sugr_generate_true_2D_point_pairs_homography

% Generate 2D point pairs from homography,
 i.e., for given H generate N point pairs

 PP = sugr_generate_true_2D_point_pairs_homography(H,N,boolean_r);

 H = 3x3 matrix
 N = number of points (in square [-1,1]^2
 boolean_r = boolean: points should sit random
                else: points sit in a square (N should be square)

 PP = point pairs
      PP.h = N x 6 matrix of pairs of homogeneous point coordinates
      PP.Crr = N x 4 x 4 sith 4 x4 CovM of point pairs
      PP.type = 8 * ones(N,1)

 Wolfgang Förstner
 wfoerstn@uni-bonn.de

 wf 02/2011

0001 %% Generate 2D point pairs from homography,
0002 % i.e., for given H generate N point pairs
0003 %
0004 % PP = sugr_generate_true_2D_point_pairs_homography(H,N,boolean_r);
0005 %
0006 % H = 3x3 matrix
0007 % N = number of points (in square [-1,1]^2
0008 % boolean_r = boolean: points should sit random
0009 %                else: points sit in a square (N should be square)
0010 %
0011 % PP = point pairs
0012 %      PP.h = N x 6 matrix of pairs of homogeneous point coordinates
0013 %      PP.Crr = N x 4 x 4 sith 4 x4 CovM of point pairs
0014 %      PP.type = 8 * ones(N,1)
0015 %
0016 % Wolfgang Förstner
0017 % wfoerstn@uni-bonn.de
0018 %
0019 % wf 02/2011
0020 
0021 function PP = sugr_generate_true_2D_point_pairs_homography(H,N,br)
0022 
0023 if br
0024     for n=1:N
0025         x             = [rand(2,1)*2-1;1];
0026         y             = H * x;
0027         PP.h(n,:)     = [x',y'];
0028         PP.Crr(n,:,:) = zeros(4);
0029         PP.type(n)    = 8;
0030     end
0031 else
0032     M = ceil(sqrt(N));
0033     n=0;
0034     for m=1:M
0035         for k=1:M
0036             n = n+1;
0037             if n <= N
0038                 x = [-(M-1)/2+2*(m-1)/(M-1);-(M-1)/2+2*(k-1)/(M-1);1];
0039                 y             = H * x;
0040                 PP.h(n,:)     = [x',y'];
0041                 PP.Crr(n,:,:) = zeros(4);
0042                 PP.type(n)    = 8;
0043             end
0044         end
0045     end
0046 end