If you need to build a texture atlas from an already created texture that is not match a grid, you need to use new_empty and add_texture to create it. However it is not straight forward to get the index to be used with TextureAtlasSprite. add_texture should be changed to return the index to the texture.
Currently you can do something like this:
```rs
let texture = asset_server.load::<Texture>::("texture.png");
let texture_atlas = TextureAtlas::new_empty(texture, Vec2::new(40.0, 40.0));
texture_atlas.add_texture(Rect {
min: Vec2::new(20.0, 20.0),
max: Vec2::new(40.0, 40.0),
});
let index = (texture_atlas.len() - 1) as u32;
let texture_atlas_sprite = TextureAtlasSprite {
index,
Default::default()
};
```
But this is more clear
```rs
let index = texture_atlas.add_texture(Rect {
min: Vec2::new(20.0, 20.0),
max: Vec2::new(40.0, 40.0),
});
```