Blender  V3.3
nviewtriangulation.h
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1 // Copyright (c) 2009 libmv authors.
2 //
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4 // of this software and associated documentation files (the "Software"), to
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7 // sell copies of the Software, and to permit persons to whom the Software is
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9 //
10 // The above copyright notice and this permission notice shall be included in
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13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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15 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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19 // IN THE SOFTWARE.
20 //
21 // Compute a 3D position of a point from several images of it. In particular,
22 // compute the projective point X in R^4 such that x = PX.
23 //
24 // Algorithm is the standard DLT; for derivation see appendix of Keir's thesis.
25 
26 #ifndef LIBMV_MULTIVIEW_NVIEWTRIANGULATION_H
27 #define LIBMV_MULTIVIEW_NVIEWTRIANGULATION_H
28 
29 #include "libmv/base/vector.h"
30 #include "libmv/logging/logging.h"
31 #include "libmv/numeric/numeric.h"
32 
33 namespace libmv {
34 
35 // x's are 2D coordinates (x,y,1) in each image; Ps are projective cameras. The
36 // output, X, is a homogeneous four vectors.
37 template <typename T>
38 void NViewTriangulate(const Matrix<T, 2, Dynamic>& x,
39  const vector<Matrix<T, 3, 4>>& Ps,
40  Matrix<T, 4, 1>* X) {
41  int nviews = x.cols();
42  assert(nviews == Ps.size());
43 
44  Matrix<T, Dynamic, Dynamic> design(3 * nviews, 4 + nviews);
45  design.setConstant(0.0);
46  for (int i = 0; i < nviews; i++) {
47  design.template block<3, 4>(3 * i, 0) = -Ps[i];
48  design(3 * i + 0, 4 + i) = x(0, i);
49  design(3 * i + 1, 4 + i) = x(1, i);
50  design(3 * i + 2, 4 + i) = 1.0;
51  }
52  Matrix<T, Dynamic, 1> X_and_alphas;
53  Nullspace(&design, &X_and_alphas);
54  X->resize(4);
55  *X = X_and_alphas.head(4);
56 }
57 
58 // x's are 2D coordinates (x,y,1) in each image; Ps are projective cameras. The
59 // output, X, is a homogeneous four vectors.
60 // This method uses the algebraic distance approximation.
61 // Note that this method works better when the 2D points are normalized
62 // with an isotopic normalization.
63 template <typename T>
64 void NViewTriangulateAlgebraic(const Matrix<T, 2, Dynamic>& x,
65  const vector<Matrix<T, 3, 4>>& Ps,
66  Matrix<T, 4, 1>* X) {
67  int nviews = x.cols();
68  assert(nviews == Ps.size());
69 
70  Matrix<T, Dynamic, 4> design(2 * nviews, 4);
71  for (int i = 0; i < nviews; i++) {
72  design.template block<2, 4>(2 * i, 0) = SkewMatMinimal(x.col(i)) * Ps[i];
73  }
74  X->resize(4);
75  Nullspace(&design, X);
76 }
77 
78 } // namespace libmv
79 
80 #endif // LIBMV_MULTIVIEW_RESECTION_H
#define X
Definition: GeomUtils.cpp:199
void NViewTriangulateAlgebraic(const Matrix< T, 2, Dynamic > &x, const vector< Matrix< T, 3, 4 >> &Ps, Matrix< T, 4, 1 > *X)
double Nullspace(TMat *A, TVec *nullspace)
Definition: numeric.h:158
Mat23 SkewMatMinimal(const Vec2 &x)
Definition: numeric.h:475
void NViewTriangulate(const Matrix< T, 2, Dynamic > &x, const vector< Matrix< T, 3, 4 >> &Ps, Matrix< T, 4, 1 > *X)