Due to space constraints, the entire fragment shader code isn't shown here. The full code is available from the GitHub repository. The fragment shader is implemented with five methods, one for each pass. The first pass renders the scene normally to the HDR texture. During this pass, the active framebuffer object is the one associated with the texture corresponding to HdrTex, so the output is sent directly to that texture.
The second pass reads from HdrTex, and writes out only pixels that have a luminance above the threshold value LumThresh. The value is (0,0,0,0) for pixels that have a brightness (luma) value below LumThresh. The output goes to the second framebuffer, which contains a much smaller texture (one-eighth the size ...
