title: Does calculating texture Coordinates in the vertex shader increase performance in GLSL?
body: <p>I recently read (for the first time) that passing an array with texture coordinates to the fragment shader for multiple lookups of a sampler is way quicker than calculating them in the fragment shader, because opengl can then prefetch these pixels. Is that true ? If so, what are the limitations ? Do I have to tell opengl that these coordinates will be used a texCoords ?</p>