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Sunday, June 27, 2004 | Permalink

Source code
3Dc.7z (3.8 MB)
3Dc.zip (5.6 MB)

Pixel shader 2.0
Vertex shader 1.1

3Dc texture compression
This demo illustrates the use of the new 3Dc texture compression format, which is particularly suitable for normal map compression. It lets you compare quality between 3Dc and DXT5 normal maps, and it lets you compare the performance of using 3Dc and DXT compression over using uncompressed textures.

The performance increase of 3Dc and DXT is well worth the effort. Some benchmark numbers:

No compression: 125fps
3Dc: 146fps (+17%)
DXT: 136fps (+9%)
3Dc & DXT: 158fps (+26%)

That's with a fairly advanced shader, and overhead for the shadowmap which moves lot of workload where textures aren't used. Without shadows the difference is even larger:

No compression: 164fps
3Dc: 210fps (+28%)
DXT: 195fps (+19%)
3Dc & DXT: 239fps (+46%)

Quality-wise the DXT5 is often usable, but in some situations it just won't cut it. 3Dc on the other hand gives very good quality for all normal maps I've tried.

The demo also illustrates how to implement detail normal mapping. One normal map adds the large features, and on top of that another normal map is added that's sampled at a much higher frequency that adds the small details. Like with standard detail mapping for base textures this means you don't need to use very large textures to get a detailed image. A generic small or medium size detail normal map can be used together with a medium size normal map to get a final image that's easily comparable to a 4x4 times larger normal map.

It will run with 3Dc on by default on Radeon X800 cards. On Radeon 9500 and up, and on GeForce 5200 and up, it will run but with DXT5 as the only normal map compression option.