title: Coordinates in vertex/fragment shaders
body: <p>I would like to perform a per-pixel operation on every instance of a mesh. I found a variable called gl_FragCoord but it seems that it's coordinates are the SCREEN coordinates. I would like to have access to the LOCAL coordinates so that I could make changes that would affect every mesh independently. I would like to have coordinates where for example the (0.0, 0.0) coordinates are the top-left corner of the fragment and (1.0, 1.0) are the bottom-right ones. </p>