"Long Distance" AO & "Thin Objects"

Hello all,

I’ve been using blender for about 6 months (and love it), but I’ve been pulling my hair out trying to track down an issue I’m having with ambient occlusion. Is seems that thin objects viewed over long distances get random noise when raytraced AO is turned on.

I’ve reduced the “effect” down to a box 10 x 10 x 0.02 blender units (right). No materials, complex lighting, etc. The thinner the object, the worse the effect (the left object is 0.05 BU’s thick).

Here’s a blend file, and a still frame (#165). If you render the animation (in the blend file), you can see what happens when the camera moves (lots of random triangle noise).

debug.blend (35.6 KB)

I have some wide shots in my animations, and this effect shows up on objects with “thin” meshes.

Is this something I have to live with (if I want to use raytraced AO), or is there something that can fix it?

Would the “sky dome” method work any differently?

I’ve tried changing random settings with raytraced AO, but can’t get rid of the effect. Approximate AO just doesn’t look as good (IMO).