates how to create a simulation scene using SimulationManager.
19It shows the basic setup of simulation context, adding objects, and sensors.
20"""
21
22import argparse
23import time
24
25from embodichain.lab.sim import SimulationManager, SimulationManagerCfg
26from embodichain.lab.sim.cfg import RigidBodyAttributesCfg
27from embodichain.lab.sim.shapes import CubeCfg, MeshCfg
28from embodichain.lab.sim.objects import RigidObject, RigidObjectCfg
29from dexsim.utility.path import get_resources_data_path
30
31
32def main():
33 """Main function to create and run the simulation scene."""
34
35 # Parse command line arguments
36 parser = argparse.ArgumentParser(
37 description="Create a simulation scene with SimulationManager"
38 )
39 parser.add_argument(
40 "--headless",
41 action="store_true",
42 default=False,
43 help="Run simulation in headless mode",
44 )
45 parser.add_argument(
46 "--num_envs", type=int, default=1, help="Number of parallel environments"
47 )
48 parser.add_argument(
49 "--device", type=str, default="cpu", help="Simulation device (cuda or cpu)"
50 )
51 parser.add_argument(
52 "--enable_rt",
53 action="store_true",
54 default=False,
55 help="Enable ray tracing for better visuals",
56 )
57 args = parser.parse_args()
58
59 # Configure the simulation
60 sim_cfg = SimulationManagerCfg(
61 width=1920,
62 height=1080,
63 headless=True,
64 physics_dt=1.0 / 100.0, # Physics timestep (100 Hz)
65 sim_device=args.device,
66 enable_rt=args.enable_rt, # Enable ray tracing for better visuals
67 num_envs=args.num_envs,
68 arena_space=3.0,
69 )
70
71 # Create the simulation instance
72 sim = SimulationManager(sim_cfg)
73
74 # Add objects to the scene
75 cube: RigidObject = sim.add_rigid_object(
76 cfg=RigidObjectCfg(
77 uid="cube",
78 shape=CubeCfg(size=[0.1, 0.1, 0.1]),
79 body_type="dynamic",
80 attrs=RigidBodyAttributesCfg(
81 mass=1.0,
82 dynamic_friction=0.5,
83 static_friction=0.5,
84 restitution=0.1,
85 ),
86 init_pos=[0.0, 0.0, 1.0],
87 )
88 )
89
90 print("[INFO]: Scene setup complete!")
91 print(f"[INFO]: Running simulation with {args.num_envs} environment(s)")
92 print("[INFO]: Press Ctrl+C to stop the simulation")
93
94 # Open window when the scene has been set up
95 if not args.headless:
96 sim.open_window()
97
98 # Run the simulation
99 run_simulation(sim)
100
101
102def run_simulation(sim: SimulationManager):
103 """Run the simulation loop.
104
105 Args:
106 sim: The SimulationManager instance to run
107 """
108
109 # Initialize GPU physics if using CUDA
110 if sim.is_use_gpu_physics:
111 sim.init_gpu_physics()
112
113 step_count = 0
114
115 try:
116 last_time = time.time()
117 last_step = 0
118 while True:
119 # Update physics simulation
120 sim.update(step=1)
121 step_count += 1
122
123 # Print FPS every second
124 if step_count % 100 == 0:
125 current_time = time.time()
126 elapsed = current_time - last_time
127 fps = (
128 sim.num_envs * (step_count - last_step) / elapsed
129 if elapsed > 0
130 else 0
131 )
132 print(f"[INFO]: Simulation step: {step_count}, FPS: {fps:.2f}")
133 last_time = current_time
134 last_step = step_count
135
136 except KeyboardInterrupt:
137 print("\n[INFO]: Stopping simulation...")
138 finally:
139 # Clean up resources
140 sim.destroy()
141 print("[INFO]: Simulation terminated successfully")
142
143
144if __name__ == "__main__":
145 main()
The Code Explained#
Configuring the simulation#
The first step is to configure the simulation environment. This is done using the SimulationManagerCfg data class, which allows you to specify various parameters like window dimensions, headless mode, physics timestep, simulation device (CPU/GPU), and rendering options like ray tracing.
Command-line arguments are parsed using argparse to allow for easy customization of the simulation from the terminal.
# Parse command line arguments
parser = argparse.ArgumentParser(
description="Create a simulation scene with SimulationManager"
)
parser.add_argument(
"--headless",
action="store_true",
default=False,
help="Run simulation in headless mode",
)
parser.add_argument(
"--num_envs", type=int, default=1, help="Number of parallel environments"
)
parser.add_argument(
"--device", type=str, default="cpu", help="Simulation device (cuda or cpu)"
)
parser.add_argument(
"--enable_rt",
action="store_true",
default=False,
help="Enable ray tracing for better visuals",
)
args = parser.parse_args()
# Configure the simulation
sim_cfg = SimulationManagerCfg(
width=1920,
height=1080,
headless=True,
physics_dt=1.0 / 100.0, # Physics timestep (100 Hz)
sim_device=args.device,
enable_rt=args.enable_rt, # Enable ray tracing for better visuals
num_envs=args.num_envs,
arena_space=3.0,
)
# Create the simulation instance
sim = SimulationManager(sim_cfg)
There are two kinds of physics mode in SimulationManager:
manual: The physics updates only when the user calls the
SimulationManager.update()function. This mode is used for robot learning tasks where precise control over simulation steps is required. Enabled by settingSimulationManager.set_manual_update()to True.auto: The physics updates in a standalone thread, which enable asynchronous rendering and physics stepping. This mode is suitable for visualizations and demos for digital twins applications. This is the default mode.
Adding objects to the scene#
With the simulation context created, we can add objects. This tutorial demonstrates adding a dynamic rigid cube to the scene using the SimulationManager.add_rigid_object() method. The object’s properties, such as its shape, initial position, and physics attributes (mass, friction, restitution), are defined through a configuration object, cfg.RigidObjectCfg.
# Add objects to the scene
cube: RigidObject = sim.add_rigid_object(
cfg=RigidObjectCfg(
uid="cube",
shape=CubeCfg(size=[0.1, 0.1, 0.1]),
body_type="dynamic",
attrs=RigidBodyAttributesCfg(
mass=1.0,
dynamic_friction=0.5,
static_friction=0.5,
restitution=0.1,
),
init_pos=[0.0, 0.0, 1.0],
Running the simulation#
The simulation is advanced through a loop in the run_simulation function. Before starting the loop, GPU physics is initialized if a CUDA device is used.
Inside the loop, SimulationManager.update() is called to step the physics simulation forward. The script also includes logic to calculate and print the Frames Per Second (FPS) to monitor performance. The simulation runs until it’s manually stopped with Ctrl+C.
def run_simulation(sim: SimulationManager):
"""Run the simulation loop.
Args:
sim: The SimulationManager instance to run
"""
# Initialize GPU physics if using CUDA
if sim.is_use_gpu_physics:
sim.init_gpu_physics()
step_count = 0
try:
last_time = time.time()
last_step = 0
while True:
# Update physics simulation
sim.update(step=1)
step_count += 1
# Print FPS every second
if step_count % 100 == 0:
current_time = time.time()
elapsed = current_time - last_time
fps = (
sim.num_envs * (step_count - last_step) / elapsed
if elapsed > 0
else 0
)
print(f"[INFO]: Simulation step: {step_count}, FPS: {fps:.2f}")
last_time = current_time
last_step = step_count
Exiting the simulation#
Upon exiting the simulation loop (e.g., by a KeyboardInterrupt), it’s important to clean up resources. The SimulationManager.destroy() method is called in a finally block to ensure that the simulation is properly terminated and all allocated resources are released.
except KeyboardInterrupt:
print("\n[INFO]: Stopping simulation...")
finally:
# Clean up resources
sim.destroy()
The Code Execution#
To run the script and see the result, execute the following command:
python scripts/tutorials/sim/create_scene.py
A window should appear showing a cube dropping onto a flat plane. To stop the simulation, you can either close the window or press Ctrl+C in the terminal.
You can also pass arguments to customize the simulation. For example, to run in headless mode with n parallel environments using specified device:
python scripts/tutorials/sim/create_scene.py --headless --num_envs <n> --device <cuda/cpu>
Now that we have a basic understanding of how to create a scene, let’s move on to more advanced topics.