# Cross-Simulator Support

MetaSim enables you to write code once and run it across multiple physics simulators without modifications. This is one of the core features that makes RoboVerse a unified platform for robot learning.

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## Supported Simulators

| Simulator | Backend | GPU Parallel | Best Use Case |
|-----------|---------|--------------|---------------|
| `mujoco` | MuJoCo | Via MJX | Fast prototyping, CPU training |
| `mjx` | MuJoCo MJX | Native | Massively parallel RL |
| `isaacsim` | Isaac Sim | Native | High-fidelity sim2real |
| `isaacgym` | Isaac Gym | Native | GPU-accelerated RL |
| `sapien3` | SAPIEN 3 | Native | Manipulation research |
| `sapien2` | SAPIEN 2 | - | Legacy support |
| `genesis` | Genesis | Native | Large-scale training |
| `pybullet` | PyBullet | - | Debugging, education |

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## Basic Usage

### Switching Simulators

Change the simulator by setting the `simulator` parameter in your scenario:

```python
from metasim.scenario.scenario import ScenarioCfg

# Run with MuJoCo
scenario = ScenarioCfg(
    robots=["franka"],
    simulator="mujoco",  # Change this to switch simulators
    num_envs=1,
)

# Or switch to Isaac Sim
scenario = ScenarioCfg(
    robots=["franka"],
    simulator="isaacsim",
    num_envs=1,
)
```

### Command Line Examples

Most scripts support the `--sim` argument to select the simulator:

```bash
# Run with MuJoCo
python scripts/advanced/replay_demo.py --sim=mujoco --task=StackCube

# Run with Isaac Gym
python scripts/advanced/replay_demo.py --sim=isaacgym --task=StackCube

# Run with SAPIEN 3
python scripts/advanced/replay_demo.py --sim=sapien3 --task=PickCube
```

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## Considerations

### Feature Parity

Not all features are available across all simulators. Check the [Support Matrix](support_matrix.rst) for detailed compatibility information.