Maya Bullet Physics and Mash Dynamics flickering with motion blur

#1

Hey guys,

As we all know, the rigid body dynamics in Maya have been lacking for a long long time. I was super stoked about being able to use physics with Mash however, essentially eliminating my primary need for C4D (quick, easy sims for Motion Graphics work). However, having used it on a recent project I ran into some issues (shouldn’t be surprised—but I had high hopes that Bullet was gonna have a solid implementation finally). Basically, it seems that the cached sims don’t handle rotation with euler rotation matrix (add to rotation, rather than reset to 0º after 359º. At least that’s what I’m assuming is happening, as things are flickering like crazy when enabling motion blur in Arnold. Ended up burning a bunch of cash on a render farm before I noticed the issues (overnight render)…

Makes me super frustrated to say the least. Anybody know how to solve this (artist friendly, rather than having to script/build a tool to fix sims and caches)?

Here’s an example;
http://imgur.com/lndpZTO

Cheers!

#2

I try and the flicker appear when the distribute node was grid. I’m doing with volume and key framing the number, and the problem disappeared

#3

Hmm. Strange… For me it doesn’t seem to matter what I do in terms of distribution mode… Sphere, Grid, Linear and so on… I suppose it might be when it’s cached where things go awry… But I have to cache for the farm to render (picking up from a different frame than frame 1 and so forth)…

#4

Hi aenrii,

I am one of the Autodesk QAs working with MASH and i am taking a look at what you described.

considering that you are caching your scene out, i am tempted to say the problem you are encountering is not on MASH, but something on the rendering side. I say this because when you cache your MASH network, MASH will generate an alembic file with the geometry. the alembic cache itself doesn’t carry motion blur information - the render engine generates that at render time (if you watch a Render sequence with arnold, you can see that the timeline jumps slightly to generate that shutter speed :)).

it also seems that you are getting a flicker even when there is no rotation addition on the geometry, which points me to something else being the cause as well.

Now i will not completely rule out that MASH could be the cause of the issue. would you be able to send us a sample file so we can try to narrow things down? I’ve build a sample scene on my side trying to reproduce what you mentioned here, but i can’t see the motion blur flickering then.

http://imgur.com/5h1bRAh

thanks for the input!