Help needed on fixing sliding feet in mocap data

[mbreidt]

We have long (5 min.) mocap data sequences (from an intertial mocap system) that exhibits feet sliding. Now I wonder what the best way would be to correct this in MotionBuilder?

Being a fairly new user, I found the floor contact parameters, and they adjusted the lower body parts such that the feet/toes will not penetrate the ground plane, but they did not remove the very noticeable lateral sliding. Any ideas how to make the feet more 'sticky'?

And another, related question: Say, you have a mocap sequence, and add manual adjustments to it (e.g translational offsets to the hip to compensate for drift in the mocap data), which will then cause foot sliding, what would be the best way to get the feet to lock to the ground when they touch it?

Isn't there some function in MotionBuilder that will detect foot contact with the ground and create a 'planted foot key' lasting as long as the ground contact was found in the data?

Thanks in advance for any comments
-- MartinB

[_neill_]

Hi,

there is some fixing sliding feet algorithm in MoBu - Feet Stabilization in Character Settings tab / Retargeting / Actor / Feet Stabilization

Also for fixing feet sliding I have using aux effector and pivots... actually, aux. effectors with animated weight in some case is equal to the "planted keys"

[_neill_]

I have written small tutor about that. You could find it here - http://neill3d.com/ustranenie-skolzheniya-nog?langswitch_lang=en
Hope that helps.

[mbreidt]

Hi,

there is some fixing sliding feet algorithm in MoBu - Feet Stabilization in Character Settings tab / Retargeting / Actor / Feet Stabilization

Thanks for the help, and also thanks for the tutorial, which looks very useful!
Unfortunately, those settings don't do anything with my data. It is very likely I am missing something very basic, but I cannot figure out what...

So here's what I do:

I import the mocap data from a BVH file, set up the character definition and characterize. Then I set up the parameters in the Character Settings, such as Floor Contacts for feet and toes, and the parameters you showed me under Retargeting - Actor - Feet Stabilization to the best of my knowledge. The mocap data will not be affected at all by this, so I figured I have to create a control rig, which I do (FK/IK). Next, in order to get my original data into the control rig, I plot it into the control rig and activate the control rig input. Is this correct so far?
Having done so, the feet react to the floor (when I move the ground plane up, for example), but I don't see ANY effect that reduces sliding.

What am I missing here?

Thanks!
-- MartinB

[_neill_]

Try to set Stabilization weight on stage when you have character with input animation from actor... There might be some dumping jittering when your increase stabilization... but dont mention it, it's just preview... so plot on control rig and that's it. About stabilization params, there is some information in help

[_neill_]

Try to set Stabilization weight on stage when you have character with input animation from actor... There might be some dumping jittering when your increase stabilization... but dont mention it, it's just preview... so plot on control rig and that's it. About stabilization params, there is some information in help

P.S. Sorry for double post, connection trouble...

[mbreidt]

Try to set Stabilization weight on stage when you have character with input animation from actor...

Not sure I understand. I have prerecorded motion data, saved as BVH file. How do I get that onto an actor?

Also note that I edited the above post, because I used some characters that made the first half of the 'what I do' paragraph disappear, sorry for that.

Thanks again
-- MartinB

[_neill_]

If you have prerecorded skeleton animation which you retarget onto a character, feet stabilization algorithm is not avaliable (only for actor retargeting). The only way for actor stabilization is to create a set of markers for each skeleton bone, parent that markers to each body part... then add actor to a scene and setup him with a new markers. This gives a possibility to transfer skelet animation to an optical one. After that you could transfer from an actor to a character and active stabilization mode...

[mbreidt]

If you have prerecorded skeleton animation which you retarget onto a character, feet stabilization algorithm is not avaliable (only for actor retargeting). The only way for actor stabilization is to create a set of markers for each skeleton bone, parent that markers to each body part… then add actor to a scene and setup him with a new markers. This gives a possibility to transfer skelet animation to an optical one. After that you could transfer from an actor to a character and active stabilization mode…

Thanks a lot - and wow! this sounds really complicated for such a (apparently) straight forward task. So I need to 'invent' optical markers, which then will be used to reconstruct (hopefully!) the same skeletal data, only in a different format, which then can be used for feet stabilization?!

By the way, where is the best place to learn these basic data flow concepts of MotionBuilder: actor vs. character vs. skeleton vs. plotting. I found the online help to be more of a reference manual than a user's guide, and most tutorials concentrate on keyframe animation, not motion capture data.

Thanks again!
-- MartinB

[_neill_]

Yes, feet stabilization is only supported by an actor. But to tell the truth It's so fantastic way out and it's really old algorithm to do all the convertions manually. If you have a possibility to automate convertions process, feet stabilization will be usefull, in other case, as for me, it's better to correct sliding by hand (as I show at a video). Actually, I solve feet sliding by hand.

[mbreidt]

Yes, feet stabilization is only supported by an actor. But to tell the truth It’s so fantastic way out and it’s really old algorithm to do all the convertions manually. If you have a possibility to automate convertions process, feet stabilization will be usefull, in other case, as for me, it’s better to correct sliding by hand (as I show at a video). Actually, I solve feet sliding by hand.

Well, we have 24 sequences, each 5 minutes or longer. Doing that by hand will be extremely slow (and boring), I guess. So I was looking for a way to do this automatically.

Before looking into MotionBuilder, I tried using Character Studio's footstep extraction, but that also failed pretty badly. I am really surprised such a function (locking down foot sliding) does (almost) not exist....?

-- MartinB

[BradClarkRiggingDojo]

Most good capture systems keep the feet locked down and why there have not been much advancement on the process.

Your best bet is to build the virtual market set once, hook up the actor and then just import all the 24 moves in as takes on that rigged up skeleton so you can process them all at once.

Or go back and ask for the optical data instead of a skeleton.(they should have done basic foot stabilization if they were processing it down to a skeleton for you.)

Brad.

[mbreidt]

Most good capture systems keep the feet locked down and why there have not been much advancement on the process.

Unless you're using an inertial motion capture system, I guess. Which is where this data comes from.

Or go back and ask for the optical data instead of a skeleton.(they should have done basic foot stabilization if they were processing it down to a skeleton for you.)

See above, there never were any opticals.

The inertial system tries to compute full skeletal data from acceleration and contact point detection, but obviously it had trouble in this case to fully accomplish this. Additional foot sliding is introduced when editing was made to correct for positional drift in the data, i.e. repositioning the hip in order to get the talent lined up with some other 3D elements.

Initially the plan was to use Character Studio's footsteps for all this, but that did not work at all (or we were too stupid to get it working). So we looked into MotionBuilder.

Again, "all" I want is a mechanism that detects the proximity of the feet to the floor, and as long as they don't move within a certain threshold, they will be locked to the ground. This might cause some unnatural leg movement in some cases, but not as bad as the whole figure skating around. ;-)

Martin