# submap.material

`ogre_media/materials/scripts/submap.material` defines the OGRE material `cartographer_ros/Submap`, the source material that every `OgreSlice` clones at construction time.

```ogre
material cartographer_ros/Submap
{
  technique
  {
    pass
    {
      vertex_program_ref cartographer_ros/glsl120/submap.vert {}

      fragment_program_ref cartographer_ros/glsl120/submap.frag
      {
        param_named u_submap int 0
        param_named u_alpha float 1.0
      }
    }
  }
}
```

The material has a single technique with a single pass that binds:

- The vertex program `cartographer_ros/glsl120/submap.vert` (declared in `glsl120.program`).
- The fragment program `cartographer_ros/glsl120/submap.frag`, with the default parameters `u_submap = 0` (texture unit 0) and `u_alpha = 1.0`.

`OgreSlice` clones this material per slice (naming it `SubmapMaterial-<trajectory>-<submap>-<slice>`) and then overrides `u_alpha` at render time via `SetAlpha()`. The texture bound to unit 0 is uploaded by `OgreSlice::Update()` from the submap texture pixels returned by the `SubmapQuery` service.