Random extremely slow Light Cache calculation

[Vizioen]

Friends and colleagues of mine experienced the same things with 3.6. Sometimes a reinstall of Vray actually solved the problem. Might be worth giving it a shot.

[olika]

thanks Vizioen for that tip!
unfortunately i installed the new next version from a few days back yesterday with no benefit to that problem

[king_max]

I've just installed Max 2019 and fresh installed the latest build of V-ray 4. The problem persists. It's impossible to work, so I've reverted back to 3.6. This issue should be addressed asap.

[emonimo]

I'm having the same problem here. Just installed Vray Next 2 days ago. Working with a quite simple scene with some forest objects and some proxys. When I hide the big trees proxys and forest objects (just the big trees ones) Light Cache runs perfectly (15 -20 seconds), but when I unhide them it takes very long time (7 minutes aprox). And I'm just rendering a test render at 1.500 pixels...
The scene wit Vray 3.6 works perfect.

Is there any solution to this anoying bug?

[BBB3]

Having exactly the same problem now. Everything's fine in the IPR but when I start the production render, the light cache kicks off and slowly wheezes through, never completing. Getting rid of all the Forest Pack objects fixes the problem. It's not one Forest pack causing the problem. Happens with any one of them and seems to be causing an issue with the light cache.

EDIT: Seems to be something with overlapping meshes. Reduce the density of the Forest object enough and the problem goes away. LC behaves normally again.
Something's seriously wrong here.

EDIT2: Actually, that's not it. The culprit for me happens to be "motion blur" enabled in the physical camera. Untick that and everything works normally again.

[emonimo]

I found that restarting 3dsmax the scene works fine. I mean, if I'm working on any other scene,save it, and open the scene with the proxys and Forest Objects, the Light Cache calculation is too slow or even doesn`t start. But if I restart 3dsmax and open the problematic scene, it works fine.
This is really disturbing.

[fixeighted]

I don't know if this'll help but I had a major slowdown with some forest stuff that I figured out eventually was due to it having the trees that were used on my usual network drive.
If I used those that were local it appeared to fix the issue, or even if I collapsed the reference trees to meshes it was instantly quicker. Very odd.
This was with Max 2019 and I never had an issue using 2016.
In fact I've found that 2019 is demonstrably slower in opening files, saving files and initiating renders (transforming/LC etc.) so am thinking it could be 2019 that is the problem somehow.

[emonimo]

I'm using 3dsmax 2016 and all my trees a in the local drive... so this is not the problem I'm facing. Thanks anyway for the tip.

[Margarita.Stoeva]

Hi, everyone!
The issues you describe are definitely not to be ignored.
They seem to be different and we'll need specific scenes so that we could reproduce them here and see how to fix them.

Having exactly the same problem now. Everything's fine in the IPR but when I start the production render, the light cache kicks off and slowly wheezes through, never completing.
...
The culprit for me happens to be "motion blur" enabled in the physical camera. Untick that and everything works normally again.

BBB3, could you please send a simplified scene that demonstrates this LC calculation slow down with motion blur to support@chaosgroup.com (include a link to this tread)? It will help us a lot!

I found that restarting 3dsmax the scene works fine. I mean, if I'm working on any other scene,save it, and open the scene with the proxys and Forest Objects, the Light Cache calculation is too slow or even doesn`t start. But if I restart 3dsmax and open the problematic scene, it works fine.
This is really disturbing.

emonimo, this seems really odd. I would really like to check if LC is cleared on render end or not. Maybe there's something there... Can you too please send a scene to support@chaosgroup.com (with link to this tread)? And include steps to reproduce this - what modification do you do to your scene, how many renders does it take, do you render single frames or animation, do you use V-Ray Next or V-Ray Next GPU renderer? We would definitely check what's going on once we manage to reproduce this.


fixeighted, loading network assets in 3ds Max 2016 vs 2019, may not be a V-Ray issue, but we should check it as well with a properly set scene. Please, feel free to send such scene if you notice this issue again.

I'll keep in touch with the support guys and we'll do our best to get to the bottom of these issues.

Best regards,
Margarita

[BBB3]

Hey Margarita, Thanks for the offer. I'll try to prep a scene but since I've found a workaround it's low-priority for me now. I have a few more urgent issues I've raised (and for which I've sent a scene) on the nightlies discussion group.

[Adrian Malcherek]

Hi!

I have similar issues with quite simple animation of office interiors.
I cleaned scene up, optimize it and now it has 2,5 mln poly, proxy objects, model from Revit.
When I start Light Cache calculations Vray shows times like 500 hours to finish for about 6-7 minutes and after this it is starting working normally (1-2 min for building LC).

Firstly I thought it was Vray Fur and VrayDisplacement-mod (generating additional geometry) but after deleting these objects problem still exists.
I calculated LC and IR to file and now having another issue - render times with light maps from the file is bigger then launching render with light calculations.
When I use only pre calculated LC and IR calculations during render I have about 2 min per frame.
In opposite pre calculated IR and LC calculations during render about 8 min per frame.
When I load IR and LC from file it sometimes 8 min (Max is stuck for 6 min while processor on 100%) for the same frame and even 40 minutes for other from the same camera.
Max 2020, VrayNext 3.1, 2xXeon E5, 44 cores total, 128 GB

Do you have idea where I should look for the issue?

[^Lele^]

I shall sing out of the choir (as per usual) and ask you all to have *all* your assets local on a quick drive.
What you describe (besides those with genuine bugs) is *precisely* what is expected to happen with load-on-demand of proxies, much magnified by -possibly- infrastructure (slow network, server, and so on.).
You may want to read this guide thread, as you may find it somewhat helpful in understanding what to expect from your renders (The section on Proxies alone would suffice.).

Also, do not precalculate a thing anymore, rather follow our guidelines on how to render GI with animation: we know it's somewhat slower per frame, but overall the experience and time to completion of the job will be *much* shorter in most cases (because of both workflow simplicity, and coordinated technologies bringing their fruits.).