Isaac Sim Headless Usage (--no-window)

This skill covers headless usage of a built or installed Isaac Sim. It does not cover Docker images, container orchestration, or CI/CD wiring — those live with the deployment infrastructure that wraps Isaac Sim, not in this skill.

Launch modes

1. Headed (Default)

./isaac-sim.sh
# Launches isaacsim.exp.full.kit with full UI

2. Headless with Rendering

For headless GPU rendering (generates images without a window):

# Native headless — uses EGL/Vulkan offscreen
./isaac-sim.sh --no-window

# With explicit display (required on some systems)
DISPLAY=:0 ./isaac-sim.sh --no-window

3. Headless No Rendering

For physics-only simulation (no viewport, no rendering):

./isaac-sim.sh --no-window --/app/renderer/enabled=false

4. Python Standalone Scripts

Run simulation logic from a standalone Python script:

./python.sh my_simulation.py
# Uses Isaac Sim's Python environment with all extensions available

The script controls headless behavior via the SimulationApp config (see Batch simulation pattern below) — python.sh does not need a --no-window flag.

5. Kit CLI with Script Execution

[Code: scripts/kit_cli_with_script_execution.sh]

Key CLI Flags

App Configurations

Batch Simulation Pattern

The canonical headless bootstrap pattern lives in:

• source/standalone_examples/api/isaacsim.simulation_app/hello_world.py (minimal)
• source/standalone_examples/api/isaacsim.simulation_app/load_stage.py (stage open + step loop with --test mode)

For an N-episode batch driver, wrap that bootstrap in a Python for episode in range(N) loop. Use the current APIs:

• isaacsim.core.experimental.utils.stage for stage open / waiting on load
• isaacsim.core.simulation_manager.SimulationManager.setup_simulation(dt=..., device=...) to configure physics
• isaacsim.core.experimental.utils.app (enable_extension, play, stop, update_app) to drive the loop

Skeleton (paraphrased from load_stage.py, adapted for batch):

from isaacsim import SimulationApp

simulation_app = SimulationApp({"headless": True, "renderer": "RayTracedLighting"})

import isaacsim.core.experimental.utils.app as app_utils
import isaacsim.core.experimental.utils.stage as stage_utils
from isaacsim.core.simulation_manager import SimulationManager

NUM_EPISODES, STEPS_PER_EPISODE = 100, 1000
for episode in range(NUM_EPISODES):
    stage_utils.open_stage("/path/to/scene.usd")
    while stage_utils.is_stage_loading():
        simulation_app.update()
    SimulationManager.setup_simulation(dt=1.0 / 60.0, device="cpu")
    app_utils.play()
    for _ in range(STEPS_PER_EPISODE):
        simulation_app.update()
    app_utils.stop()

simulation_app.close()

Avoid the legacy isaacsim.core.api.World / isaacsim.core.utils.stage paths — they are deprecated in Kit 110.

Migration: see Renaming Extensions for the omni.isaac.* → isaacsim.* map covering omni.isaac.core, omni.isaac.utils, and friends.

Performance Tuning for Batch/Headless

Physics-Only (Fastest)

config = {"headless": True, "renderer": None}
# In step loop:
world.step(render=False)

Throughput: 10-50x real-time depending on scene complexity.

Memory Management

• Clear stage between episodes: world.clear() + garbage collect
• Use instanceable assets: make_instanceable: true in config.yaml
• Monitor GPU memory: nvidia-smi — Kit leaks if stages aren't properly cleared
• GB10 (Jetson): Max ~35K prims, 16GB shared memory — reduce scene complexity

Known Issues (Kit 110)

• DISPLAY=:0 required for headless viewport on Kit 110 with complex stages on some GPU configurations
• Viewport never initializes without DISPLAY on some configurations — use --no-window + offscreen rendering
• CUDA OOM: Monitor with nvidia-smi, keep under 90% GPU VRAM utilization
• Startup time: ~30-60s cold start; use persistent processes for interactive batch
• Newton physics + torch conflict: Never import torch before physics settle