Corrupted elements

[justini]

Still experiencing corrupted Reflection and LightSelect elements in Vray Next update 2.1. They are coming out blown out, noisy, and with weird circular artifacts over the entire image. Scene is quite heavy, with multiple large xrefs, but I wasn't having this issue with older versions late last year.

The attached images are crops from a 360 cube render. They show:

RGB element
Dome VrayLightSelect
Interior Lights VrayLightSelect
Sun VrayLightSelect
VrayReflection

The VrayLighting element is fine.

[tashko.zashev]

Hi,

The quality of the elements depends on their contribution to the beauty pass, so some of them can come out noisy for sure. Regarding the unexpected brightness of the Light selects, do you use any color corrections in the VFB ? Can you send us this file to try it here - our email is support@chaosgroup.com ? I believe that we don't need the entire project, just a stripped down version where we can see what is happening. having the file will help to find what are those circular lines over the grass area for an example, which I assume are the circular artifacts you are referring to ?

By the way, have you tried to render from a regular camera ? Does it change anything ?

[justini]

It seems that it had something to do with the chosen sampling type. I changed it from bucket to progressive and the elements rendered clean. So then I changed it back to Bucket sampler and it seems to have fixed it.

[justini]

Latest update: The render elements are fine when doing a small region render, but when the region gets bigger than a certain (seemingly artibrary) size, the elements then become corrupt again.

[tashko.zashev]

It's difficult for me to say what might be the reason for this result without the scene.
Can you send it to to our support mail? You can remove part of the scene elements to a stage where the issue still occurs.

[justini]

I've narrowed it down to one of the large xrefs. When it is on, the elements are bad. I've tried merging the xref and the problem still persists so perhaps its something within the xref that is causing it. I will continue to investigate and let you know.

[tashko.zashev]

Difficult issue to troubleshoot. You can send me the file to continue debugging it here when you are ready.
A few tips that may help, try to use the Light lister to eliminate some of the light sources, Enable Override material for a quick test in small region render. Switch of the Maps from the Global switches..

[justini]

Thanks. I'll try those, but I won't use the region render, because as I said earlier, it renders fine using just a small region render.

[justini]

Latest update. Turning light cache subdivs setting down to 500 fixes it. Turning it back to 2500 breaks it again. Still trying to identify if there is a culprit mesh or vrayproxy.

[tashko.zashev]

Switching Brute force / brute force for both primary and secondary does it work ?

[justini]

Yes, Switching to BF/BF fixes it. The problem only occurs when using LC.

I've identified the offending object as a VrayProxy, which was using a Autodesk Generic Material. Converting to Vray Material fixes the issue.

For your information to help bug hunting, this issue only occurred when the following conditions were present:

1) There is enough geometry in the scene (eg. as xrefs are disabled the problem begins to disappear)
2) There is enough instances of the VrayProxy
3) Resolution is high enough (no problem with small renders and region renders)
4) Sufficiently high Light cache subdivs

The exact threshold of these variables where the problem occurs is unknown.
As you begin to hide the VrayProxy instances or the Xref Scenes one by one the problem gradually disappears. (ie. density of bright artifacts in render elements reduces)

[tashko.zashev]

Thanks a lot for sharing the debug results! My advice is to convert all scene material to V-Ray ones since the unsupported materials are inefficient and can lead to artifacts in the final result. You can do this in two steps :
*) 3DS Max native Scene converter to make all Generic and other materials to Standard Mtls.
*) then using V-Ray scene converter to transform everything into a V-RayMTL.