Non BC5 Normal Map has orientation issue.
Hi there , Apparently normal map NOT compressed with BC5 seems to have some world orientation issue ( not sure what's the correct term for it ) .
Right now my intention is to pack an alpha map into normal map to use as heightmap. For this I am using BC7.
Based on this answer , it seems to state that BC7 is a wise choice for normal map with alpha. https://answers.unrealengine.com/questions/9136/request-normal-map-compression-with-alpha-channel.html
However, when using BC7 , the material editor now refuses to use it as Normal sampler type and forced it to be Linear Color. This could potentially be the root problem,but I'm not sure.
However, right now when using BC7 Linear Color sampler as normal map , it works normally until you rotate objects. This is seriously bad because the object's lighting randomly go wonky at certain rotation.
asked May 26 '16 at 05:23 PM in Bug Reports
Your texture isn't being sampled correctly. The "Normal" sampler type outputs values from the texture in a -1...1 range, whereas the Color types output them in a 0...1 range. If you simply take the output of your Linear Color-sampled normal map texture and multiply it with 2, then subtract 1, you should get the correct values to use!
answered Jun 03 '16 at 03:48 AM
Hey Frozen, after the normal map texture, you might want to try a " Normalize" or " SafeNormalize" node.
That said, adding an alpha channel to a texture doubles the filesize, so it might be wiser to put three mask/height/grayscale textures in a seperate texture and only use the needed channel.
answered May 26 '16 at 05:49 PM
BC7 is not intended for support for Normal Map compression. BC5 is meant to be used for Normal maps because it's intended for compression of two-channel floating point data. BC7, on the other hand, is used for compression of 3 or 4 channel data which doesn't fit well with Normal maps.
This page should be able to help you understand some of the processes behind BCn compression methods: http://www.reedbeta.com/blog/2012/02/12/understanding-bcn-texture-compression-formats/
I hope this helps.
answered May 31 '16 at 05:15 PM
Tim Hobson ♦♦ STAFF
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