72 lines
1.2 KiB
C++
72 lines
1.2 KiB
C++
#pragma once
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#include <cgv/math/mat.h>
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#include <cgv/math/inv.h>
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#include <cgv/math/constants.h>
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#include <limits>
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#include <algorithm>
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namespace cgv {
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namespace math {
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///polar decomposition of matrix c=r*a
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///r orthonormal matrix
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///a positive semi-definite matrix
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template <typename T>
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void polar(const mat<T> &c, mat<T> &r, mat<T> &a,int num_iter=15)
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{
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r = c;
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for(int i =0; i < num_iter;i++)
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r = ((T)0.5)*(r+transpose(inv(r)));
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a = inv(r)*c;
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/*
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* Alternative way using svd:
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* c = u*d*v^t
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* r = u*v^t, a=v*d*v^t
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*/
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}
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/// extract axis and angle from rotation matrix
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///returns true if successful problematic cases are angle == 0° and angle == 180°
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template <typename T>
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bool decompose_rotation(const cgv::math::mat<T>& R,
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cgv::math::vec<T>& axis,
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T& angle)
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{
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assert(R.nrows() == 3 && R.ncols() == 3);
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mat<T> A = (T)0.5*(R - transpose(R));
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mat<T> S = (T)0.5*(R + transpose(R));
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T abssina = (T)sqrt(0.5*(double)(A.frobenius_norm()*A.frobenius_norm()));
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T cosa = 0.5*(trace(S)-1.0);
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angle =(T)(asin(abssina)*180.0/PI);
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if(cosa < 0)
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angle = (T)180.0-angle;
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if(angle == 0 || angle == 180.0)
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return false;
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axis = (T)1.0/abssina*cgv::math::vec<T>(A(2,1),A(0,2),A(1,0));
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return true;
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}
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}
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}
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