[ros-users] Skeletons

Marcus Liebhardt marcus.liebhardt at pal-robotics.com
Sat Mar 26 22:27:20 UTC 2011

Hi there!

That indeed looks like a tree to me.
I would be interested in the use cases you have in mind for these skeleton
What information would you like to gather in those messages?
Poses of the tracked frames, interconnections of each frame, also distances
between the connected frames?

I don't have deep knowledge about the processing of the KInect or the
openni_tracker. I'm currently just using the transforms. But I think there
are simplifications made for some frames, which could be useful to take into
account. For example, I think the neck is always half way between the left
and right shoulder, and the head is always on top of it. Things like that
might be interesting as well to keep in the message, so that one can easily
reproduce the previously mentioned skeleton - if that is one of the use

Best regards,

:-) Marcus

2011/3/26 Patrick Goebel <patrick at pirobot.org>

>  I see what you mean--the user looks more like a cactus than a tree. :)))
> However, I think if you take the torso joint as the root, don't you end up
> with a tree structure?  e.g.
> torso->neck->head
> torso->left_shoulder->left_elbow->left_hand
> torso->right_shoulder->right_elbow->right_hand
> torso->left_hip->left_knee->left_foot
> torso->right_hip->right_knee->right_foot
> Maybe this is what you meant by it depends on how you define them.
> --patrick
> On 03/26/2011 12:22 PM, David Lu!! wrote:
> It depends on how you define them. The skeleton visualized with the kinect
> (
> http://www.ros.org/wiki/openni_tracker?action=AttachFile&do=get&target=nite.png)
> isn't a tree, although it could be converted to be one, I suppose
> On Sat, Mar 26, 2011 at 1:11 PM, Patrick Goebel <patrick at pirobot.org>wrote:
>>  Hi David,
>> I agree it would be nice to have a standardized Skeleton message.  If all
>> skeleton's are trees (is this true?) then perhaps an existing tree message
>> type could be used if it exists.  KDL has kinematic chains and tf is already
>> built around trees (right?).  That's about as far as I've thought it
>> through...
>> --patrick
>> On 03/22/2011 04:17 PM, David Lu!! wrote:
>>  Hey Ros-users-
>>  Has there been any talk of creating a standardized Skeleton message?
>> Right now, it seems like the openni_tracker package just publishes
>> transforms. It seems like if the Kinect does skeleton tracking, there should
>> be a skeleton message.
>>  I know pi_tracker has its own Skeleton message, which looks like it
>> might fit the bill, although I don't think it defines which parts are
>> connected (hip bone is connected to the thigh bone).
>>  http://www.ros.org/doc/api/pi_tracker/html/msg/Skeleton.html
>>  It might be good to have for not only the Kinect, but for other motion
>> capture rigs (Vicon and the like).
>>  Are there any other similar message out there?
>>  -David!!
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