Weird artifacts in network rendering

[windowlicker]

As you can see from the image, I get these weird splotches in my renders. The tests I did on my own machine looked fine, but when I ran it over Backburner, I got these weird artifacts.
Anyone knows what it could be?

I checked the Irrmap in Irrmapviewer, and it looks totally fine.

I set up the render as follows:

1. Prepass with Irrmap (Multiframe incremental) and Lightcache (Fly-through).
2. Render the animations with the pre-calculated maps.

I run Max Design 2010 SP1, Vray 1.50.SP3a

[jacksc02]

are you saving the pre calculated GI to a shared location that the render nodes can see?

[windowlicker]

Yeah. All files are on server, and I'm getting no I/O-errors what so ever.

Since I posted first, I have re-calculated the lightcache - first over a small segment of the animation (5 frames) which rendered alright - then over the whole thing (450 frames) which is getting the same artifacts.
I tried upping the LC subdivs to 3000, but that appearently had no effect.

This is really annoying. And the deadline is uncomfortably close.

[jacksc02]

what value as a "nth" frame are you using?
I would use "incremental add" rather than multiframe incremental as well

[windowlicker]

I've had some problems with the "incremental add" when moving "into" the model and around corners... But is there really any big difference between the two modes?

I think I'll just divide the render jobs per machine now... and leave it over the weekend. I think I'll have enough time to re-run the problem renders, and run a new Irrmap/LC on them.

Oh, and nth frame is at 1.

[devin]

I had the same problem last night, I was rendering out 4 cameras from the same model and one of them was showing the same kind of problems yours was. I thought it might be material based but it wasn't so I re-rendered the IR and the problem went away. The only thing that was different was this camera had one error on one of the nth frames, it said "[Vray] Could not save irradiance map". I'm guessing that when this happens the IR Map gets screwed up, is it because the hard drive the file is being written to is to slow and can't write all the data in time?

[add101]

what 'nth frame' interval did you use whe calculating irradiance map.
i've had similar issues when using low values - normally just shadow/noise though- not colours.
if thats the issue you could calculate and save irradiance map from that view and then join it to ir map that's already calculated.

[devin]

I calculated for every 5th frame on all the cameras, since it only showed up on the cameras that experienced an error it seems clear that's what's causing the problem. I talked with our IT department about it, we checked out the network setup and the server receiving the data was receiving it through several switches. We re-routed it so that the render boxes rendering the prepass would have direct access to the server, hopefully that will stop any future errors from happening.

[windowlicker]

I also suspect it might have to do with a slow/bad connection to the server storing the irrmaps/lightcaches. Unfortunately, I can't prove it at the moment.

In the end I let each machine render each shot on its own. It's not a very good solution, but I made the deadline, so I'm happy. I'll talk to my IT department aswell, and see if we can speed up our server.

Thanks for your help, all!

[devin]

It looks like my attempt to speed up the network connection had no effect and I'm still getting errors. I'm not sure if the server it's self is to slow or if it's the gigabit network connection, I'm skeptical that it's the network as the files involved aren't that big.