Most of the times AO with IBL can bring even the strongest PCs to their virtual knees, particularly if lots of transmaps are used in the scene. Rendering the scene twice might be the solution: 1. With AO on everything except the hair/other offending object (by turning the Visible in Raytracing option off in Properties) 2. With AO turned off in IBL Properties but Visible in Raytracing turned ON - this way the hair will cast shadows but will not kill the machine with AO calculating. and combining the two renders in postwork later. Hope this helps and sorry for finding this thread so late :( Michal 4blueyes