To close the thread I'll post one last render; framed geometry with box primitives in black, IDL and point light downlights. Still some tweaking to do, but this is far and away the best result I have had from this geometry using IDL (I had tried box primitive masks on this before but not a complete mask and in white). Now a whole group of geometry that I felt was useless for IDL is in the useable with effort category. Thanks again!