I'm having trouble rendering with Ambient Occlusion in Poser 6. I'm getting either leopard spots on the skin (see pic) or black smudges and lines all over the skin. I've tried adjusting the Max Distance and Bias of the light to various levels. In this case I'm also using face_off's Occlusion Master set to the default values. I scaled everything up to 1000% because I heard that can remove rendering artefacts... Nothing seems to work.

The spots above don't seem consistent with the AO ray bias being too small (although it's a little hard to tell from the above image). If you are using the AO node on a material that doesn't have displacement mapping, a ray bias of 0.4 inches should be fine, but in doubt - increasing to 0.7 should remove any blemishes. If you've got a rough displacement map, then a larger bias might be required. Try rendering the above with displacement mapping OFF in your render settings. Artifacts can also be caused by ray-traced shadows (and a very light ray bias on the light). If you turn OFF ray tracing in the render settings (which will turn off AO and Ray traced shadows), do you still get the artifacts?

I haven't applied any displacement maps. I did add a bump of 0.01 to the skin but it made no difference. I'm not sure of the difference between the Occlusion Master settings on Victoria's skin vs. the settings on the light itself (I've just got one IBL light with AO turned on, and those are the settings I've been fiddling with). Are the light settings meant to be the same as the Occlusion Master settings? Also, when I ran your OM wacro, then checked the Render Settings, raytracing wasn't turned on... it was still set at the default draft setting. Did I miss something? I just rendered with raytracing turned off and the spots are gone.

Okay, I've been doing some tests... I increased the ray bias in about 0.2 increments (in Occlusion Master) and had to take it to 2.5 on all Victoria's body parts before the leopard spots were completely gone. Something else a bit weird - the spots were never on her face, only on her body.

Mmmmmm, switch off all light based AO, and just try the OcclusionMaster wacro on default settings. Having both node based AO and light AO can sometimes cause a conflict. If you really want the light based AO too, then use a very large ray bias on the light (around the same value as the MaxDist you use on the OcclusionMaster). As for raytracing sometimes not being switched on, I've seen this happen before, and appears to be a bug in PoserPython. I've reported it to EF.