I wish more merchants would do something like that, because it adds great flexibility to a materials set - e.g. I like this character's base texture but I like that other character's freckle map.  Maybe it's some heinous sin to do freckles that way but it makes sense to me.  Logically I would think the Physicalc Realism Kits work this way (I don't own them and can't use them until there's a 64-bit python interpreter to run them with).

I take it you got it working pretty well?  Results look pretty nice imo.

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