# PyBullet Simulation

Running the GPS-denied drone simulation with PyBullet.

## Standalone Mode (Recommended)

No ROS 2 required! Single terminal:

```bash
source activate.sh
python standalone_simulation.py --pattern circular --speed 0.3
```

### Options

```bash
python standalone_simulation.py --help

Options:
  --pattern, -p   stationary, linear, circular, square
  --speed, -s     Rover speed in m/s (default: 0.5)
  --amplitude, -a Movement amplitude in meters (default: 2.0)
```

---

## ROS 2 Mode (2 Terminals)

For distributed or remote simulation:

**Terminal 1 - Simulator:**
```bash
source activate.sh
python simulation_host.py
```

**Terminal 2 - Controllers:**
```bash
source activate.sh
python run_bridge.py --pattern circular --speed 0.3
```

### Remote Setup

Run simulator on one machine, controllers on another:

**Machine 1 (with display):**
```bash
python simulation_host.py  # Listens on 0.0.0.0:5555
```

**Machine 2 (headless):**
```bash
python run_bridge.py --host 192.168.1.100 --pattern circular
```

---

## Building Standalone Executable

Create a distributable executable:

```bash
source activate.sh

# Build standalone simulation (recommended)
python build_exe.py

# Build simulation_host
python build_exe.py simulation_host

# Build all
python build_exe.py all
```

Executables are created in `dist/`.

---

## Simulation Parameters

| Parameter | Value |
|-----------|-------|
| Physics Rate | 240 Hz |
| Telemetry Rate | 24 Hz |
| Drone Mass | 1.0 kg |
| UDP Port | 5555 (commands), 5556 (telemetry) |

## GPS-Denied Sensors

| Sensor | Description |
|--------|-------------|
| IMU | Orientation, angular velocity |
| Altimeter | Barometric altitude, vertical velocity |
| Velocity | Optical flow estimate |
| Camera | 320x240 downward JPEG image |
| Landing Pad | Vision-based relative position |

## Troubleshooting

### "Cannot connect to X server"

PyBullet GUI requires a display:
```bash
# Use virtual display
xvfb-run python standalone_simulation.py

# Or use X11 forwarding
ssh -X user@host
```

### Drone flies erratically

Reduce control gains in `drone_controller.py`:
```python
Kp = 0.3
Kd = 0.2
```

### Camera image not appearing

Install Pillow:
```bash
pip install pillow
```