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