   Specular convolution for image based lighting
  Hi,I doing image based lighting in GLSL. I have HDR (float) and LDR (ubyte) cubemaps for display as the background and for the lighting as follows:1. A diffuse cubemap which is a 180deg convolution of the original and is referenced using the surface normal for the diffuse lighting term.2. A specular cubemap which is mipmapped with the top level being the original image and successive levels being phong convolutions for the material exponent values in the range 0 - 128 (as per OpenGL).My problem is with creating the different covolutions for the mipmap levels for 2 above. The top level version is used for display as the background and the successive levels are accessed within GLSL for less shiny materials.I tried using HDRShop's Diffuse/Specular Convolution but the exponent values seems very arbitrary with no upper limit, and I can't understand how this relates to OpenGL's 0 - 128 range (128 in HDRShop is still very blurred)?Also, using HDRShop means doing each level by hand and only on small versions of the image. Is there a better (or more automatic) way to do the phong convolutions, and maybe automatically create them in a mipmap?Or am I going about this in the wrong way altogether?Thanks,Chris.   