looking for some help to trouble shoot some artifacts I'm seeing.
#1 i can't get rid of these blocky shapes in the shadows and underlip of the surface. two materials, back surface is a simple white diffuse material and the other is a plastic material.
#2 strange artifact on a flat surface, using a diffuse material.
Render settings:
Samples 20
ray bounces 6
anti aliasing 3
shadow 2
global illumination 1
Try turning on sharp shadows. I've had both of those problems. I'm not sure if it helps with the first problem, but it fixes the second one for me.