Adding Render Elements explods rendertime

[felix_schwarz]

Hi,

i currently have an issue with a maya scene. Whenever i add just any (I tried them all) render Element my rendertimes increase drastically. Looking at the Vray Render logs i could see it starts shooting extremely high amounts of unshaded rays, which causes the rendertimes to go up.
i just dont understand what causes this. Unfortunetly I cant share the scene but maybe someone has experienced something similar before.

Without Render Elements
[09:49:54.269] Camera rays: 4089366 (80.40 per pixel)
[09:49:54.276] Shadow rays: 99691750 (1959.97 per pixel)
[09:49:54.276] GI rays: 37739853 (741.98 per pixel)
[09:49:54.276] Reflection rays: 7071367 (139.02 per pixel)
[09:49:54.276] Refraction rays: 1162185 (22.85 per pixel)
[09:49:54.276] Unshaded rays: 842131 (16.56 per pixel)

With Render Elements
[09:55:16.616] Camera rays: 4077137 (80.16 per pixel)
[09:55:16.624] Shadow rays: 99417046 (1954.57 per pixel)
[09:55:16.624] GI rays: 37449035 (736.26 per pixel)
[09:55:16.625] Reflection rays: 7091279 (139.42 per pixel)
[09:55:16.625] Refraction rays: 1163702 (22.88 per pixel)
[09:55:16.625] Unshaded rays: 9392203509 (184653.26 per pixel)


Maya 2022.3
V-Ray 5, update 2.2

[seandunderdale]

Are you adding multi matte elements with "consider anti aliasing" enabled? Ive had experience of that slowing a render down a lot. Do you have any references in the scene? Sometimes an asset can bring in sneaky render elements from the scenes they were created in, like an AO or something.

[felix_schwarz]

No, I tried it with a GI or Lighting pass only and it still has the same effect. It doesnt matter if its a denoiser, a cryptomatte, ao or any other element. whenever 1 or more elements are added the rendertimes go up

[seandunderdale]

what kind of differences in render times are we talking about?

[felix_schwarz]

From 8 min to 2,5h

[hermit.crab]

Could you send the scene via the contact form so we can take a look?

[felix_schwarz]

uploaded the file (ticket ID is #44775)
I also attached an even simpler scene in here.

some further tests we did:
We imported all references and deleted most of the geometry
We assigned one basic vraymtl to all the geometry and deleted all other shaders and textures.
We removed pretty much everything, there were a lot (hundreds) of namespaces deleted, no change.
We also made a scene cleanup which deleted 200000 empty groupIDs, still the same behaviour, as soon as we add for example a zDepth RE it takes forever...

No idea why this is happening or how the unshaded rays can be limited. Help is much appreciated.

Thanks for your help