I would like to create glsl to add to the emission(?) of an Entity which was loaded from a GLTF model. Specifically I want to add a procedural sparkle as f(fragcoord, time).
I've seen the material/appearance/fabric tutorials, and looked at the schema, but its still not clear how to do this specifically, mostly due to the lack of complete sandcastle-style examples. The terminology and relation between Material, MaterialAppearance, and Appearance is confusing as well. And I'm not sure how to reference and append to an Entity's model.material.materials(?)