View Full Version : Bullet over Screamernet

02-22-2013, 09:07 PM
How do you bake a Bullet simulation in order to render an anim on a render farm? I know how to bake a particle sim... Save and Load PFX is right there in front of you. Same for GI. Not so, it seems, with Bullet and FFX, at least not that I can see. Searching here and the web turns up zilch.


02-22-2013, 09:37 PM
I would bake the animation to mdd files. The new mdd tool that came with 11.5 is perfect for this.

02-23-2013, 01:01 AM
the automatic dynacache files that bullet creates will be in your Content:\dynamics folder so they should be available to your farm.

Be aware that if you use mdd files on all your dynamic objects but leave the dynamic properties on them, even with dynamics disabled, then LW and the nodes will do a lot of unneeded processing, I think it loads in the now unused dynacache files.

You can test this yourself, compare the load time on your scene before and after removing all dynamic bodies

02-23-2013, 01:56 AM
Yes, MDD is the way to go. I've been using it for Bullet with rigid and cloth items with FiberFX applied. With regards to FiberFX, network renders have generally been more stable when animated with MDD as well.

And yes, remove your objects from Bullet after applying the MDD, and disable Bullet. It's pointless to have Bullet active once the items have been baked. As part of my workflow, I do my Bullet calculations in a separate scene(s) from my final render scene--this minimizes the chance of user error and can help improve calculation times. You can use Multi-Baker to speed up the MDD saving process and use the nifty new Multi-Loader tool in 11.5 to apply the MDDs to multiple objects in your final render scene.


02-23-2013, 01:59 AM
Alternatively, you can use the tools in DP Kit to save and load BDD instead. For some Bullet scenes, this may be much more efficient. I haven't used this method myself yet but if you're interested, a search in this forum should turn up more information.

02-23-2013, 02:51 AM
Isn't it possible to bake keyframes instead? Rayfire does this but its layer system also allows non destructive workflow. Mdd is very time consuming to bake and any variation of a scene takes lots of hd space.

02-23-2013, 03:03 AM
depends on what your baking, cloth and hair needs the mdd route but destroying buildings could use the bdd method to save lots of hd space

02-23-2013, 03:35 AM
What he said. ;)

02-23-2013, 04:51 AM
Good to know. Editable keyframes per piece and I hope the dynamics to morph trick also work with bullet.

03-23-2014, 10:53 PM
The BDD Scan from DP bakes parts of the objects as individual pseudo objects. As such the filesize is a lot smaller than using MDD. And probably Motion Blur would be mor correct.

Motion Blur with MDD is generally not correct. It's just linear. You can use spline interpolation for the vertices with some of the MDD readers, but when an object is spinning too fast for example MDD motion blur would be a total Mess.

One thing I have found is that the Bullet dynacache produces perfect motion blur. However, bullet handles it all by itself with no user control. One minor change and you lose your cache forever. It should be able to save those caches for rendering purposes.