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Video Codec techniques in bump mapping

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In all breeds of MPEG and many of the other major video codecs, YV12 color space is used. This means: 1) The chroma(color) and the lumi(brightness) components of each texel are split so that 3 channels remain, Y(lumi), U(chroma1), V(chroma2) 2) The chroma is sampled at quarter resolution, meaning for 4 texels, there are 1(channel)*4(texels)*8 lumi bits + 2(channels)*1(texels)*8 chroma bits = 48 bit, or 12 bit per texel(hence YV12) 3) The chroma is able to be further compressed(eg. more bpp reduction) in later stages as it still has a fairly insignificant role in what our eyes pick up If you are using bump mapping, you can multiply the lumi by the normal map(scaling to avoid overflow, of course) thus having 5 channels of data, 2 of which are low-res, rather than the regular 6. Normal method(uncompressed): X8R8G8B8 color + X8R8G8B8 normal = 64bpp Color detail: 100% Lumi detail: 100% My method(uncompressed): 1/4 * R8G8 color + X8R8G8B8 normal = 36bpp Color detail: ~25% (Hey, DVD quality is actually worse than this) Lumi detail: ~99% (scaling the normals to allow lumi range 0-3 drops qual by 1.2%) Normal method(compressed): DXT1/S3TC color + DXT3/S3TC normal = 12bpp Color detail: ~50% Lumi detail: ~50% My method(compressed): 1/4 * DXT1/S3TC color + DXT3/S3TC normal = 9bpp Color detail: ~12.5% Lumi detail: ~50% So its basically a cheap way to be able to increase texture sizes by 25%-43.25% whilst losing an acceptable amount of detail

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