Animated faked GI objects rendering black in some areas

[tooves]

Hi all,

I'm having a bit of a problem with animated objects rendering weirdly in my 3D scenes.

Basic setup:
3ds max 2016, VRay 3.6.04, Windows 10

Basic visualisation scene using Lightcache, Irradiance map for static objects
Animated people are in a separate XREF, excluded from GI in VRay properties, and lit with a VRay Dome Light to approximate bounce lighting (which includes them only).

Some of the animated people are rendering black as they move through the scene.
The black shapes on the people do not seem to be linked to geometry or buckets, and you can also see it is happening in the people's reflections as well as the people geometry.
The people pass in and out of these 'square black areas' almost like they are walking though a voxel cloud or something.
I have tried using a different light (VRay ambient light) to fake GI for the people but it has the same issue.

I have provided a link to some WIP clips which show the problem as it is a bit hard to describe in words.

Does anyone know what is causing this or how can I avoid it? Is there a better way to fake GI on animated objects?
I've been using this technique for years with no issue so am a bit stumped as to what is causing it now.

Thanks!

[Morbid Angel]

Hey, I would suspect its something to do with xref. But before that, how did you precalculate the lightcache and irradiance map? Did you hide the people entirely because it looks like some of the static objects are also experiencing artifacts. In theory, if you light the scene and bake gi for static objects, you cannot have it cast gi / etc on the animated ones. So in that case how did you render the people, what happened to the static objects when you rendered people pass?

[tooves]

Hi Dmitry,
Thanks for responding.
The people are in an xref with a VRayDomeLight which only includes them (to fake GI).

All of the people are set to ignore/not cast GI and are not visible to GI.
I have the people loaded into the file for the pre-calc, which should be fine as they are not visible to GI as this is the way I have done it for years. Happy to try something different though!

Lightcache calculation: Multiframe incremental
Irradiance Map calculation: Fly-through

Not sure what other info might be helpful.. ..maybe my methods need updating. What is everyone else doing to render/light animated people in these kind of scenes?

[Morbid Angel]

i would first isolate the people from the scene entirely. So, don't use multi-frame incremental or fly through. Instead set the gi mode to single frame and check "use camera path" for irmap and light cache and calculate those (save to file) then load those and render the frames without people. If that works and all is fine you can bring in people and see what happens. If the same issue happens, then you might have to import the xref and try again (if that fixes the issue) then its related to xref.