Function slabbed_vertices 

pub fn slabbed_vertices(
    array_id: Id<Array<(Vec3, Vec4)>>,
    vertex_index: u32,
    slab: &[u32],
    out_color: &mut Vec4,
    clip_pos: &mut Vec4,
)

This shader uses the instance_index as a slab [Id]. The instance_index is the [Id] of an [Array] of Vertexs. The vertex_index is the index of a Vertex within the [Array].