Remember that shadowmaps are calculated from the WHOLE scene. So if you have some huge prop, you will need a much bigger shadow map too. That could explain why the shadows dissapear when you add a character...

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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.