Nick Darnell a7a6176be2
Gamma Correction - Changing the way all FColors are converted into FLinearColor by default. Previously all sRGB textures coming into the engine along with all other usage of FColor -> FLinearColor used a lookup table that assumed the final gamma correction would simply be pow(color, 1/DisplayGamma). However, that's not the case, we use the IEC 61966-2-1 standard on most platforms for both the scene renderer, as well as for gamma correction in Slate. In Slate you should now see an image matching Photoshop instead of being slightly darker in the lower ranges. However, because we don't want to invalidate all existing textures that users have authored, all existing UTextures have a UseLegacyGamma flag set to true, all new textures will be set to false. The flag is part of the DDC key calculation, but steps were taken so that when legacy is true, keys match existing keys to prevent universally invalidating all games DDCs just to make this change. ...
To summarize,
Old Pipeline: sRGB-Pow(2.2) -> Linear -> sRGB-IEC 61966
New Pipeline: sRGB-IEC 61966 -> Linear -> sRGB-IEC 61966
#codereview gil.gribb, nick.penwarden, martin.mittring
[CL 2571070 by Nick Darnell in Main branch]
a7a6176be2