Thanks in advance for any help…
Within a fragment program, what is the range of gl_FragCoord.x,gl_FragCoord.y, and gl_FragCoord.z?
Are they simply window coordinates or do they vary from 0 to 1?
The spec states:
The variable gl_FragCoord is available as a read-only variable from within fragment shaders and it holds the window relative coordinates x, y, z, and 1/w values for the fragment. This value is the result of the fixed functionality that interpolates primitives after vertex processing to generate fragments. The z component is the depth value that would be used for the fragment’s depth if a shader contained no writes to gl_FragDepth. This is useful for invariance if a shader conditionally computes gl_FragDepth but otherwise wants the fixed functionality fragment depth.