When doing a heat haze shader effect (doom 3 like) in the fragment shader part you need to get the fragment coordinate and convert it to [0,1] range. How exactly is this done? It's just a variable that gets multiplied by the fragment coord but I don't know what goes into that variable. Also after this screen coord has been converted to [0,1] range and it has been shifted by a deform magnitude it needs to be adjusted for non power of two coords. This is again another multiply but I'm not sure what value to use. I understand the whole process of doing this effect but I'm stuck on how to get the two values I mentioned above to get it to work correctly. Thanks!