Ugly artifacts in Cycles rendering of Multires sculpt

Support Modeling
1

Sculpting the cliff faces of my latest model, I found that what I sculpt is not what I get:

CliffSculptArtifacts1024.jpg1024×609 192 KB

Larger image: http://img841.imageshack.us/img841/7233/cliffsculptartifacts.jpg

Circled in red, and at the red arrows, are deep creases and puckers that do not show at all in the UI, even at a preview level matching the Multires sculpt level (6). I’ve tried Smoothing these out (as can be seen in the UI window) to no avail. I don’t have a Subsurf modifier in effect since the Multires is at such a high level. Any suggestions about how to rid my sculpt of these glitches?

EDIT: It’s definitely an issue with Cycles.

CliffSculpt-BI-NoArtifacts.jpg708×791 101 KB

This rendering is using the BI engine with the same light source, a mesh light set here for Emit =1.0 and Indirect Lighting enabled. The sculpt looks eactly like the UI version.

Why is Cycles trashing my sculpt?

2

Arrrgh! Talk about annoying (but in a good way, kind of). I just reopened the file and the artifacts are gone, even in Cycles. I have no idea what might have caused them, but the file seems intact, no corruption evident. Guess it’s one for the Blender Mysteries anthology…

3

Turns out this isn’t a “solved” issue after all – the problem has returned, but this time I have little better handle on it. My sculpt is set for Multires level 6 for Preview, Sculpt & Render. But the UI-Rendered preview and the Cycles-rendered image only uses up to Multires level 4 – if I set Multires to Preview level 4, then the renderings match what I see in the UI/Solid view. If I can figure out why, I post back.