Selecting Full Raytracing doesn't allow Carrara to "cheat" and save time while it's doing it's calculations. Using Full Raytracing forces Carrara to calculate the full path (4, 8 or whatever raytracing options you have set)of all rays instead of thinking, "these two light paths are similar so I'll only figure for one of them". Likewise, Interpolation for global illumination does something similar. Since doing the complete calculations for global illumination is very complex (takes time), interpolation accuracy simply tells Carrara how much "educated guessing" to do resutling in saved time. The default is 20% percent accuracy which is a bunch of guess work. That's why some renderings look so blocky - the guess was inaccurate. Eliminating or reducing the interpolation plus forcing Carrara to calculate all of the light rays gives a better result - but it will result in an increase in render time. Mark