# PyBullet Simulation

Running the GPS-denied drone simulation with PyBullet.

## Windows (Standalone Mode)

No ROS 2 required! Run the all-in-one simulation:

```powershell
. .\activate.ps1
python standalone_simulation.py
```

### Options

```powershell
# Stationary landing pad
python standalone_simulation.py

# Moving rover patterns
python standalone_simulation.py --pattern circular --speed 0.3
python standalone_simulation.py --pattern linear --speed 0.5
python standalone_simulation.py --pattern square --speed 0.4

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)
```

The simulation includes a built-in landing controller. Watch the drone automatically land on the rover!

---

## Linux (Full ROS 2 Mode)

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

**Terminal 2 - ROS Bridge:**
```bash
source activate.sh
python ros_bridge.py
```

**Terminal 3 - Controllers:**
```bash
source activate.sh
python controllers.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
```

**Machine 2 (headless):**
```bash
source activate.sh
python ros_bridge.py --host <MACHINE_1_IP>
python controllers.py
```

---

## Simulation Parameters

| Parameter | Value |
|-----------|-------|
| Physics Rate | 240 Hz |
| Telemetry Rate | 24 Hz |
| Drone Mass | 1.0 kg |
| Gravity | -9.81 m/s² |

## 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 |

## Camera System

| Property | Value |
|----------|-------|
| Resolution | 320 x 240 |
| FOV | 60 degrees |
| Format | Base64 encoded JPEG |
| Direction | Downward-facing |

## World Setup

| Object | Position | Description |
|--------|----------|-------------|
| Ground | z = 0 | Infinite plane |
| Rover | (0, 0, 0.15) | 1m × 1m landing pad |
| Drone | (0, 0, 5) | Starting position |

## Building Executable

Create standalone executable:

```bash
source activate.sh
python build_exe.py
```

## Troubleshooting

### "Cannot connect to X server"

PyBullet requires a display:
- Run on machine with monitor
- Use X11 forwarding: `ssh -X user@host`
- Virtual display: `xvfb-run python simulation_host.py`

### Drone flies erratically

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

### Camera image not appearing

Ensure PIL/Pillow is installed:
```bash
pip install pillow
```