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Improved documentation of inertia and slightly changed the interface (added a constructor)

This commit is contained in:
Paolo Cignoni 2012-10-16 07:36:35 +00:00
parent bebfa3eb8b
commit ac9b6b16f2
1 changed files with 45 additions and 23 deletions
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56
vcg/complex/algorithms/inertia.h
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@ -23,7 +23,18 @@
#ifndef _VCG_INERTIA_
#define _VCG_INERTIA_
/*
#include <eigenlib/Eigen/Core>
#include <eigenlib/Eigen/Eigenvalues>
#include <vcg/complex/algorithms/update/normal.h>
namespace vcg
{
namespace tri
{
/*! \brief Methods for computing Polyhedral Mass properties (like inertia tensor, volume, etc)
The algorithm is based on a three step reduction of the volume integrals
to successively simpler integrals. The algorithm is designed to minimize
the numerical errors that can result from poorly conditioned alignment of
@ -34,24 +45,14 @@ floating point operations.
For more information, check out:
Brian Mirtich,
<b>Brian Mirtich,</b>
``Fast and Accurate Computation of Polyhedral Mass Properties,''
journal of graphics tools, volume 1, number 2, 1996
*/
#include <eigenlib/Eigen/Core>
#include <eigenlib/Eigen/Eigenvalues>
#include <vcg/complex/algorithms/update/normal.h>
namespace vcg
{
namespace tri
{
template <class InertiaMeshType>
template <class MeshType>
class Inertia
{
typedef InertiaMeshType MeshType;
typedef typename MeshType::VertexType VertexType;
typedef typename MeshType::VertexPointer VertexPointer;
typedef typename MeshType::VertexIterator VertexIterator;
@ -82,6 +83,12 @@ private :
double T0, T1[3], T2[3], TP[3];
public:
/*! \brief Basic constructor
When you create a Inertia object, you have to specify the mesh that it refers to.
The properties are computed at that moment. Subsequent modification of the mesh does not affect these values.
*/
Inertia(MeshType &m) {Compute(m);}
/* compute various integrations over projection of face */
void compProjectionIntegrals(FaceType &f)
@ -176,6 +183,11 @@ void CompFaceIntegrals(FaceType &f)
}
/*! main function to be called.
It requires a watertight mesh with per face normals.
*/
void Compute(MeshType &m)
{
tri::UpdateNormal<MeshType>::PerFaceNormalized(m);
@ -216,11 +228,19 @@ void Compute(MeshType &m)
TP[X] /= 2; TP[Y] /= 2; TP[Z] /= 2;
}
/*! \brief Return the Volume (or mass) of the mesh.
Meaningful only if the mesh is watertight.
*/
ScalarType Mass()
{
return static_cast<ScalarType>(T0);
}
/*! \brief Return the Center of Mass (or barycenter) of the mesh.
Meaningful only if the mesh is watertight.
*/
Point3<ScalarType> CenterOfMass()
{
Point3<ScalarType> r;
@ -275,8 +295,10 @@ void InertiaTensor(Eigen::Matrix3d &J )
}
/** Compute eigenvalues and eigenvectors of inertia tensor.
The eigenvectors make a rotation matrix that aligns the mesh along the axes of min/max inertia
/*! \brief Return the Inertia tensor the mesh.
The result is factored as eigenvalues and eigenvectors (as ROWS).
*/
void InertiaTensorEigen(Matrix33<ScalarType> &EV, Point3<ScalarType> &ev )
{
@ -284,9 +306,9 @@ void InertiaTensorEigen(Matrix33<ScalarType> &EV, Point3<ScalarType> &ev )
InertiaTensor(it);
Eigen::SelfAdjointEigenSolver<Eigen::Matrix3d> eig(it);
Eigen::Vector3d c_val = eig.eigenvalues();
Eigen::Matrix3d c_vec = eig.eigenvectors();
Eigen::Matrix3d c_vec = eig.eigenvectors(); // eigenvector are stored as columns.
EV.FromEigenMatrix(c_vec);
EV.transposeInPlace();
ev.FromEigenVector(c_val);
}