Modifying BVH mocap rigs to fit character... Help!

[evolross]

I've been trying to figure out what the process is for modifying raw BVH mocap files to fit into a character's mesh. I want to simply use the same rig as the BVH, but have it fit my character (NOT re-target it). I'm using the method from Larry Shultz's Mocap DVD from Kurv where you make just a base rig from a BVH file so that you can quickly load in other motions from the same library using "Merge Envelopes" or IKBoost. The problem is whenever I do the merge or copy the motion, the skeleton and resulting motion is all jacked up.

Using any of the bone tools to fit the base rig to my mesh (e.g. Joint Move, Tip Move, or God forbid Scale Hierarchy) causes bad results. And actually rotating the bones and modifying Rest Lengths to fit my character mesh causes bad results.

The DVD and most threads show people fitting their characters to the BVH rig or having a character that already fits... a standard 6' tall human.

What's the right way to do this? Can it be done without Motion Builder or Animeeple?

[RebelHill]

well, it should jsut work... reposition the bvh rest pose into your character, and the motion should play just fine from there... There's a couple things that can get in the way... recording pivots is ofc a big no no... also, if you're using one bvh scene to be the base pose, and then loading motions from others onto that there could be mismatches, and even though they're in the same library, they may not necessarily be using the same setup, in terms of base rotations, hierarchy names, order, etc.

Tbh though, I cant think why you wouldnt want to retarget the motion, not doing so will just give you a ton of foot slip and other errors related to differences in proportion... animaeeple is free after all, and also, if you're not wanting to shell out the $50 for the fbx exporter, you can just export as collada, and use the autodesk fbx converter (also free) to convert to fbx, and you can then bring those motions into LW just fine, (so long as you're using V10 that is).

[evolross]

I'm using the same motion file as the base rig. I can't get even one to work well. Does using Tip Move, Joint Move, and tools like that do a record pivot rotation? Everytime I do Load Items Motion Envelopes or an IKBoost copy, the rig I modified changes and nothing is rested right.

Yeah I watched your videos on MotionBuilder and Animeeple and that works fine. I got Animeeple to work with the DAE converter with free Animeeple motions from their store. However, I can't get an imported BVH in Animeeple to come back out correctly. The legs are crossed, things are inversed, and it's just generally wacky... however the same BVH file works fine imported into the MotionBuilder and comes out clean and nice.

Basically I'm trying to find an easy, non-expensive roundtrip method for BVH and Lightwave. I'm using the demo of MotionBuilder.

[MaDDoX]

I'm using the same motion file as the base rig. I can't get even one to work well. Does using Tip Move, Joint Move, and tools like that do a record pivot rotation?
No.

however the same BVH file works fine imported into the MotionBuilder and comes out clean and nice.
That would hint to me that Animeeple is somehow changing the BVH rig. Why don't you try using an Animeeple-exported rig as your base rig in Lightwave then, before round-tripping it?

Basically I'm trying to find an easy, non-expensive roundtrip method for BVH and Lightwave. I'm using the demo of MotionBuilder.
Yeah, that's how I do it. The more I check other rigs, the more I realize that I'm 100% spoiled by MotionBuilder :( I'm seriously considering to force myself into making an animation in a standard Lightwave rig just to fell less "alien" to the standard animation discussions. I actually find it very weird when people say Mobu's rig "is not good for animation", guess it just became second nature to me.. :o

Anyways, slightly off-topic, hope my former idea works for ya.

[evolross]

So I exported a motion out of Animeeple, brought it into LW10, stripped off the motion and fit it to my character, rested the bones, I then did a "Save Trans Object" on my object, swapped the new mesh in, and set all my bones to rotation 0, 0, 0 which gave me the first attached image.

I exported this via FBX, brought it into Animeeple, brought in a BVH from the CMU library (02_01 to be exact) and again, I get the criss-crossed legs and general funkiness, see second image. It's the same exact result I get as using RebelHill's FBX rig. I also tried it on a different BVH in the same library and I still get the criss-crossing on the legs.

Again, works fine in MotionBuilder. Also, any motion from Animeeple's store works great... so it's definitely doing something to the BVH or getting confused. Maybe I'll try to submit this to them.

[evolross]

I submitted my files to Animeeple and Leslie quickly figured out the issue. The criss-crossed legs were due to the fact that the CMU's BVH library (or at least the files I tried using) don't have the same T-pose that Animeeple uses. The CMU files have the legs spread apart on the T-pose frame, which is probably what MotionBuilder likes. This is reinforced by the fact that I was using the files from the CMU library that were specifically converted for use in MotionBuilder :foreheads.

To fix the issue, when importing the BVH into Animeeple, you simply adjust the rig on the "TPose" tab to match what Animeeple likes. Finally, free round-tripping of 3rd-party BVH files in Lightwave, that actually work nicely. Though I may buy the FBX exporter plugin just to support Animeeple.

[RebelHill]

Aha... well that solves it...

MB does have much the same thing, where it interprets whatever base pose you put in as though it were "perfect T" for that character, the result being that all motions are tranferred relative to that. So if the arms are at a 45 deg angle in the base pose you send to MB, then they'll poke into the body when meant to be at the sides, (rotating 90 deg down from base pose), etc.

[evolross]

Well Motion Builder didn't seem to mind the CMU BVH file starting with the legs spread out versus straight down. It re-targeted the walk cycle perfectly. And additionally, that set of CMU BVH files say they're converted specifically for Motion Builder. Maybe MB is smart enough to resolve the legs in either position...

[RebelHill]

It could well be...

Afterall even though I say, MB expects this pose, it does have plenty of tools in it for offsetting motion, and manually dictating how the retargeting behaviour will work for any given body part, so its quite possible that the legs, possibly being a common one, are handled much more automatically.

[mrbones]

Visit http://www.truebones.com

or http://www.animstreet.com

They may be able to help.