Out-of-plane rotation vs In plane rotation Recently I have been reading a lot of papers about Computer Vison, more specifically trackers. There are various criteria taken into consideration to evaluate the robustness of a tracker; like how well it can handle illumination variation, occlusion, fast motion etc. I understand pretty much all of the parameters except the two mentioned in the title. Could some explain me the each of them, and their differences?
Thank you.
In-Plane Rotation - the target rotates in the image plane.
Out-of-Plane  Rotation  -  the  target  rotates  out  of  the  image plane.1
[1]Y. Wu, J. Lim, and M.-H. Yang, “Online object tracking: A benchmark,” in CVPR, 2013

In Plane Rotation: Suppose you have a camera that is looking on an object and imagine a vector starting from the center of the camera lens and going to the object. Now if you simply spin your camera along that vector this is called in plane rotation (the plane of your camera lens does not change but it has rotated in this plane). The image of the object after this rotation only shows that object has rotated nothing else changes.
Out of plane rotation: any other rotation where the new position of the camera lens is not in its last plane.
