# Blender Models in Gazebo

Import 3D models from Blender into the ARG simulation.

## Workflow

```
Blender (.blend) → Export COLLADA (.dae) → Gazebo Model → World
```

## Step 1: Create Model in Blender

1. Create your 3D model
2. Apply all transforms: `Ctrl+A` → All Transforms
3. Set origin to geometry center

## Step 2: Export from Blender

1. File → Export → COLLADA (.dae)
2. Settings:
   - Selection Only (if needed)
   - Include Armatures: OFF
   - Include Animations: OFF
   - Triangulate: ON
3. Save as `model.dae`

## Step 3: Create Gazebo Model

```
gazebo/models/my_model/
├── model.config
├── model.sdf
├── meshes/
│   └── model.dae
└── materials/
    └── textures/
        └── texture.png
```

### model.config

```xml
<?xml version="1.0"?>
<model>
  <name>My Model</name>
  <version>1.0</version>
  <sdf version="1.9">model.sdf</sdf>
  <description>Custom Blender model</description>
</model>
```

### model.sdf

```xml
<?xml version="1.0"?>
<sdf version="1.9">
  <model name="my_model">
    <static>true</static>
    <link name="link">
      <collision name="collision">
        <geometry>
          <mesh>
            <uri>meshes/model.dae</uri>
            <scale>1 1 1</scale>
          </mesh>
        </geometry>
      </collision>
      <visual name="visual">
        <geometry>
          <mesh>
            <uri>meshes/model.dae</uri>
            <scale>1 1 1</scale>
          </mesh>
        </geometry>
      </visual>
    </link>
  </model>
</sdf>
```

## Step 4: Add to World

```xml
<include>
  <uri>model://my_model</uri>
  <name>my_model_instance</name>
  <pose>5 3 0 0 0 0</pose>
</include>
```

## Step 5: Set Model Path

```bash
export GZ_SIM_RESOURCE_PATH=$PWD/gazebo/models:$GZ_SIM_RESOURCE_PATH
```

## Common Issues

### Model Not Found
```bash
export GZ_SIM_RESOURCE_PATH=/full/path/to/gazebo/models:$GZ_SIM_RESOURCE_PATH
```

### Scale Wrong
In Blender, check unit settings: Properties → Scene → Units

Adjust in SDF:
```xml
<scale>0.01 0.01 0.01</scale>
```

### Textures Not Showing
Put textures in `materials/textures/` and reference in DAE file.

Or add material in SDF:
```xml
<visual name="visual">
  <geometry>
    <mesh><uri>meshes/model.dae</uri></mesh>
  </geometry>
  <material>
    <diffuse>0.8 0.2 0.2 1</diffuse>
  </material>
</visual>
```

### Model Orientation Wrong
Blender uses Z-up, Gazebo uses Z-up. Should match.

If rotated, fix in Blender or use pose:
```xml
<pose>0 0 0 1.5708 0 0</pose>
```

## Simplified Collision

For complex meshes, use simple collision:

```xml
<collision name="collision">
  <geometry>
    <box><size>2 2 3</size></box>
  </geometry>
</collision>
<visual name="visual">
  <geometry>
    <mesh><uri>meshes/complex_model.dae</uri></mesh>
  </geometry>
</visual>
```

## Template

Copy the template:
```bash
cp -r gazebo/models/custom_object gazebo/models/my_model
```

Then:
1. Edit `model.config` with your name
2. Edit `model.sdf` with your model name
3. Put your `model.dae` in `meshes/`

## Test Model

```bash
gz sim -v4 gazebo/worlds/custom_landing.sdf
```