Real-Time Factor Significantly Slower When Running Isaac Sim as Standalone Python Script

Omniverse Isaac Sim
1

Hello everyone,

I’ve been experiencing a significant slowdown in the real-time factor when running my Isaac Sim simulation as a standalone Python script compared to running it directly through the Isaac Sim GUI. Specifically:

  • With GUI: real_time_factor = 0.6
  • As a standalone Python script: real_time_factor = 0.3

This is a simplified version of the script I’m running:

import argparse
from utils.file_operations import read_yaml

# ---------------------------------------------------------------------------- #
#                       Read the YAML configuration file                       #
# ---------------------------------------------------------------------------- #
parser = argparse.ArgumentParser()
parser.add_argument("--config_file", help="Path to the configuration file", default="config/params.yaml")
args = parser.parse_args()

config = read_yaml(args.config_file)

# ---------------------------------------------------------------------------- #
#                            Start The SimulationApp                           #
# ---------------------------------------------------------------------------- #
import isaacsim
from omni.isaac.kit import SimulationApp

simulation_app = SimulationApp(launch_config=config.launch_config)

import warnings

import omni.client
import omni.kit.commands
import omni.kit.app
import omni.timeline
import omni.usd

from omni.isaac.core import World
from omni.isaac.core.utils.stage import is_stage_loading
from omni.isaac.core.utils.extensions import enable_extension

# Enable ROS2 bridge extension
enable_extension("omni.isaac.ros2_bridge")
simulation_app.update()

import rclpy
from rclpy.node import Node
from rclpy.parameter import Parameter

warnings.filterwarnings("ignore")

class IsaacSim(Node):
    def __init__(self):
        super().__init__('IsaacSim')
                
        # Set sim time to true
        self.set_parameters([Parameter('use_sim_time', Parameter.Type.BOOL, True)])
        
        omni.usd.get_context().open_stage("/home/lukas/git_clones/isaac-simulation-ros/usd_files/2024_09_05_robot_demo_space.usd")
        
        # wait two frames so that stage starts loading
        simulation_app.update()
        simulation_app.update()

        print("Loading stage...")
        while is_stage_loading():
            simulation_app.update()
        print("Loading Complete")
        
        
        self.world = World(stage_units_in_meters=1.0)
        self.world.reset()
        

    def run_simulation(self):
        while simulation_app.is_running():
            self.world.step(render=True)

            # deal with pause/stop
            if self.world.is_playing():
                if self.world.current_time_step_index == 0:
                    self.world.reset()

        simulation_app.close()
        
        
def main():
    rclpy.init()

    isaac_sim = IsaacSim()
    isaac_sim.run_simulation()
    
    rclpy.shutdown()

if __name__ == '__main__':
    main()

System Specs:

  • GPU: RTX 4080 Super
  • CPU: AMD Ryzen 9 7950X 16-Core Processor
  • RAM: 64 GB
  • OS: Ubuntu 22.04
  • Isaac Sim Version: 4.1.0 (running in Docker)

I’ve tried various suggestions from other forum posts to increase the real-time factor when running as a standalone python script, but nothing has made a significant difference.

Attached you can find a video where I start Isaac-sim.sh and open the USD, and afterwards, I use the Python script to load the USD and start the simulation. The real-time factors of both can be compared by looking at the wall time in RVIZ.

Has anyone else encountered this issue? Any advice or insights into why the standalone script is performing so much slower would be greatly appreciated!

Thank you!

1 Like
2

I still don’t understand why the standalone script is much slower then running Isaac Sim from the GUI. Any ideas?

4

Hi @lukas-bergs , thank you for sharing the script. Is there a reason why the simulation run is being called through a ROS node? You should be able to start up Isaac Sim, enable the ROS bridge in the script and use the Real Time Factor OmniGraph node directly. Please let us know if you observe a discrepancy there with the repro steps too.

5

Hi @rchadha,

Thanks for the response!

I removed the ROS node from the simulation run and added the RTF OmniGraph node, but unfortunately, there’s no difference.

  • With GUI: real_time_factor = 0.6
  • As a standalone Python script: real_time_factor = 0.3

Could you provide further assistance?

6

Hi @rchadha,
is there anything else that I can try?
Best regards,
Lukas

1 Like