ROS Resources: Documentation | Support | Discussion Forum | Index | Service Status | Q&A
Ask Your Question

ar_pose rotate transform without image rotation

asked 2013-04-27 10:42:16 -0500

davinci gravatar image

updated 2014-01-28 17:16:22 -0500

ngrennan gravatar image

I have an urdf description of a camera on a robot. On the camera I run the ar_pose detector. The image is correct, but detected location is behind the camera. The problem is that if I change the origin in the urdf the image gets also rotated. How can I get the image and the marker position correctly simultaneously?

image description

edit retag flag offensive close merge delete

1 Answer

Sort by » oldest newest most voted

answered 2013-05-08 11:01:10 -0500

Procópio gravatar image

In my experiments, the camera points in the direction of its blue axis. So looking at your frames, it looks like your camera is actually pointing upward. Try to correct that in your URDF and then, if your image is rotated, you can always rotate your camera frame around the blue axis until you get it right.

edit flag offensive delete link more


Thanks for your response, but the camera image obtained at the red axis. Rotating the axis so that the blue axis is in line with the arm means that the camera is pointing downwards like this:

davinci gravatar image davinci  ( 2013-05-10 02:29:02 -0500 )edit

actually that image only confirms that the blue axis is pointing in the direction of your field of view. If it was the red axis, you would see the grid as squares, but instead you see them in perspective. Also you can see the axis just in front of your camera in the image (/arm_shoulder_pivot).

Procópio gravatar image Procópio  ( 2013-05-10 03:13:24 -0500 )edit

just rotate your camera frame once more, maintaining the direction of the blue axis, until you can see your floor grid in the base of the camera image (in your camera window). I think the green axis must point downwards. after that, check if the marker position displays correctly.

Procópio gravatar image Procópio  ( 2013-05-10 03:18:37 -0500 )edit
davinci gravatar image davinci  ( 2013-05-10 05:04:14 -0500 )edit

ok, now you got your camera rigtht (by the position of the floor and by the arm's joints in your cam image)! I think the problem now is with your Rviz object. Maybe you are creating your Rviz object with the wrong orientation? Check your code when you create the Rviz marker orientation.

Procópio gravatar image Procópio  ( 2013-05-10 05:19:26 -0500 )edit

..Got it thanx

moonlake gravatar image moonlake  ( 2013-06-02 21:14:34 -0500 )edit

How did you solve it then?

davinci gravatar image davinci  ( 2013-06-02 23:59:23 -0500 )edit

sorry @davinci, do you mind adding the images from the comments here to the question part (upload to in this way the question would become more informative for future reference and we would not depend on your dropbox. thanks!

Procópio gravatar image Procópio  ( 2013-06-03 00:07:35 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools


Asked: 2013-04-27 10:42:16 -0500

Seen: 366 times

Last updated: May 08 '13