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normal map texture compression

Started by xdotdt Jan 25, 2008 at 10:11 PM 0 replies 650+ views

Original Post

Jan 25, 2008 at 10:11 PM

With DXT format I have many artifacts of normal map texture. I've heard that in doom3, alpha channel and red channel were exchanged to reduce artifacts which is produced when an uncompressed normal texture is converted to DXT format. 3Dc format is also an alternative but it is not supported in nvidia video card. There are some alternatives like above and others, how do you think what the best alternative is for normap map texture compression instead of DXT in DirectX?

ViLiO

105

ViLiO

Jan 26, 2008 at 7:59 AM

A pretty common solution for tangent space normal maps is to compress with dxt5 using only the Alpha and Green channels for the X and Y respectively, then recreate the Z part of the normal in your shader (1.f - (Normal.x * Normal.x) - (Normal.y * Normal.y))

ATI Paper: Normal Map Compression

ATI Tool: Compressonator

Also, have a look at this entry on Christer's blog, for a nice little trick to handle dxt1 and dxt5 compressed normal maps with minimal effort.

Regards,
ViLiO

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