For this recipe, we'll need two framebuffer objects, each associated with a texture. The first will be used for the original HDR render, and the second will be used for the two passes of the Gaussian blur operation. In the fragment shader, we'll access the original render via the variable HdrTex, and the two stages of the Gaussian blur will be accessed via BlurTex.

The uniform variable LumThresh is the minimum luminance value used in the second pass. Any pixels greater than that value will be extracted and blurred in the following passes.

Use a vertex shader that passes through the position and normal in eye coordinates.