RigidBodyInertia.h

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//
// Copyright (c) 2009, Markus Rickert
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#ifndef RL_MATH_RIGIDBODYINERTIA_H
#define RL_MATH_RIGIDBODYINERTIA_H
 
#include <Eigen/Core>
 
namespace rl
{
    namespace math
    {
        namespace spatial
        {
            template<typename Scalar> class ForceVector;
            
            template<typename Scalar> class MotionVector;
            
            template<typename Scalar>
            class RigidBodyInertia
            {
            public:
                EIGEN_MAKE_ALIGNED_OPERATOR_NEW
                
                typedef Scalar ScalarType;
                
                typedef ::Eigen::Matrix<Scalar, 6, 6> MatrixType;
                
                typedef ::Eigen::Matrix<Scalar, 3, 1> CenterOfGravityType;
                
                typedef const CenterOfGravityType ConstCenterOfGravityType;
                
                typedef ::Eigen::Matrix<Scalar, 3, 3> InertiaType;
                
                typedef const InertiaType ConstInertiaType;
                
                typedef Scalar MassType;
                
                typedef const MassType ConstMassType;
                
                RigidBodyInertia()
                {
                }
                
                template<typename OtherDerived>
                RigidBodyInertia(const ::Eigen::DenseBase<OtherDerived>& other) :
                    centerOfGravityData(other.template topRightCorner<3, 3>().cross3()),
                    inertiaData(other.template topLeftCorner<3, 3>()),
                    massData(other.template bottomRightCorner<3, 3>().diagonal().mean())
                {
                }
                
                virtual ~RigidBodyInertia()
                {
                }
                
                CenterOfGravityType& cog()
                {
                    return centerOfGravityData;
                }
                
                ConstCenterOfGravityType& cog() const
                {
                    return centerOfGravityData;
                }
                
                InertiaType& inertia()
                {
                    return inertiaData;
                }
                
                ConstInertiaType& inertia() const
                {
                    return inertiaData;
                }
                
                MassType& mass()
                {
                    return massData;
                }
                
                ConstMassType& mass() const
                {
                    return massData;
                }
                
                MatrixType matrix() const
                {
                    MatrixType res;
                    res.template topLeftCorner<3, 3>() = inertia();
                    res.template topRightCorner<3, 3>() = cog().cross33();
                    res.template bottomLeftCorner<3, 3>() = -cog().cross33();
                    res.template bottomRightCorner<3, 3>() = ::Eigen::Matrix<Scalar, 3, 3>::Identity() * mass();
                    return res;
                }
                
                template<typename OtherDerived>
                RigidBodyInertia& operator=(const ::Eigen::MatrixBase<OtherDerived>& other)
                {
                    cog() = other.template topRightCorner<3, 3>().cross3();
                    inertia() = other.template topLeftCorner<3, 3>();
                    mass() = other.template bottomRightCorner<3, 3>().diagonal().mean();
                    return *this;
                }
                
                RigidBodyInertia operator+(const RigidBodyInertia& other) const
                {
                    RigidBodyInertia res;
                    res.cog() = cog() + other.cog();
                    res.inertia() = inertia() + other.inertia();
                    res.mass() = mass() + other.mass();
                    return res;
                }
                
                RigidBodyInertia operator-(const RigidBodyInertia& other) const
                {
                    RigidBodyInertia res;
                    res.cog() = cog() - other.cog();
                    res.inertia() = inertia() - other.inertia();
                    res.mass() = mass() - other.mass();
                    return res;
                }
                
                template<typename OtherScalar>
                RigidBodyInertia operator*(const OtherScalar& other) const
                {
                    RigidBodyInertia res;
                    res.cog() = cog() * other;
                    res.inertia() = inertia() * other;
                    res.mass() = mass() * other;
                    return res;
                }
                
                template<typename OtherScalar>
                ForceVector<Scalar> operator*(const MotionVector<OtherScalar>& other) const;
                
                template<typename OtherScalar>
                RigidBodyInertia operator/(const OtherScalar& other) const
                {
                    RigidBodyInertia res;
                    res.cog() = cog() / other;
                    res.inertia() = inertia() / other;
                    res.mass() = mass() / other;
                    return res;
                }
                
                void setIdentity()
                {
                    cog().setZero();
                    inertia().setIdentity();
                    mass() = 1;
                }
                
                void setZero()
                {
                    cog().setZero();
                    inertia().setZero();
                    mass() = 0;
                }
                
            protected:
                
            private:
                CenterOfGravityType centerOfGravityData;
                
                InertiaType inertiaData;
                
                MassType massData;
            };
        }
    }
}
 
#endif // RL_MATH_RIGIDBODYINERTIA_H