Mike, primitives are easily defineable with mathematical functions. While a complex polymorphic mesh would need a polygon coordinates description (such as the one you can "admire" if you open an obj file in a text editor), primitives don't need more than a short formula to be "produced". To make a rough, imprecise but useful comparison with 2D, polygons coordinates formats such as obj are the "bitmap art" of 3D, while the functions are the "vector art" of 3D... lol! This is to say that I'm almost sure that Vue primitives don't exist anywhere, but are simply generated by Vue's engine form a mathematical function, whenever they are "called" by the user... Having that said, once created though, they should behave like all other meshes in the scene... but evidently they don't, according to the results of the cloud materials mapping... so this is what makes me wonder, if there's something more/different behind all this, that escapes my knowledge and comprehension...