Adding weight to this is the Vulkan definition of PrimitiveID. That definition never mentions "rasterized", so its use of the term "processed" pretty...
All of that information can be found on the page I linked to. Well, not the Vulkan stuff, but Vulkan is implementable on anything that allows GL 4.x....
You cannot use an identifier before you declare it. With the exception of statements within a class member which refer to other members of that class...
You're not supposed to. That site is where you go when you want to learn how to use OpenGL. Once you understand how to use the API, you will have the...