Update: The answer below is outdated. Texture Tools Exporter 2024.1.1 now allows you to force _SRGB or non-_SRGB formats! You can find the setting for this at the bottom of the settings pane, under “Export Transfer Function”. For more information, please see Color conversion exceptions using nvtt export - #5 by nbickford !
Hi lu_zero! I think what might be going on here is that the game might be expecting a DX10 DXGI format that ends in _SRGB, like DXGI_FORMAT_BC7_UNORM_SRGB (which Custom_Samurai_d_HI.dds uses) or DXGI_FORMAT_BC3_UNORM_SRGB, but nvtt_export is writing a file using the DXGI_FORMAT_BC3_UNORM DXGI format.
There’s two parts to this: the first is that nvtt_export doesn’t use the DXT10 DDS extension by default, and the second is specifying the _SRGB DXGI format.
To use the DXT10 DDS extension, set Format to BC3, then scroll to the bottom and check DDS: Use DXT10 Header:
What’s going on here is that DirectX 9-era DDS files specify their format using the DDS_PIXELFORMAT struct, which doesn’t have any information about whether the file should be read as linear or sRGB. The optional DXT10 header extension (from the mid-2000s) adds a DXGI format field which allows saying whether a file is BC3_UNORM or BC3_UNORM_SRGB – but some older DDS readers will crash if they see the DXT10 header, so nvtt_export doesn’t write it by default. My best guess is that the game might be loading the DX9 BC3 file as if it had the BC3_UNORM DXGI format, when it should load it with the BC3_UNORM_SRGB format.
The second part is that nvtt_export writes the BC3_UNORM enum without BC3_UNORM_SRGB by default (it might in the future though! I’ve written a bit more about this here). These contain the same data (the colors are sRGB in both files); the difference is that the GPU automatically performs sRGB-to-linear conversion on the fly for the latter.
Changing this is a bit trickier, and requires a hex editor at the moment (I often use HxD or ImHex; the design is that ideally the engine should do this format changing, but it looks like the engine doesn’t do that here). After writing the DDS file using nvtt_export.exe, load the DDS file into your hex editor. You should see something like this:
Click on the byte at offset 0x80 and change it from 4D (hexadecimal for 77, which is DXGI_FORMAT_BC3_UNORM) to 4E (hexadecimal for 78, which is DXGI_FORMAT_BC3_UNORM_SRGB):
Then save the file back out. If UNORM_SRGB vs. UNORM was the root cause, the texture should now load correctly!
Hope this helps, and let me know if this works!
