Flickering geometry

[chris_rw]

I have a tight turnaround on a video that requires some space battles, so I bought a model off of Turbosquid... which I try to avoid for exactly the reasons below!

The model looks great and in my test renders I was very happy with it. When rendering an animation though, the geometry flickers and changes. I suspect that whoever built the model packed in so much micro-details right on top of each other, I'm getting the flickering effect from geometry that is stacked too close together (a panel is only a fraction of an inch above the 'hull' that it sits on). Is there anything I can do to try to help this (aside from remodelling the entire thing myself)? The polygons aren't necessarly 100% on each other, but it's damn close.

Attached is a render. It's easiest to see the effect on the 'windows' of the ship, which are small planes hovering above the geometry. You can see in the two frames how the window pattern changes frame to frame.

[cheerioboy]

Are you able to split out the passes and isolate the flickering? My first thought is possibly adjusting Secondary rays bias to .001

[Morbid Angel]

Well I think the flickering is not related to how close the polygons are to each other. That is, unless they are exactly on top of each other i.e. they take the same space, then they might flicker. I think the problem you are seeing is low sampling. For very fine detail, like fine dots, fine lines etc you must increase the min samples. I am not sure what sample settings you have, but for example you would have to set in DMC sampler min sample to 3-8, and max samples to 24-32. Then also reduce the noise threshold a lot, like 0.005 for this fine detail.

For the overlapping geometry, if indeed you have it, then in the global options you have a parameter called offset ray bias (or just ray bias). Set it 0.01 and that should fix any overlap flickering.

[chris_rw]

Fantastic, I'll try these settings and see if it fixes the problems! Thanks!

[steveblake]

Seems like you have the solution, but if all else fails try isolating parts (ie one half of the overlapping geo) in the offending area and add a shell or push modifier on a tiny increment.