function [A,avgres] = dltfu(F,L,Cut)
% Description: Program to calculate DLT coefficient for one camera
% Note that at least 6 (valid) calibration points are needed
% function [A,avgres] = dltfu(F,L,Cut)
% Input: - F matrix containing the global coordinates (X,Y,Z)
% of the calibration frame
% e.g.: [0 0 20;0 0 50;0 0 100;0 60 20 ...]
% - L matrix containing 2d coordinates of calibration
% points seen in camera (same sequence as in F)
% e.g.: [1200 1040; 1200 1360; ...]
% - Cut points that are not visible in camera;
% not being used to calculate DLT coefficient
% e.g.: [1 7] -> calibration point 1 and 7
% will be discarded.
% This input is optional (default Cut=[])
% Output: - A 11 DLT coefficients
% - avgres average residuals (measure for fit of dlt)
% given in units of camera coordinates
%
% Author: Christoph Reinschmidt, HPL, The University of Calgary
% Date: January, 1994
% Last changes: November 29, 1996
% Version: 1.0
% References: Woltring and Huiskes (1990) Stereophotogrammetry. In
% Biomechanics of Human Movement (Edited by Berme and
% Cappozzo). pp. 108-127.
%License
% Copyright (C) 1994 Reinschmidt
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see .
if nargin==2; Cut=[]; end;
if size(F,1) ~= size(L,1)
disp('# of calibration points entered and seen in camera do not agree'), return
end
m=size(F,1); Lt=L'; C=Lt(:);
for i=1:m
B(2*i-1,1) = F(i,1);
B(2*i-1,2) = F(i,2);
B(2*i-1,3) = F(i,3);
B(2*i-1,4) = 1;
B(2*i-1,9) =-F(i,1)*L(i,1);
B(2*i-1,10) =-F(i,2)*L(i,1);
B(2*i-1,11) =-F(i,3)*L(i,1);
B(2*i,5) = F(i,1);
B(2*i,6) = F(i,2);
B(2*i,7) = F(i,3);
B(2*i,8) = 1;
B(2*i,9) =-F(i,1)*L(i,2);
B(2*i,10) =-F(i,2)*L(i,2);
B(2*i,11) =-F(i,3)*L(i,2);
end
% Cut the lines out of B and C including the control points to be discarded
Cutlines=[Cut.*2-1, Cut.*2];
B([Cutlines],:)=[];
C([Cutlines],:)=[];
% Solution for the coefficients
A=B\C;
D=B*A;
R=C-D;
res=norm(R); avgres=res/size(R,1)^0.5;