Arena bvh export - control over axes and rotation order

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smguest
Posts: 3
Joined: Wed Sep 14, 2011 2:52 pm

Arena bvh export - control over axes and rotation order

Post by smguest »

I'm fairly new to the motion capture arena (but not to 3D graphics) and need to export motions captured in Arena to Boston Dynamics' DI-Guy. Their motion editor will import bvh files but I've discovered two problems -

1) DI-Guy expects the shoulder angle to be arms straight down (not out to the side as in a T-pose).

2) The coordinate axes are different and therefore the rotation order is different.

Is this something I have to handle via postprocessing the bvh file or are there some configuration options within Arena that will let me account for these differences?
NaturalPoint - Mike
Posts: 1896
Joined: Tue Feb 01, 2011 8:41 am
Location: Corvallis, OR

Re: Arena bvh export - control over axes and rotation order

Post by NaturalPoint - Mike »

What difference is there in the coordinate axis that it expects? Is this just a left hand/right hand thing?
smguest
Posts: 3
Joined: Wed Sep 14, 2011 2:52 pm

Re: Arena bvh export - control over axes and rotation order

Post by smguest »

It is actually a change in the coordinate system (X forward, Y left and Z up, with a ZXY rotation order) but it isn't clearly documented so I'm trying to get that confirmed with Boston Dynamics. When I first brought this question up to them, we focused on the fact that the shoulder positions at zero rotation were different and they suggested it would help if I could capture the data with the same reference of arms straight down as zero deflection, so that is why I asked. I'm now thinking the problem is bigger than that.

I'll post more info as I get it.


Thanks!
smguest
Posts: 3
Joined: Wed Sep 14, 2011 2:52 pm

Re: Arena bvh export - control over axes and rotation order

Post by smguest »

Boston Dynamics states that their importer should handle the rotation order and it is the difference in the zero position of the arm that is the problem. Looks like you can't just add a 90 degree offset to the motion capture data since it also rotates the axes?

So back to the original question, any way to set up Arena such that it reports zero degrees rotation (in the exported bvh file) for the shoulder joint with the arm straight down (instead of out to the side)?
NaturalPoint - Mike
Posts: 1896
Joined: Tue Feb 01, 2011 8:41 am
Location: Corvallis, OR

Re: Arena bvh export - control over axes and rotation order

Post by NaturalPoint - Mike »

At current, no, but I've passed this on to our development team to take a look at for a future release.
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