If I remember BB¨'s explanations right, it's not possible. Not without cheating at least. I once tried to make a stained glass window and not even BB could make it work L

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.