Last change
on this file since 177 was
37,
checked in by (none), 15 years ago
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Added original make3d
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Property svn:executable set to
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File size:
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1 | %vgg_X_from_xP_lin Estimation of 3D point from image matches and camera matrices, linear.
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2 | % X = vgg_X_from_xP_lin(x,P,imsize) computes projective 3D point X (column 4-vector)
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3 | % from its projections in K images x (3-by-K matrix) and camera matrices P (K-cell
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4 | % of 3-by-4 matrices). Image sizes imsize (2-by-K matrix) are needed for preconditioning.
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5 | % By minimizing algebraic distance.
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6 | %
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7 | % See also vgg_X_from_xP_nonlin.
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8 |
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9 | % werner@robots.ox.ac.uk, 2003
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10 |
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11 | function X = vgg_X_from_xP_lin(u,P,imsize)
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12 |
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13 | if iscell(P)
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14 | P = cat(3,P{:});
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15 | end
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16 | K = size(P,3);
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17 |
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18 | if nargin>2
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19 | for k = 1:K
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20 | H = [2/imsize(1,k) 0 -1
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21 | 0 2/imsize(2,k) -1
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22 | 0 0 1];
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23 | P(:,:,k) = H*P(:,:,k);
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24 | u(:,k) = H(1:2,1:2)*u(:,k) + H(1:2,3);
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25 | end
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26 | end
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27 |
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28 | A = [];
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29 | for k = 1:K
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30 | A = [A; vgg_contreps([u(:,k);1])*P(:,:,k)];
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31 | end
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32 | % A = normx(A')';
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33 | [dummy,dummy,X] = svd(A,0);
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34 | X = X(:,end);
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35 |
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36 | % Get orientation right
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37 | s = reshape(P(3,:,:),[4 K])'*X;
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38 | if any(s<0)
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39 | X = -X;
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40 | if any(s>0)
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41 | % warning('Inconsistent orientation of point match');
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42 | end
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43 | end
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44 |
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45 | return
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