When a DAI DDS normal map texture is opened via nVidia plugin for Photoshop
with default options, it looks wrong (very light).
In one of my previous journal entries I suggested gamma correction 0.42 to fix that.
That was acceptable, but not a precise solution.
After trying some other methods, I found which adjustments will result in exactly perfect histogram for all color channels:
1) when DDS texture is opened use "Convert Images to 32 bits" option in "NVIDIA DDS Read Properties" window
2) convert it to 16bits/Channel with default "Exposure and Gamma" method
3) apply Levels adjustment with gamma 0,45
These steps will result in perfect match with DDS texture opened via ATI Compressonator.
And don't forget to correct normal map coordinate system for use in your rendering application:
- Blender, 3DSMax, etc - swap Red and Green channels (as in GIF animation shown above)
- XNALara - invert Red channel then swap Red and Green channels