I have read the OpenGl documentation of texelFetch, which is:
gvec4 texelFetch(gsampler2D sampler, ivec2 P, int lod).
I know the first argument "sampler" is just a texture. But I am very confused about the second and third arguments.
According to the documentation, the second argument "P" is a texture coordinate. But it has the type ivec2, which means that it is a vector of integers. Shouldn't a texture coordinate be in the range [0, 1]?
And for the third argument "lod", in the documentation, it said "If present, specifies the level-of-detail within the texture from which the texel will be fetched." I have no idea how to set this argument...
Could anyone explain this and give a real example of how to use texelFetch?