"Why does light sometimes leak through a sealed corner?" Shadow bias. Since computers do not have infinite precision but are rounding their 32 bit float numbers, programs add a slight bias to the shadow map's depth information in order to avoid self-shadowing. When the bias is too high, it can happen that shadows do not start at the floor where they should. Poser 4 does not give you direct access to the shadow bias value, but Poser 5 does, and you can recude such leaking by lowering the shadow bias. In Poser 4, you could have luck by adjusting the shadow lite cams, or maybe there's a hidden parameter for the shadow bias. Stefan