View Full Version : Mental ray batch render character rig/animation problem

08 August 2007, 02:11 PM

I have a really annoying problem with a render of a character animation I have. I have a skinned character with the usual controls including pole vector constraints for elbows.

My problem is that it looks ok in the viewport but when I run my render script the rendered animation is somewhat different. The problem seems to lie around the elbow, where it seems not to be constrained by the pole vector. I think. Anyway the elbows just follow the arm ik in whatever way they want.

Anyone experienced anything similar?



08 August 2007, 07:07 PM
yeah i had this problem witha an animated character where in the viewport looked right but in MR it was different, it happened in a fiew frames, so what i did in these frames was deleting the history of the mesh so it's frrezed in the right position and rendered the image.

i didn't have that problem in the maya software so i guess it's another consequence of a pathetic implementation of MR in Maya.

another way to fix the problem is to bake your animation into keyframes.


08 August 2007, 08:37 PM
Its a real pain in the arse, I have a render script ready to do 136 sequences, and now I cant trust it to render right.....

When you say bake the keyframes, do you mean bake the keys of animation curves, or do you mean bake the geometry into a cache? I tried this once and it seemed to fix it then, but trying it now with a more complex rig it doesnt like it very much....

Might look into baking the curves out....

Cheers for the tip.

08 August 2007, 09:14 PM
Turn off "Optimize animation detection" in the MR render globals.

08 August 2007, 10:19 PM
Thanks but I tried that already and it didnt seem to work. I did it in the maya file anyway. I dont know if you have to add that to the render script to get it to work in scripted batch renders....

Tried geometry caching but that gives me some strange results in the rest of the rig. Tried baking all the control curves out, I have had a few problems with mental ray in batch renders...

Any other suggestions? Dont know if I can bake out the joit rotations with an IK setup...

This is so annoying its the only thing left in the way of me finishing, I am ready to hit go.

08 August 2007, 11:57 PM
if baking the animation on your mesh doesn't work, try then the freezing method

08 August 2007, 01:16 PM
I understand the method, but my problem is that I have 4000 frames of animation! So even with the best will in the world I cant really do it. Also dont know if you get motion blur with that.

It renders ok through maya interface batch render I think...
Dont know why it doesnt with the scripted render. Its realy annoying as I have 4 cameras I want to render too, a ridiculous amount of extra work. Unless someone can help....

08 August 2007, 01:37 PM
Im not sure if this will help you, but I have noticed that sometimes these mentalray/animation related problems are solved if you render 1 frame at a time rather than batching a complete sequence of frames. I'm using a render farm so thats how it does it anyway, but you could do it with a command-line script also.

-- good luck, and sorry if this idea doesn't help.
-- David

08 August 2007, 02:17 PM
Ok interesting idea...Do you mean adding a line to the render script for every frame of the animation? I have 4000 frames so would that not take quite a long time as it has to load the scene for every frame it renders rather than for the whole sequence? Also would have a huge render script 4000 lines long. And theres different scenes in the same file, its not linear.

Anyway interesting idea. I will look into it. Deadline is very iminent...



08 August 2007, 11:31 AM
Well yes and no. :)
4000 lines would take a while to type! Before getting smedge to do my renders I used cygwin (on windows xp) to give me a unix shell to launch my renders. I wrote some shell-scripts that would loop through to render each frame. In this way I could launch a render by typing something like "ren 1 400 myScene.mb" and the shell script would set of each frame render one at a time, one after the other.

Yes, there is an inefficiency in that you have the overhead of loading the scene for each frame. If the render takes 30 secs per frame, but the scene takes 2 mins to load then this is bad, but if the render takes 30mins per frame, then that 2 min load time is not such an issue.

Might I suggest that you just try it for a few frames that you know were failing before. If this frame-by-frame method fixes the problem, then maybe I or someone else could help you out with some shell scripting to get the rest of the job done. Find out if its going to work first though.

-- David

08 August 2007, 12:41 PM
Cheers for that.

A render farm is what I would love to have access too. Feling really restricted by my machines.

I found a script over on highend3d that lets you render specific frames of the scene from within maya. So have adapted that and now can run my renders in chunks from the scene file to wherever I want. It previews the renders as they are going too which is useful for checking purposes, and means you only need to load the scene once. Which was a consideration as mine took about 2 mins to load.

Think this is the best solution for now, until I can get my hands on a render farm proper rendering software.

Thanks for all your help guys.


08 August 2007, 12:47 PM
p.s. To djx. Out of interest whats the 3d scene like in australia/melbourne? Is there much competition for jobs? Is it freelance mostly? Do studios take people from abroad?

Just wondering really, as I am looking to go and work abroad for a while in a year or so.

Also a broader question is that I am looking to get more into the TD arena, as my background is in software development and I have recently trained at escape studios in London, so just startin gto get into 3D properly. Do you have any tips on getting into TD stuff? Any tips for good things to show on reels?

Any advice appreciated. And thanks again for your help.


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