Anyway, it's apparently happening in one of the renderers at least, which is just a bug... if the software is going to render rear-facing polygons, it needs to flip the normal before computing the lighting. I can't think of any work-around off-hand, other than exporting the dress, flipping all the faces, possible scaling it slightly, re-importing it to use as the back/inside of the dress... ie. big pain in the ass.

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