quaternion_helper.h

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#ifndef IMU_FILTER_QUATERNION_HELPER_H
#define IMU_FILTER_QUATERNION_HELPER_H

#include <Eigen/Geometry>

#include <imu_filter/utils.h>

namespace imu_filter 
{
        //* Helper functions for quaternions
        namespace quaternion_helper
        {
                static inline void fromPerturbation( Eigen::Quaterniond & q, const Eigen::Vector3d & omega )
                {
                        q.w() = 1.0;
                        q.x() = 0.5 * omega.x();
                        q.y() = 0.5 * omega.y();
                        q.z() = 0.5 * omega.z();
                }

                static inline void recalcWForNormalizedQ( Eigen::Quaterniond & q )
                {
                        double sqr = utils::square( q.x() ) + utils::square( q.y() ) + utils::square( q.z() );

                        if( sqr > 0.9999 ){
                                q.coeffs() = -q.coeffs();
                                sqr += 0.01;
                                q.coeffs() /= sqr;
                                sqr = utils::square( q.x() ) + utils::square( q.y() ) + utils::square( q.z() );
                        }
                        q.w() = sqrt( 1.0 - sqr );
                }
        }
}

#endif