What I need is apparently very simple, a lookup table in a fragment shader. It seems that the natural way would be an array
float lut, but in some implementations of OpenGL ES I am getting an error
"profile requires index expression to be compile-time constant".
Next approach would be a 1D texture filled with the values, but again OpenGL ES doesn't like that :)
What would be the simplest way to have a lookup table of 256 float elements in the fragment shader? (I guess it will be a 2d texture but it looks like it is some overhead and I am not sure if it's possible to handle two textures on a shader)
P.S. I am a very beginner in OpenGL but what I need is simple handling of images in textures.