Different colors -- or different shapes, which is also very helpful. :)

I've done a lot of charsets with the brow body part, though now it's hit or miss. (If I think it adds something and the result is better quality, I will, if not, I don't.) Even being one of the people who has often included it, I managed to get reamed up one side and down the other when I didn't include browless versions of all the (40-odd) head textures. laugh So that brow thing... yeah.

With the many map versions option, you end up getting reamed twice as hard for file size and 'wasting all our hard drive space'. ;)

It's also something that can be done via blender node, but that requires more technical know-how to allow for the potential versatility it offers than many customers have (or are willing to fuss with if they want a click-and-render solution, which most seem to want).

-D
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It's all fun and games until someone loses an eye texture.