My collegue Ingo is working on an improved version of ARToolkit Plus for the ros community, so if you can wait a few weeks, things might get better. (subpixel accuracy, adaptive thresholding etc.) Generally, ARToolkit is not too good, its not estimating subpixel-accurate and only taking the 4 outer corners for the estimation of the homography. So you should expect the orientation to jump a lot. Additionally, the distance will be pretty noisy and have a systematic dependency on the shutter, gain and your threshold, as only the outside edge from white to black is taken into consideration. I worked with 12.5x12.5mm ARToolkit markers to detect drawer and cabinet handles for a week or two, using PR2 forearm camera (we now have some pcl method for detecting handles). This worked, but I wouldn't bother looking at the orientation you get. Sometimes the orientation jumped between something reasonable and 'the marker pointing directly to the camera'. I had to filter this out and then averaged over 20 frames or so and would still end up with around +-3 cm distance error and a bad orientation. Watch out - averaging quaternions is not necessarily trivial. The markers were however very small, maybe 1% of the image area or even less. Tom from TUM On 11/08/2010 05:10 PM, Eohan George wrote: > I think its a known problem about artoolkit .. this link Robust Pose > estimation from planar target > mentions > some of those.. > The artoolkitplus has a robust pose estimate api which "reduces" this > problem. However, I did see this issue to a smaller extent even with > rpp. I am not sure if I was using it the wrong way though. > > Eohan > > On Mon, Nov 8, 2010 at 10:47 AM, Ivan Dryanovski > > wrote: > > Steven, > > I'm not sure if this is exactly the problem you are observing, but I > have noticed a similar behavior from ARToolkit before. When the camera > is nearly perpendicular to the marker, and the marker is in the center > of the image, there occurs a singularity. Let's say the angle between > the marker normal and the optical axis is 1 degree - ARToolkit will > arbitrary flip between +1 and -1 degrees. If you make the angle > bigger, the orientation of the marker becomes less ambiguous, and the > error diminishes. > > Ivan Dryanovski > > On Mon, Nov 8, 2010 at 9:00 AM, Herman Bruyninckx > > wrote: > > On Mon, 8 Nov 2010, Steven Bellens wrote: > > > >> 2010/11/8 Steven Bellens >: > >>> Hi, > >>> > >>> I'm experimenting a bit with the ar_pose package. I'm using a > single > >>> fixed camera to track a moving marker. To verify the estimation > >>> accuracy, I just leave the marker fixed and I've plotted > position and > >>> orientation estimates. The position estimates are pretty much > >>> constant, but the orientation estimates are oscilating a lot (see > >>> appendix), and apparently always between two values. Is this > because > >>> of the bad capability to estimate that orientation or can this be > >>> caused by the environment conditions (light - set-up - distance to > >>> marker)? > >> > >> For clarity, plotted are the 4 components of a unit quaternion. > > > > So...? What does a jump of "0.1" quaternion units mean? And is > this meaning > > the same for each of the four components? > > > > The answer to this last question is probably "no", hence...? > > > > Herman > > _______________________________________________ > > ros-users mailing list > > ros-users@code.ros.org > > https://code.ros.org/mailman/listinfo/ros-users > > > _______________________________________________ > ros-users mailing list > ros-users@code.ros.org > https://code.ros.org/mailman/listinfo/ros-users > > > > _______________________________________________ > ros-users mailing list > ros-users@code.ros.org > https://code.ros.org/mailman/listinfo/ros-users >