Rendertime through the roof on some frames

[Laserschwert]

So, I don't know if this is a VRay problem or not, but I need some help either way:

I'm rendering a bunch of product shots a 3500 x 3500 pixels on our small render farm through Backburner with VRay 2.30.1 under 3ds max 2012 x64. The nodes are all identical, Core i7 @ 3.4 GHz, 8GB of RAM. The shots are pretty similar... they all show the same device, just from some different perspectives, the image content is basically the same and shouldn't change rendering time too much (the thing is realized just through a camera animation in the scene). Now, some frames render just as expected for about 4 hours, which is is a reasonable time for my settings and what's visible - some frames take maybe 5 or only 3.5 hours, depending on the image. But every now and then some frames suddenly take between 18 and 22 hours per frame! Sometimes the computer crashes completely, or Backburner just dies with a time out.

Now, those huge render times are probably not caused by too much stuff to be rendered (as most frames of the batch take around 4 hours). What else could cause this?

We've already disabled any power saving functionality that might throttle down the CPU... maybe temperature? But that should either turn of the PC or not... but not make rendertime longer, no?

I really have no idea what else to check... might Backburner be the problem? I'm using BB 2008.1, after the BB 2012 caused even more trouble with constant "maxadapter" errors.

[Morbid Angel]

wasn't there something like this with the licenses in vray that it disabled the acceleration if it couldn't get a license? Vlado...?

[Laserschwert]

And not getting a license would be a network problem, right?

The computers are all running Win7, and first my own workstation (also on Win7) was both license manager with the VRay dongle and the Backburner manager. The problem with that setup was a) my workstation would always have to be running and b) as soon as more than 10 render slaves got assigned to a job, some would fail (we think this was due to the connection limit per Windows 7 license). So we added a new server running Win 2008 Server to both work as VRay server (incl. dongle) and Backburner manager. Maybe a firewall problem? Rights management?

[vlado]

some frames take maybe 5 or only 3.5 hours, depending on the image. But every now and then some frames suddenly take between 18 and 22 hours per frame! Sometimes the computer crashes completely, or Backburner just dies with a time out.

Are they always the same frames? Can you get us the scene to vray@chaosgroup.com?

Best regards,
Vlado

[Laserschwert]

We haven't yet had the time to send the renderjob twice to check if it's always the same frames. Unfortunately I can't send you the scene because of an NDA, so I guess this is impossible to diagnose...

[vlado]

We can sign an NDA too, if required, but I can see where this might be more work to get it organized. So I guess next time then.

Best regards,
Vlado

[Olli96]

I have the same issue as Laserschwert, once in a while a frame will take ages. 13 Frames were done in 30-40 seconds, frame 15 suddenly took 5 minutes, frame 16 was back to normal. Its rendering right now so i cant check if there is a problem with that specific frame, but i will check it out tomorrow and report back.
I am not rendering through BB and dont use DR, just one machine that is also the license server and has the dongle pluged in. so i dont think its a network issue.

[vlado]

I can only repeat my reply above...

Best regards,
Vlado

[Laserschwert]

It looks like our slow render times might have been caused by a network problem which made writing the output files take HOURS (in fact the switch we've used for the render nodes was half fried, so it didn't manage to run full speed), so the complete task time for the frames was so incredibly high. We'll do some further renderings today, so we'll see if it's fixed now.

[windowlicker]

Interesting. I was gonna write about a similar experience I had some time ago, where a scene would go from 1h render times to 10h+ without any obvious explanation!
Turned out it was some textures for proxy trees which weren't avaliable to the render slaves. I guess they just kept requesting those textures, making the render take forever. Woud be nifty if Vray would give you some kind of warning if it encounters networking slowdowns/errors, but I'm not sure how that would work when rendering through Backburner.

[joconnell]

Best thing might be that once you've rendered a few frames and you've a rough idea what an average frame takes, to set a timeout in backburner so frames taking maybe 2 or 3 times the average get reset - http://area.autodesk.com/blogs/maxst...r_job_timeouts

[Morbid Angel]

Generally vray does print a missing texture warning, it can (I don't remember) be reflected in bb, but I am not positive about that.

[Olli96]

I am not sure if its a texture problem...
I had some time to test it again and it happens at a specific frame so i can reproduce the problem. The strange thing about it is that it only happens if i render without gi and with a material override (vray light mat + vray dirt) with vray toon. If i turn on the gi and use no toon or material override it renders fine.
I will upload the scene and send you (vlado) a link so you can test it.

EDIT: Tried it again and it seems to happen randomly, that specific frame just rendered fine but others took 2-3 times longer then normal.

[vlado]

I will upload the scene and send you (vlado) a link so you can test it.

Yes, please - it will be very very helpful.

Best regards,
Vlado

[tashko.zashev]

Hi Olli,
Does the issue persist when you change "Default geometry" option from "Dynamic" to Auto?
In our tests this solves it.