Problem rendering thin lines

[dennisqdw]

Ok, I have 12 thin parallel lines (strings on an instrument), and randomly small segments of the lines will not render. The missing segments will change from frame to frame in an animation, and they will also change in rerendering the same frame if I change the "render region division" sizes, which was one of the attempts to fix the problem. At first I thought that it was caused by a thin line being right on the edge of one of those divisions, but I changed the size so that all the lines were completely enclosed by a render block, but even within that small segments failed to render. I have also tried every anti-aliasing option with no difference. I have also tried making the strings fatter (within reason) and that did not solve the problem, although I imagine if I made them super fat it might.
So anyone have any ideas? or is this a bug. It's really irritating as I'm ready to do my final render and can't.

[dlparisi]

Which image sampler are you using - adaptive DMC or adapt. subdivision? I've had similar problems when using adaptive subdivsion.

[dennisqdw]

That was it! thanx so much for the fast reply. Adaptive DMC did the trick. I can move forward now. Does anyone know why adaptive subdivision causes this sort of problem?

[vlado]

With such thin lines you need to increase the Min. rate for the adaptive subdivision sampler; the default is -1, but it should really be 0 or even 1 in such cases.

Best regards,
Vlado