Hi.

My name is Rodrigo Minetto and I'm a student of computer science. I'm
interested in your work
ARToolkit.

I have a trouble of a conversion between your camera calibration
structure, the 3x4 matrix that results from arGetTransMat, to a
calibration
matrix returned by the Tsai camera calibration algorithm.

One big problem is: How to use the focal distance of your
camera_para.dat to compute the undistorted coordinates (or camera
screen coordinates).

In particular the functions of the Tsai paper:

* Camera coordinates to undistorted sensor coordinates (pf-->pu): :

p_u_x = focal_distance * x_c / z_c;
p_u_y = focal_distance * y_c / z_c;

* Undistorted sensor coordinates to distorted sensor coordinates (pu-- 
 >pd):

Solution of a cubic.

* Distorted sensor coordinates to undistorted sensor coordinates (pd-- 
 >pu):

distortion_factor = 1 + kappa * (p_d_x *p_d_x  + p_d_y *p_d_y );
p_u_x = p_d_x * distortion_factor;
p_u_y = p_d_y * distortion_factor;

* Sensor coordinates to image coordinates (pd-->pi):

p_i_x = image_center_in_x + sx * (p_d_x/dpx);
p_i_y = image_center_in_y + p_d_y/dpy;

where dpx and dpx are the size of the sensors elements in the camera
and sx is a scale factor.

* Image coordinates to sensor coordinates (pi-->pd):

p_d_x = dpx * (p_i_x - image_center_in_x ) / sx;
p_d_y = dpy * (p_i_y - image_center_in_y);

Thank you very much.
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