Skip to content

Simple Sim

Simple Sim is a lightweight 2D/3D simulator for basic testing and development when full Isaac Sim fidelity isn't needed.

Overview

Simple Sim provides a faster, more resource-efficient alternative to Isaac Sim for:

  • Quick algorithm prototyping - Faster iteration cycles
  • CI/CD testing - Lightweight enough for automated testing pipelines
  • Lower hardware requirements - Works on systems without high-end GPUs
  • Basic flight dynamics - Sufficient for many planning and control algorithms

Trade-offs:

  • ✅ Faster startup and execution
  • ✅ Lower computational requirements
  • ✅ Simpler scene setup
  • ❌ Less realistic physics
  • ❌ Limited sensor simulation
  • ❌ Basic graphics (no photorealism)

Use Cases

Algorithm Development

Test planning and control algorithms without full simulation overhead:

airstack up simple-sim robot

Your ROS 2 autonomy stack connects to Simple Sim just like Isaac Sim.

Continuous Integration

Run automated tests in CI pipelines:

# In CI script
airstack up --profile simple simple-robot
# Run tests...
airstack down

Resource-Constrained Environments

Develop on laptops or systems without high-end GPUs:

  • Works with integrated graphics
  • Lower RAM requirements (~4GB vs 16GB+)
  • Faster container startup

Architecture

Simple Sim is built on:

  • ROS 2 native - Direct ROS 2 integration
  • Lightweight physics - Basic dynamics simulation
  • 2D/3D visualization - RViz-compatible
  • Configurable dynamics - Tune flight characteristics

Comparison with Isaac Sim

Feature Isaac Sim Simple Sim
Graphics Photorealistic raytracing Basic 3D rendering
Physics NVIDIA PhysX (high-fidelity) Simplified dynamics
Sensors Full suite (cameras, LiDAR, etc.) Basic sensors
Startup time 30-60 seconds 5-10 seconds
GPU requirements RTX 3070+ Integrated graphics OK
RAM requirements 16GB+ 4GB+
Scene authoring USD format (Omniverse) Configuration files
Multi-robot Full support Full support

Quick Start

Launch Simple Sim

# Launch Simple Sim only
airstack up --profile simple simple-sim

# Launch with robot stack
airstack up --profile simple simple-robot

Verify Connection

# Check ROS 2 topics
docker exec airstack-simple-robot-1 bash -c "ros2 topic list | grep simple"

Configuration

Simple Sim configuration is in simulation/simple-sim/ros_ws/:

simulation/simple-sim/
├── docker/                    # Docker configuration
│   ├── docker-compose.yaml
│   └── Dockerfile.sim
├── models/                    # 3D models
│   └── download.sh            # Model download script
└── ros_ws/                    # Simple Sim ROS workspace
    └── src/
        └── sim/               # Simulator package
            ├── config/        # Configuration files
            └── launch/        # Launch files

Customizing Flight Dynamics

Edit configuration in simulation/simple-sim/ros_ws/src/sim/config/:

# Example: drone dynamics parameters
mass: 1.5  # kg
max_thrust: 20.0  # N
drag_coefficient: 0.1

Development Workflow

Testing Algorithm Changes

  1. Start Simple Sim: 

    airstack up --profile simple simple-robot

  2. Make changes to autonomy code on host

  3. Rebuild in container: 

    docker exec airstack-simple-robot-1 bash -c "bws --packages-select my_planner"

  4. Test immediately (faster than Isaac Sim restart)

Transitioning to Isaac Sim

Once algorithms work in Simple Sim, test in Isaac Sim:

# Stop Simple Sim
airstack down

# Start Isaac Sim
airstack up robot isaac-sim

Code changes are minimal - same ROS 2 topics and interfaces.

Limitations

What Simple Sim can't do:

  • Photorealistic rendering
  • Complex sensor simulation (cameras, LiDAR)
  • Accurate aerodynamic effects
  • Detailed collision physics
  • Custom 3D environments (limited to basic models)

When to use Isaac Sim instead:

  • Visual perception algorithm development
  • Realistic sensor simulation needed
  • Complex environment interactions
  • Final validation before hardware deployment

See Also