Render time issue when using Backburner

[REDVERTEX]

Hi everyone.

I wanted to ask if someone had experienced similar problem and if you have some advice.

We are having the following problem at the studio:
The render times of tasks, when using backburner, increase
dramatically, compared to local rendering. About 5-6 times higher.

This occurs on almost every render now. We have made an experiment
recently with one render. A colleague has rendered the image on his
computer for about 30 minutes. Then we submitted the image to Backburner
to be rendered on specific machine from the render farm, which is with
significantly better hardware, and the rendering took about 3-4 hours!
We then opened the same scene and rendered the same image on this faster
machine, but through 3dsMAX insted of Backburner and the render time
was normal - ~20 minutes.

We have observed this problem since we switched software versions, though some
colleagues say that they had even before the software upgrade.

We are now using 3dsMax Design 2014, V-ray 3.07 and Backburner 2014.0.3

Has anyone experienced such a problem? Any ideas?


Regards,
Alexander Alexandrov

[svetlozar.draganov]

Have you monitored the CPU utilization during the BB rendering? Are all of them 100% utilized or not?
Would it be possible to run another test with a completely new scene with a few basic primitives and a light?
Just set the Image Sampler to Fixed with 50 or 100 subdivisions in order to slow down the rendering and perform the same test.
Let us know the results afterwards.

[REDVERTEX]

Hi. thanks for a quick reply.

Yes, we have checked the CPU and it is at 100%

Will do the test with basic primitives and let you know.

Regards,
Alexander

[tricky]

So if you send the job via backburner to the same specific workstation that can render it locally in 30minutes, it takes 3-4hours?

[REDVERTEX]

Hi. Yes, this is exactly the issue.

[leo.surrealismo]

where do you have installed backburner manager? is it in the same machine that is rendering?

[REDVERTEX]

No, we have a render farm and the managaer is installed sepparately on a server and the server is not involved in any rendering.
Also, the render nodes do not have any unnecessary software on them.

[REDVERTEX]

Ok. I have made a quick test with a basic scene. Just some studio setup and rendered with
fixed sampler (way lower than you suggested, because render times were unbelievable)
I did not wait for the whole renders but I've waited enough for the estimate to be correct.
On my local machine the estimate was 2 hours and on a render node - 1h20m
which is about right, since the node is faster.
So on simple scenes there is no problem.

[svetlozar.draganov]

That is useful information, now we know that something in the scene causes this slowdown.
The next step would be to use one of your scenes which renders slow and remove all the 3rd partly plugins assets from it.
Any textures, geometries, caches or anything else created from external plugin should be removed. One way to ensure that the scene doesn't contain such data is to open it in 3DSMax which doesn't have any plugins installed, if something is left Max will inform you.

As addition to the above please remove any Xref scenes/objects as well and run another test render with and without BB.

[REDVERTEX]

Ok we will try that.

But just to mention another thing that we have discovered.
There had been issues when use presaved irradiance map.
We use the animation (prepass) and animation (rendering) modes
and on some occasions when we load the presaved IRR files and
start a render the renders have insane render times.
But the same scene when rendered with a brand new Irradiance
renders normally. In these cases we just start rendering again the whole
rradiance prepass and the second time it renders normally.
Don't know if this is related.

[Neilg]

the IRmap prepass/rendering is incredibly slow. it loads 5 frames worth of ir maps and blends them which takes forever.
Do all these tests with single frames because if you only see slowdown when loading in animation mode that's porbably just normal. it's not very good and animations with moving objects are better done with bf/lc

[svetlozar.draganov]

In terms of IM(rendering mode) - does the issue persist only with BB or the same slowdown appears even with V-Ray DR?
If there is an issue with IM caches it should appear even with V-Ray DR I guess.

Would it be possible to send us a vray-log file from one of the slaves after the frame is completed?

[REDVERTEX]

Hi again all,

We've done some testing here but couldn't find a solid solution for this.
We've removed all 3rd party plugings, motion blur. We don't have SSS materials or other fancy elements.

In the last scene we were rendering it happened again - rendering with animation prepass/light cache and then > animation rendering without engine for the secondary rays.
The scenes takes less than 10gb of ram on a computer with 32gb. It is with 'static' memory limit and the CPU is 100% busy.

Rendering locally takes 10-15 mins per frame, when submited with anim.renderin. option - on the same computer it takes 5 hours.

On the second try - GI precalculated with camera path both for irrandiance and LC, and then loaded 'from file' - renders for less than 10 mins.
The current scene contains some plugins, so the problem is not from them.

If anyone has any clues we'll be thankful. We are out of ideas...

P.s. - in the end if this problem presist we'll render the scene with 2 passes, irr-lc and brute force light cache; There are no errors in the vray log, only warnings of scene being too far from the origin.
On the next ocation we can copy the vray log.

[Morne]

I don't have a solution, but I do have something to share that may be related. I've noticed that with backburner and animation with BF and LC, randomly 1 or 2 slaves will render double as long as the others for no apparent reason, even though it's the same spec machines. Even the drives were cloned, just the name and IPs were changed and plugins installed afterwards. This isn't the same slaves all the time and seem very random. The workstation the job was submitted from on the other hand always renders with correct times.

Not sure if it's bacburner, windows, or V-Ray