OpenCV Q&A Forum - RSS feedhttp://answers.opencv.org/questions/OpenCV answersenCopyright <a href="http://www.opencv.org">OpenCV foundation</a>, 2012-2018.Wed, 11 Dec 2013 03:50:51 -0600solvePnP not giving identityhttp://answers.opencv.org/question/25030/solvepnp-not-giving-identity/Hi,
I'm trying to understand how solvePnP really works. I use a kinect camera to get SIFT keypoints and the corresponding 3D points.
I give the 2D/3D couples to solvePnP and I expect it to give me the identity matrix as this is equivalent to stare at the same scene without moving.
Result : though the rotation part is the identity, I get a strange translation vector : [0.05, 0.1, 0.8]. These values seem too large, and I can't understand why the Z part is so big compared to the others.
Overall the result is wrong as I get a huge translation along Z.
Any idea as to why this happens ?Thu, 05 Dec 2013 08:47:26 -0600http://answers.opencv.org/question/25030/solvepnp-not-giving-identity/Comment by Guido for <p>Hi,</p>
<p>I'm trying to understand how solvePnP really works. I use a kinect camera to get SIFT keypoints and the corresponding 3D points.
I give the 2D/3D couples to solvePnP and I expect it to give me the identity matrix as this is equivalent to stare at the same scene without moving. </p>
<p>Result : though the rotation part is the identity, I get a strange translation vector : [0.05, 0.1, 0.8]. These values seem too large, and I can't understand why the Z part is so big compared to the others.</p>
<p>Overall the result is wrong as I get a huge translation along Z.</p>
<p>Any idea as to why this happens ?</p>
http://answers.opencv.org/question/25030/solvepnp-not-giving-identity/?comment=25284#post-id-25284The whole problem was due to calibration issues. The kinect with factory calibration (rgb intrinsic and rgb/ir registration) has a huge reprojection error.Wed, 11 Dec 2013 03:50:51 -0600http://answers.opencv.org/question/25030/solvepnp-not-giving-identity/?comment=25284#post-id-25284Comment by berak for <p>Hi,</p>
<p>I'm trying to understand how solvePnP really works. I use a kinect camera to get SIFT keypoints and the corresponding 3D points.
I give the 2D/3D couples to solvePnP and I expect it to give me the identity matrix as this is equivalent to stare at the same scene without moving. </p>
<p>Result : though the rotation part is the identity, I get a strange translation vector : [0.05, 0.1, 0.8]. These values seem too large, and I can't understand why the Z part is so big compared to the others.</p>
<p>Overall the result is wrong as I get a huge translation along Z.</p>
<p>Any idea as to why this happens ?</p>
http://answers.opencv.org/question/25030/solvepnp-not-giving-identity/?comment=25032#post-id-25032example code ? mock data ? please help us help you.Thu, 05 Dec 2013 08:59:26 -0600http://answers.opencv.org/question/25030/solvepnp-not-giving-identity/?comment=25032#post-id-25032