# Unitree Go1 Robot with Stairs

## Overview
This tutorial demonstrates setting up a 3D scene containing a Unitree Go1 quadruped robot positioned in front of a staircase, along with lighting and atmospheric effects.

## Scene Components

The visualization includes four main elements:

1. **Unitree Go1 Robot** - A quadrupedal robot model loaded via URDF format
2. **Stairway Mesh** - A textured 3D model of stairs
3. **Fog Effect** - Atmospheric fog that darkens distant portions of the scene
4. **Lighting** - An ambient light source plus two movable point lights

## Complete Code Example

```python
import math
import asyncio
from vuer import Vuer
from vuer.schemas import Scene, Urdf, Obj, AmbientLight, PointLight, Movable, Plane, Fog

app = Vuer()

@app.spawn(start=True)
async def main(session):
    # Setup scene with fog and lighting
    session.set @ Scene(
        # Add fog effect
        Fog(
            color="#000000",
            near=1,
            far=20,
        ),

        # Ground plane
        Plane(
            args=[100, 100],
            position=[0, -0.01, 0],
            rotation=[-1.57, 0, 0],
            key="ground",
        ),

        # Staircase mesh
        Obj(
            src="/static/stairs/stairs.obj",
            position=[2, 0, 0],
            rotation=[0, 0, 0],
            materialType="standard",
            material={
                "color": "#cccccc",
                "roughness": 0.8,
            },
            key="stairs",
        ),

        # Ambient lighting
        AmbientLight(intensity=1.0),

        # Movable point lights
        Movable(
            PointLight(
                intensity=3.0,
                position=[2, 3, 2],
                key="light-1",
            )
        ),
        Movable(
            PointLight(
                intensity=3.0,
                position=[-2, 3, -2],
                key="light-2",
            )
        ),
    )

    # Animation loop for the robot
    for i in range(10000):
        # Calculate joint angles using sinusoidal functions
        hip_angle = 0.3 * math.sin(i * 0.1)
        thigh_angle = 0.785 - 0.25 * math.sin(i * 0.1)
        calf_angle = -1.5 + 0.5 * math.sin(i * 0.1)

        # Update robot position and joints
        session.upsert @ Urdf(
            src="/static/go1/go1.urdf",
            position=[0, 0, 0.33],
            rotation=[0, 0, 0],
            jointValues={
                # Front Left
                "FL_hip_joint": hip_angle,
                "FL_thigh_joint": thigh_angle,
                "FL_calf_joint": calf_angle,

                # Front Right
                "FR_hip_joint": -hip_angle,
                "FR_thigh_joint": thigh_angle,
                "FR_calf_joint": calf_angle,

                # Rear Left
                "RL_hip_joint": -hip_angle,
                "RL_thigh_joint": thigh_angle,
                "RL_calf_joint": calf_angle,

                # Rear Right
                "RR_hip_joint": hip_angle,
                "RR_thigh_joint": thigh_angle,
                "RR_calf_joint": calf_angle,
            },
            key="go1-robot",
        )

        # Update at ~60 FPS
        await asyncio.sleep(0.016)

app.run()
```

## Key Features

### Fog Effect
Creates atmospheric depth:
```python
Fog(
    color="#000000",  # Black fog
    near=1,           # Fog starts at distance 1
    far=20,           # Full fog at distance 20
)
```

### Ground Plane
A large plane rotated to be horizontal:
```python
Plane(
    args=[100, 100],              # 100x100 units
    position=[0, -0.01, 0],       # Slightly below origin
    rotation=[-1.57, 0, 0],       # Rotated 90° (π/2)
)
```

### Staircase Mesh
3D model with material properties:
```python
Obj(
    src="/static/stairs/stairs.obj",
    materialType="standard",
    material={
        "color": "#cccccc",
        "roughness": 0.8,
    },
)
```

## Robot Animation

The application updates continuously at approximately 60 frames per second, calculating joint values like:

```python
thigh_angle = 0.785 - 0.25 * math.sin(i * 0.1)
```

This creates realistic walking motion across the stair scene.

## Leg Coordination

The Go1 has a specific gait pattern:
- Front Left and Rear Right move together (same hip angle)
- Front Right and Rear Left move together (opposite hip angle)

This creates a natural trotting gait.

## Assets Required

Make sure you have the following assets:
- `go1.urdf` - Robot description file
- `stairs.obj` - Staircase 3D model
- Associated mesh files for the Go1 robot

## Source

Documentation: https://docs.vuer.ai/en/latest/tutorials/robotics/urdf_go1_stairs.html