Why not just map it so that the walls/roof can be makde invisible? But perhaps that's what you meant? :o) It looks really nice as far as I can tell, but the picture is very dark... It LOOKS Like the steps are a bit rounded? Poser does that to models. You might want to split the vertices. IF they're rounded of course and you don't want them to be, I can't tell exactely ;o)

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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.