Skeleton calib necessary with MotionBuilder?

[Pixerati]

Since we're just applying markers to the MotionBuilder skeleton within MotionBuilder, do we actually need to perform the skeleton calibration in Arena? Could we just create generic rigid bodies from the markers to bring them into MotionBuilder?

Also, do the markers only come across to MotionBuilder if they're included in a rigid body? I.e. can we just bring a point cloud into MotionBuilder and assign the points to an actor there?

Thanks.

[seanboyette]

Pixerati -
Technically you could create an set of rigid bodies.
I assume that your goal may be to do a variety of characters - and yes it could be done. If you are doing a biped, why not use the skel, its easier than the creation of all of the rigids.

Sean

[Jim]

Hello:

In Arena, a skeleton or rigid body is needed to define the markers and label them, they are all linked, you can't do one without the other. The markers will come across as a labeled point cloud into MB, if using the plug-in, or similarly with C3D.

It is very easy to do a skeleton setup in Arena, like less than a few minutes once you have the hang of it.

[seanboyette]

Hey Jim/Pixerati,

I think the question is COULD you simply create a set of RB's and export them, possibly for the creation of your own structure/skel (Pixerati, please correct me if I am wrong) - and the answer is certainly yes.
I mean you could create the rigids that define a dog or some other non biped character if you wanted and export that point cloud to mb via c3d. I may to think about this and try to export some data from my dog!

Exciting! man I will have to try this out!

Sean

[Pixerati]

Exactly, or, just as importantly, create a skeleton with more markers for improved tracking during occlusion.

[Jim]

I suppose you could do that, but you would lose all the extra tracking help you get from having a defined skeleton, but for the dog, I totally get that, can't wait to see that demo video!

For adding more markers to help with occlusion, you can do that now, by manually adding markers and assigning them to bone segments. You just can't use the skeleton wizard to do it. In a future release we will probably automate that more, and add in a 45 marker default skeleton.

[Pixerati]

So - forgive my complete ignorance - MotionBuilder is still using Arena's skeleton tracking, even though we're assigning points to the MotionBuilder actor skeleton? I'd assumed that Motionbuilder was just looking at the labeled points coming from Arena and ignoring their skeletal relationships.

Also, just have to say, having worked on many high-end software packages over the years - in and out of beta - I'm blown away by the quality of your 1.0 release. Lack of documentation aside, it's rare (can't think of another in recent history) to find a V1.0 app that works so well, is so stable, and with such intuitive wizards.

[Jim]

Hello:

- You are right, MotionBuilder only sees the cloud of labeled points and you must apply them to the MB skeleton. But... to get the labeled points in the first place, inside Arena, you must have a rigid body or skeleton defined in Arena to actually track the markers in the first place, and therefore label them, otherwise they are a cloud of unlabled points and can change their labeling from frame to frame.

Thanks for the nice comments on Arena. Yes, still working on the old manual.

[leith]

hrm... I think I've just figured out what my next topic on my blog will be...

Theory of rigid and kinematic model tracking. I sense confusion.

[leith]

first entry done:

http://blog.fie.us/

It half answers the issues in this thread a bit. The next entry should finish up the remaining issues. Specifically: why, although you could do a human with individual rigids, its better to have a hierarchical skeleton with limited joint rotations.