Network Rendering Problem

[Devin Johnston]

When I send an animation job out to be rendered by the farm I will occasionally get some frames back that are different than all the others. Usually it's only one thing in the scene that is flickering and I can't figure out how to fix this other than exclude whichever machines are rendering out the different frames from the job. I've turned on "Force 2-Sided" within each material, I've tried flipping the Normals and that has no effect. When the job is sent out I include all the maps, but even if I don’t all of my maps are available over the network. Each machine is running the same operating system with the same service pack and there all the maps reside on one server and are controlled by one manager. Can anyone help me figure this out?

[Crazy Homeless Guy]

i assume you are using 3dmax. i had this problem. it only effected the surface styles where i was using a texture as a reflection map. ...and more interesting, it was only on the machines that i had actually used 3dmax on. if i just installed max on a machine for rendering, but never actually launched the app, everything was fine. which suxks, because typically you use max on your most powerful machine. i never actually figured out what was causing this.

 

note: i was using a standard material with vray when i had this problem. not sure if vray was causing it though.

[Devin Johnston]

My flickering occurs on surfaces with or without reflections, some times it's a ceiling and sometimes it's a baseboard or window. It's really random and it's driving me crazy!

[abicalho]

From the brief description, it seems to me you have coplanar faces.

 

Alexander

[Devin Johnston]

Coplanar faces are objects that over lap right?

[John Dollus]

Yes. 2 faces in the same plane on top of each other.

[Devin Johnston]

I've checked but that's not it, any other suggestions?

[Crazy Homeless Guy]

maybe post a clip, or part of your file so we can look at it.

[quizzy]

Well, I had the same where 2 PC's rendered one texture wrongly. I had to delete these frames and re-render them on other machines.. Ow, I had NO coplanar faces etc.... very clean modelling if I say so myself.. Propably a memory error of some kind.. I didn't find out what was causing it..

[Devin Johnston]

Here are two images from the animation; if you look in the upper right you will see that the ceiling inside the room is different colors. Everything else in the scene is the same except for that ceiling which flickers from bright to dark. The ceiling has no coplanar faces, forced 2 sided is turned on. This is a Max radiosity model using regathering, any ideas?

[quizzy]

Its propably a regathering error (bug) in max5 (?) I had the same error (bug) when rendering an animation with regathering, sometimes objects behind transparent objects didn't regather. Didn't matter if there was reflection on the objects..

[quizzy]

here you can find an example of the BUG:

 

http://www.3idee.nl/cgarchitect/error.avi

[Crazy Homeless Guy]

what happens if you assign a completely different surface style to it? apply the yellow wall surface style to it, and see if it still mis-renders that frame.

[Devin Johnston]

I'll give it a try and see what happens.

[abicalho]

Regathering processes each pixel of the image again. Since regathering is a stochastic process, each pixel will have a different color every time you render. That becomes more visible when you move the camera to a different frame.

 

The solution is the same used when you render an animated object with radiosity - you have to have enough quality that the difference is neglegible

 

So, in a nutshell, regather will flicker in animations except if you use a quality high enough that the change is not visible.

 

Alexander

[joske]

a while back at my office one pc had a VIZ4 installed and the others had max, it occured frequently that the pc with viz had different contrast, brightness etc...

so to rule out that it's not a network error, you could just re-assing the scene to just one pc, it will take a bit longer, but you could assign the other pcs with other parts/scene's (so no distributed scenes)

 

if the problem still occurs it probably has to do with the regathering issue mentioned above. than texture bake the lot, that's the best way to be sure, it'll take you a day or so to texture bake, but the frame will render in just one minute or so, so the whole movie'll render superfast

[Devin Johnston]

How do you texture bake with Max radiosity?

[joske]

not really sure about this i haven't used radiosity for a long time...

but doesn't texture baking come standard with max 5 max 6 even for radiosity?

 

it can be done with lighttracer for sure (we allways use that because Mray can't be texturebaked)

this is doable for even very big scene's, however the texture baking in max5 tends to be less stable than the one from max 6.

And the one from max 6 is very picky on wich kind of shadow u use

(some kinds don't even show up in baked textures) and does give some trouble in network texure baking (same no shadow bug)

 

but once the baking is setup fine the animation frames render superfast in full GI

[Devin Johnston]

I think Max 6 radiosity bakes the texture during it's radiosity processing, that's why this flickering thing bothers me. I think it's not so much the file but it's the computers that it renders on. Basically if the scene renders fine on one machine and the same frame renders differently on another then you have to come to the conclusion that it's the computer that’s screwing it up. I've just got to figure out what the differences are in the computes.

[abicalho]

It's not the computer. Radiosity and Regather are Stochastic. Every single time they're rendered it will be different. If you're rendering on 2 different machines, the differences will be even bigger.

 

You just do not have enough quality in your parameters to render an animation.

 

The best solution is simply to not use regather, and to process radiosity before you send the job to network render.

 

Alexander

[Crazy Homeless Guy]

I disagree. I think it is the computer. I think the flickering problem is the nature of a surface style rendering incorrectly, not the solution being poor. Could be wrong, but I have had a really similar problem that was the computer.

[Chad Warner]

I have had several occasions where a frame doesn't render correctly, for whatever reason. When re-submitted to a different computer (or sometimes even the same one), it renders fine. So I would agree with CHG.

 

-Chad

[abicalho]

If you're not using SSE and 2 computers render the same image differently, this is a bug. I'd really like to see an example of that.

 

Now he mentioned rendering with regather, and that will cause 2 different renders. Even on the same computer. I compared both files and I see a difference in the ceiling, but that's 2 different frames too. I'd like to see the same image processed in 2 different computers, or, if the same image shows this difference when rendered twice in the same computer.

 

Alexander

[Devin Johnston]

These are the setting I'm using with regather:

 

Initial Quality: 85%

Refine Iterations: 350

Filtering: 3

Radiosity Meshing: 2' to 6" depending on location

Rays per Sample: 100

Filter Radius: 5

no adaptive sampling

 

The two frames I posted were rendered on two different computers, but when I re-render the frame that was messed up on the computer that rendered the other frame correctly then the messed up images comes out correctly. That's why I think it's a computer problem because I can re-render all of the messed up frames on computers that I know render out correctly the first time and all the messed up frames come out fine. As far as quality goes what else can I do to increase that besides increase Initial Quality and the number of Refine Iterations, which I don't think would fix the problem anyway. After I finish this project I'm going to do some testing to find out which computers render different than all of the others, then maybe I can identify what the problem is.