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Normal map averaging #53
Description
Activity
Can you explain the use-case for the feature a bit? The old
D3DXfunction had a number of features which are in the DirectXTex version by combiningCNMAP_CHANNEL_*flags. The code is already set up to use the first0xfmask of theCNMAP_FLAGSto select the height-computation mode, so it should b easy enough to add another case.Basically if someone had a previously lets say BC5 encoded image and wanted to decode and use it in Blender per say, it's easier on the user to plugin a normal map with a precalculated blue channel instead of adding the calculation into the material itself. So it would be useful when transcoding between various 2 channel compressions. It would also be useful to get this working on the GPU as well for the added performance.
So basically you want a way to take a
BC5_UNORMtexture and have it generate a RGB texture where the 'missing' 3rd channel is reconstructed.In a shader, this is done with:
float z = sqrt(1 - dot(xy, xy));That's probably an easy addition to the
texconvtool with a special flag.-navgis probably not the right switch since it's not really an average. Maybe-reconstructz?For
BC5_UNORMit would need to do an x2 debias and reconstruct. If the output is_UNORM, it would need to bias x2. This is already covered byTEX_FILTER_FLOAT_X2BIAS.Yes that was the idea.
Another way to achieve this would be to add special logic to
Decompressso that if the target format has a blue channel it reconstructs it. Of course, that's probably the same as just having it always do that and the B channel would be saved or not depending on the output format.Fixed in this commit. Keep in mind you still need to ensure the output has a blue channel (such as with
-f R8G8B8A8_UNORM.
Would you be interested a feature to calculate the blue channel of a normal map (Given R/G (X/Y))? It was included in the old NVidia tools and would make a great addition to the library, I'd be willing to write the code for this if you'd be willing to merge! Some flag like -navg or something...