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Make PCA of iso cuboid more conform to paper formulas

This commit is contained in:
Simon Giraudot 2020-10-29 09:24:36 +01:00
parent 77b2c1ecc4
commit 913c29bbca
1 changed files with 18 additions and 11 deletions
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29
Principal_component_analysis/include/CGAL/PCA_util_Eigen.h
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@ -149,18 +149,25 @@ assemble_covariance_matrix_3(InputIterator first,
// defined for convenience.
// FT example = CGAL::to_double(t[0].x());
FT x0 = t[0].x();
FT y0 = t[0].y();
FT z0 = t[0].z();
FT delta[9] = {t[1].x()-x0, t[3].x()-x0, t[5].x()-x0,
t[1].y()-y0, t[3].y()-y0, t[5].y()-y0,
t[1].z()-z0, t[3].z()-z0, t[5].z()-z0};
Matrix transformation (delta);
FT volume = t.volume();
FT x0 = t.xmin();
FT y0 = t.ymin();
FT z0 = t.zmin();
FT x1 = t.xmax();
FT y1 = t.ymax();
FT z1 = t.zmax();
Matrix transformation;
transformation << x1 - x0, 0 , 0 ,
0 , y1 - y0, 0 ,
0 , 0 , z1 - z0;
FT volume = (x1-x0) * (y1-y0) * (z1-z0);
// skip zero measure primitives
if(volume == (FT)0.0)
continue;
CGAL_assertion(volume > 0.0);
// Find the 2nd order moment for the cuboid wrt to the origin by an affine transformation.
@ -168,9 +175,9 @@ assemble_covariance_matrix_3(InputIterator first,
transformation = volume * transformation * moment * transformation.transpose();
// Translate the 2nd order moment to the minimum corner (x0,y0,z0) of the cuboid.
FT xav0 = (delta[0] + delta[1] + delta[2])/4.0;
FT yav0 = (delta[3] + delta[4] + delta[5])/4.0;
FT zav0 = (delta[6] + delta[7] + delta[8])/4.0;
FT xav0 = (x1 - x0) / (4.0);
FT yav0 = (y1 - y0) / (4.0);
FT zav0 = (z1 - z0) / (4.0);
// and add to covariance matrix
covariance[0] += transformation(0,0) + volume * (2*x0*xav0 + x0*x0);