Hi Ugo,
That sort of query looks right.  It will give you the latest available
transform from the "/threemouse" frame_id to
the "/sr_arm/position/shadowarm_handsupport" frame.  Without more
information on the setup of your tf frames I cannot say if you're getting
the right transform.  I will note that "/"s in frame_ids do not scope the
same way as namespaces. If you post the output of view_frames I can help you
more.

Tully

On Tue, Sep 21, 2010 at 7:08 AM, Ugo Cupcic <ugo@shadowrobot.com> wrote:

>  Hey,
>
> I'm trying to implement some reverse kinematics on a custom arm, in
> order to move the arm using a 3D mouse.
>
> I want to compose 2 transforms: my 3D mouse is publishing tf transforms,
> and I have the tf published by the robot_state_publisher for my arm. I
> just want to get the resulting transform: move from the current position
> to the current position to the new position (current position +
> transform from the mouse).
>
> I was using this but I think it doesn't do what I want.
>        tf_listener.lookupTransform("/threedmouse",
> "/sr_arm/position/shadowarm_handsupport", ros::Time(0), transform);
>
> Sorry if it's a trivial question :S
>
> Cheers,
>
> Ugo
>
> --
> Ugo Cupcic         |  Shadow Robot Company | ugo@shadowrobot.com
> Software Engineer  |    251 Liverpool Road |
> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487
> http://www.shadowrobot.com/hand/              @shadowrobot
>
> _______________________________________________
> ros-users mailing list
> ros-users@code.ros.org
> https://code.ros.org/mailman/listinfo/ros-users
>



-- 
Tully Foote
Systems Engineer
Willow Garage, Inc.
tfoote@willowgarage.com
(650) 475-2827