1 #include "btPolarDecomposition.h"
6 btScalar abs_column_sum(const btMatrix3x3& a, int i)
8 return btFabs(a[0][i]) + btFabs(a[1][i]) + btFabs(a[2][i]);
11 btScalar abs_row_sum(const btMatrix3x3& a, int i)
13 return btFabs(a[i][0]) + btFabs(a[i][1]) + btFabs(a[i][2]);
16 btScalar p1_norm(const btMatrix3x3& a)
18 const btScalar sum0 = abs_column_sum(a, 0);
19 const btScalar sum1 = abs_column_sum(a, 1);
20 const btScalar sum2 = abs_column_sum(a, 2);
21 return btMax(btMax(sum0, sum1), sum2);
24 btScalar pinf_norm(const btMatrix3x3& a)
26 const btScalar sum0 = abs_row_sum(a, 0);
27 const btScalar sum1 = abs_row_sum(a, 1);
28 const btScalar sum2 = abs_row_sum(a, 2);
29 return btMax(btMax(sum0, sum1), sum2);
33 btPolarDecomposition::btPolarDecomposition(btScalar tolerance, unsigned int maxIterations)
34 : m_tolerance(tolerance), m_maxIterations(maxIterations)
38 unsigned int btPolarDecomposition::decompose(const btMatrix3x3& a, btMatrix3x3& u, btMatrix3x3& h) const
40 // Use the 'u' and 'h' matrices for intermediate calculations
44 for (unsigned int i = 0; i < m_maxIterations; ++i)
46 const btScalar h_1 = p1_norm(h);
47 const btScalar h_inf = pinf_norm(h);
48 const btScalar u_1 = p1_norm(u);
49 const btScalar u_inf = pinf_norm(u);
51 const btScalar h_norm = h_1 * h_inf;
52 const btScalar u_norm = u_1 * u_inf;
54 // The matrix is effectively singular so we cannot invert it
55 if (btFuzzyZero(h_norm) || btFuzzyZero(u_norm))
58 const btScalar gamma = btPow(h_norm / u_norm, 0.25f);
59 const btScalar inv_gamma = btScalar(1.0) / gamma;
61 // Determine the delta to 'u'
62 const btMatrix3x3 delta = (u * (gamma - btScalar(2.0)) + h.transpose() * inv_gamma) * btScalar(0.5);
64 // Update the matrices
68 // Check for convergence
69 if (p1_norm(delta) <= m_tolerance * u_1)
71 h = u.transpose() * a;
72 h = (h + h.transpose()) * 0.5;
77 // The algorithm has failed to converge to the specified tolerance, but we
78 // want to make sure that the matrices returned are in the right form.
79 h = u.transpose() * a;
80 h = (h + h.transpose()) * 0.5;
82 return m_maxIterations;
85 unsigned int btPolarDecomposition::maxIterations() const
87 return m_maxIterations;
90 unsigned int polarDecompose(const btMatrix3x3& a, btMatrix3x3& u, btMatrix3x3& h)
92 static btPolarDecomposition polar;
93 return polar.decompose(a, u, h);