Full and Amient Occlusion are actually very different.

"Full" is more real - it actually creates the effect by tracing the light rays from object to object. It takes longer to render because of all the calculations, although.

Ambient Occlusion is best described as a "good guess" and takes less time to render. However, it is less realistic because it simply reduces the quantity of light at the locations where objects intersect or touch each other.

Now, to answer your question, use the one that best suites your desired image results. For example, if you have a red ball sitting on a white floor, "Full" will reflect some red from the ball onto the white floor where they come close to each other. Ambient Occlusion will only reduce the quantity of light making it darker but not reflecting the color. If you have similar colored objects or a lot of texture or bumps, AO can be a good choice because texture and bumps can obscure reflected color. Additionally it takes longer to calculate bumpy textures because bumps redirect the rays of light which requires more calculation time from the computer.

Mark

Message edited on: 03/06/2006 06:06