[Insight-users] how to calculate line from a point

[milentie at arcor.de]

Hi all users,

i want to make camera calibration, where the intrinsic camera parameters are known and I have only 4 3D - 2D corresponding points. 
So I want to user plücker coordinates and dual quaternions for computin the rotation and the translation of the camera. My question is, how I can compute a line and line directin from the 2D and the 3D points?
I was doing like this for the image points:

p1 = inverse(M) * Ximg,  where M are the intrinsic camera parameters than a took another point from this line
p2 = p1/ 2 and the I compute the line direction like:  Line_direction = p2 - p1
and the line momemt Lm = p1xLine_direction

and for the 3D point 
w1 = M * Xworld;
w2 = w1 / 2;
Line_direction = w2 - w1;
Line_moment = w1 x Line_direction;

Is this correct?
Can I construct the Line_directin and the line moment for the 2D and the 3D point 
and then to build the dual quaternions

Thanks
dime



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