Math about the 2 point perspective


Hi all,

Here is my problem: I have an aerial images, and I have calculated the position and orientation of the camera and can successfully load the image as background to matchphoto by the Ruby API.

For a 3D projection, the basic math for a point P(X, Y, Z, 1) projected to a image point m(x,y,1) is

m = K(R,t)P

and I can turn this formula to the (eye target up aspect_ratio focal length and fov) that are need to create a camera used by the matchphoto.

However, what confused me is the center_2d and scale_2d parameter of the camera when I pan and zoom the matchphoto scene.

My question is what is the mathematical significances of the two parameters for the 2 point perspective camera for the matchphoto? How can they tell how much I have panned or zoomed of the scene?