xGen Fur Flickering

[mimo8]

Hello everyone,

We are working on a little project using maya's new xgen hair and recently ran into a problem when it comes to rendering it in vray.

Up close the fur looks great, from a distance however the fur flickers in a "blotchy" kind of way. (I've linked a video at the end)

GI seems to be partly at fault, since rendering the fur without it gets rid of the flickering (it does make the fur look less appealing though).
We tried upping the GI Settings for the scene, as well as using 3x GI Subdivs Mult. for the fur using vRay Object Properties, but both seem to make no difference.

We would next try to test around different variations of settings and change up the GI methods (we used irradiance map / brute force) , but we are wondering if we may be doing something entirely wrong?
It would be very nice if someone could take a look at our settings and give us some insight.


Here are the Render Settings from our most recent render: http://pipe-studio.com/weird/Fur_Flicker_Settings.png

I have also uploaded a Test Project containing a Torus with similar fur/lighting using the same settings, which produces the same kind of flickering:
http://www.pipe-studio.com/weird/FurFlickerTests.zip

The Video can be found at: http://pipe-studio.com/weird/FurFlicker_Passes.mov or at http://vimeo.com/119110568 (password pipeflicker12345)


Thank you in Advance

Kind Regards
Martin

[ivaylo.ivanov]

Why not using the animation modes of the irradiance map? Or if the scene is static - multiframe incremental (or similar).

[vlado]

It may be possible to cheat the irradiance map into producing a stable result (i.e. if nothing moves but the camera, you can use a fly-through mode or precalculate the map for the entire sequence, or maybe the animation modes), but in general I wouldn't use the irradiance map for that at all. Brute force/brute force or brute force/light cache will work better for animations. With Embree for hair enabled, it won't be that slow either.

Best regards,
Vlado

[mimo8]

Thank you for your fast replies,

This shot is mostly static, in the beginning the camera zooms out very quickly for 10 frames, but since it is very fast and motion blurred, flickering won't be noticed. I don't need to render the first frames again, so long as the frames coming after them (the video I uploaded) look the same visually. (This is the WIP of the entire video: https://vimeo.com/118484845 pw: pipe9876)

Multiframe incremental seems to produce the same results (blotchy flickering), I am currently trying the Animation Mode.

Bruteforce/bruteforce gets rid of the flickering, but produces noise (which was expected). It seems I have to increase the GI Subdivisions to quite a high level (60+) to reduce it to a acceptable level, which doubles my render times (at least for my torus-fur-test scene). This is not necessarily a problem for this particular project as long as it works, it does seem quite heavy on the render times though.

I didn't know Embree existed until now. I've read in the vray documentation that using Embree reduces the render time of static geometry (while using more RAM) by checking "Use Embree" in the Render Settings / Settings Tab and setting "Default Geometry" to "Static". Doing this however has no difference in render times for me. Is there something else to consider when using Embree Raycaster? I have also read that Embree is designed for newer Intel CPUs, we are currently using i7 950@3066 in our farm, which are quite old.

Thank you again for your help!

Kind Regards,
Martin


EDIT:
We used brute/brute with 70 samples and got a good result and reasonable render times, Thanks again for your help