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how to apply mocap data (keyframed nulls) to a model
Posted: 01 August 2017 01:23 PM   [ Ignore ]  
Total Posts:  2
Joined  2016-08-23

hello, I have been sent some mocap data to test out for a concept. it is in a .c3d file. I was able to convert that to an .fbx to bring into cinema 4d. it comes in as a bunch of nulls. how can I take those nulls and have a model animated to them?

I’ve worked with the mixamo mocap files and I get how to attach a model to those. but how can I get this series of nulls into a skeleton of joints?

any help would be appreciated.

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Posted: 01 August 2017 02:17 PM   [ Ignore ]   [ # 1 ]  
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Hi jwebboil,

Since I can’t see the Nulls, and how they are set up, here are some pointers.

Select all, (except for the Parent Null perhaps), then
Main Menu> Character> Conversion> Convert To Joints.

Find the T-Pose, of the “Skeleton” and the Character, eventually scale one or the other, perhaps both, so they match.

Select Mesh and joints
Main Menu> Character> Commands> Bind.

With Main Menu> Animation> Add Motion Clip… you can bring the different “takes” together. See some tips in the new Mixamo Training here on Cineversity.

For more information, go to the Tutorial section, then to Instructor, and click on the name Bret Bays.
Browse the list of his tutorials and have a look what might be useful for you.
What you ask to do, is pretty much a complete Rigging course, but I’m not clear what you know or not.

Perhaps you can share the object and at least two of the Mocap data sets, then I can look into it, but I certainly need a T-Pose of both.

If you feel completely overwhelmed at the moment, and time is not really given for that project, perhaps you check in for and 1on1 session to get this done.

All the best

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Posted: 01 August 2017 02:33 PM   [ Ignore ]   [ # 2 ]  
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Joined  2016-08-23

Thanks for the info. the “convert to joints” command really seemed to get me almost there. my issue now is that when i select the nulls (they aren’t in a hierarchy- each one is keyframed from the mocap data) and select “convert to joints”, i get the joints but they don’t have the motion form the nulls. what is the workflow to carry over the animation to the joints? also is the fact that the nulls are not in a hierarchy going to be an issue? if so how should i deal with that?

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Posted: 01 August 2017 02:40 PM   [ Ignore ]   [ # 3 ]  
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Thanks for the additional information, jwebboil.

The Nulls should be in a Hierarchy, and perhaps the position shows how the hierarchy should be. I would do that before.

Anyway, without seeing anything, this is not a way to go, it would be a ping pong of guessing, not what I like to do here.

Perhaps you share a link and send it to my Private Message here on Cineversity.

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 01 August 2017 06:55 PM   [ Ignore ]   [ # 4 ]  
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Thanks for the files, jwebboil. As usual, it speaks a clear language and we can stop guessing around. Thank you very much! This is not a useable rig so far, it needs a spatial and a hierarchically translation. In other words, the mapping of the MoCap data to a skeleton is missing.

I check the books “The Art and Technique of Matchmoving” Erica Hornung and
“Matchmoving” Tim Dobert, 2nd
Both have no answers to this.
I remember a course on FXPHD (and earlier to that over at PXC) about it that I took nearly a decade ago, but it is not longer on their site[s]. So, no luck here either.

If someone follows the thread, just let me tell what I got as files:
Similar to this suit
http://www.cgw.com/images/Media/PublicationsArticle/pg12a_1.gif
(which I took randomly from the web)
the white tracking markers are the nulls that the file contained. All tracking points are just siblings, no naming, no hierarchy, no differentiation at all, besides a sequential numbering of the elements.
Typically a mocap studio has an application to “translate” or better “map” these dots onto a standard joint/bone rig. To give you just these files seems kind of unusual. Unusual, as they have normally the tracking dots as a “preset” in such an application. 
I haven’t used Motion Builder since a decade, it has these options. But have a look here:
https://www.youtube.com/watch?v=ocBg4j-wgAc
https://www.youtube.com/watch?v=n3WY_1hxP1A

My suggestion would be,

a) ask them to give you the mapped up files, in form of a rig.
b) get a different service provider who can translate this, a company who uses the same suit, etc.
c) check with other offerings if they have something that matches your current needs. I checked Maximo, but I couldn’t find something adequately like the hockey player, but look for yourself, for a short moment things are free on Maximo!
d) invest some work and go thought that

I have nothing to offer about a) to c), while c) has its own series here at the moment.

The option d) seems the least favorable work without specialized software, (e.g., Motion Builder), and it is no secret, this is a lot of work if done manually. The dots on a suit are not where the Joints should be. In other words each point of that cloud needs to be identified (what is it and where in the hierarchy would it be …) and in case of the hockey stick, it needs a separation. Then you might find the distance/orientation and so the location of the joint needed to create the skeleton. If that works out nicely, perhaps it works after a while. To get the Nulls “constrained” with the joint rig of the figure, while Xpresso is used to streamline the process for more adaptations (takes).

I might miss something, but what I can say with certainty, Cinema 4D has no native tools to do this quickly or comfortable.

Sorry to be of no real help, thinking about solutions.

Let me know, if there is anything else.

My best wishes

Updated/edited Aug 02

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

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