calc_Q_from_P

% calculates projection matrix Q for lines from P
 see PCV (12.71)

 Usage:
   Q = calc_Q_from_P (P)
  
   P - 4 x 3-projection matrix P = K*R*[I|-Z] 
   Q - 3x6 projection matrix for lines

 Wolfgang Förstner
 wfoerstn@uni-bonn.de 

 See also calc_P_from_KRZ, calc_KRZ_from_P, calc_viewing_direction

0001 %% calculates projection matrix Q for lines from P
0002 % see PCV (12.71)
0003 %
0004 % Usage:
0005 %   Q = calc_Q_from_P (P)
0006 %
0007 %   P - 4 x 3-projection matrix P = K*R*[I|-Z]
0008 %   Q - 3x6 projection matrix for lines
0009 %
0010 % Wolfgang Förstner
0011 % wfoerstn@uni-bonn.de
0012 %
0013 % See also calc_P_from_KRZ, calc_KRZ_from_P, calc_viewing_direction
0014 
0015 function Q = calc_Q_from_P (P)
0016 
0017 A=P(1,:)';
0018 B=P(2,:)';
0019 C=P(3,:)';
0020 
0021 Q=[(calc_Pi(B) * C)'; ...
0022    (calc_Pi(C) * A)'; ...
0023    (calc_Pi(A) * B)'];