Current state of BVH imports

[sinisterchipmunk]

Hi,

I consider my skill to be slightly below intermediate with Blender (I can make stuff but am rarely satisfied with the result; I understand the interface but frequently can't figure out how to perform some action) and have spent the past few days coming up to speed with MakeHuman. I am very impressed!

I've managed to export a character in MHX format, import it into Blender, and render it. I now understand the rigging and the basics of animation. I've even modeled a little bit of clothing that I hope to contribute at some point, if it's good enough. I'm still having trouble exporting it to MakeHuman but that's a different topic, and I think my settings are just incorrect.

The thing I've been entirely unsuccessful with so far is the BVH import. The API seems to be in flux because the various blogs, forum posts and documentation that I've found reference flags and options that don't appear in my instance. I am trying to import any BVH file I can find: I've tried some of the CMU files (max, daz and mb formats) and some of the ACCAD files. In the best case, the animation seems to play more or less correctly, except for a strange "jitter" as if my character has had a lot of caffeine; this is most noticeable in the hands. In some cases the arms and/or feet are backwards; and in extreme cases the animation is completely garbled.

I should note that the BVH importer has done a good job (except for the jittering) with most of the animations when left with the default settings. The backward limbs and garbled results are mostly due to my own blundering with the various import options.

I understand that I am using a development build and it's probably considered unstable. Therefore, my questions are:

1. Is the behavior described above the expected result given the current state of the code base?
2. How can I achieve a nice, smooth animation instead of the jitters? Should I import the BVH as I have already done and then tweak the result frame by frame, or is there a better way?
3. Should I be using any particular BVH format or repository? Can anyone share a link?
4. Is there anything I should be aware of in terms of changing the default settings and flags?

Additionally, I've also experimented with using the standard Blender BVH importer. It appears to import the animation properly. I noticed the "Retarget Selected" (or similar -- I'm typing this from memory) button in the MHX options, but I can't get it to work. It always gives me an error about the armature, the text of which I can't remember at this time. Does this button do what I'm trying to make it do? And, does it actually work at this time?

For the record, I've been entirely unsuccessful at getting any usable result when using Blender's built-in retargeting system, but this may be more due to operator error than the system itself.

I'm using Blender v2.63.

Thanks in advance for any assistance!

[ThomasL]

There is extensive documentation about the MH mocap tool at http://www.makehuman.org/node/285

The best button to use is normally Load and Retarget. The buttons below that do partial tasks. To use the Retarget Selected to Active button, you first need to import an animated armature with Load and Rescale BVH File.

The standard BVH importer does essentially the same job as the Load BVH File button; it creates an animated armature. The difficult task is to retarget that animation to a given armature, with different proportions and rest pose.

Jitter is usually due to poor animation data. IIRC, the early CMU files are quite noisy, the later ones are better. It is unlikely, although not entirely impossible, that the Mocap tool introduces noise of its own. The same operations are applied to all frames in the animation, which may lead to systematic errors but hardly to noise.

There is a list of sites with free bvh files in http://www.makehuman.org/node/288

[ThomasL]

I noticed a bug in the retargeting of the mhx rig; the rig has apparently changed since last time I checked the mocap tool. The upper arms have weird positions, but if you set the Left and Right ArmHinge properties in the MHX Drivers panel to 1, things look better. WIll look into this.

[ThomasL]

The hinge problem has been fixed in svn.

[sinisterchipmunk]

Thank you very much for your replies!

IIRC, the early CMU files are quite noisy, the later ones are better.

That's great news, maybe I just had the wrong source files! I'll play with it more this weekend.

Thanks also for the links, and the bugfix.