PointCylinderNearest.h

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/*  Copyright (C) 2003-2021 Free Electron Organization
    Any use of this software requires a license.  If a valid license
    was not distributed with this file, visit freeelectron.org. */

/** @file */

#ifndef __geometry_PointCylinderNearest_h__
#define __geometry_PointCylinderNearest_h__

namespace fe
{
namespace ext
{

/**************************************************************************//**
    @brief Find point nearest to a cylindrical solid

    @ingroup geometry
*//***************************************************************************/
template <typename T>
class PointCylinderNearest
{
    public:
static  T   solve(const Vector<3,T>& base,const Vector<3,T>& axis,
                    const T radius,const Vector<3,T>& origin,
                    Vector<3,T>& direction,T& along,Vector<3,T>& intersection);
};

template <typename T>
inline T PointCylinderNearest<T>::solve(
        const Vector<3,T>& base,const Vector<3,T>& axis,const T radius,
        const Vector<3,T>& origin, Vector<3,T>& direction,
        T& along,Vector<3,T>& intersection)
{
    const T length=magnitude(axis);
    const Vector<3,T> unitAxis=axis*(length>T(0)? T(1)/length: T(1));
    const Vector<3,T> towards=origin-base;
    along=dot(towards,unitAxis);

#if FALSE
    feLog("\nbase %s axis %s radius %.6G\n",
            c_print(base),c_print(axis),radius);
    feLog("origin: %s\n",c_print(origin));

    feLog("along: %.6G/%.6G\n",along,length);
#endif

    Vector<3,T> center=base+along*unitAxis;
    Vector<3,T> radial=origin-center;
    const T radial_mag=magnitude(radial);
    if(radial_mag>T(0))
    {
        radial*=radius/radial_mag;
    }
    if(along<T(0))
    {
        along=T(0);
        center=base;
    }
    else if(along>length)
    {
        along=length;
        center=base+axis;
    }

    intersection=center+radial;
    direction=intersection-origin;
    T mag=magnitude(direction);
    if(mag>T(0))
    {
        direction*=T(1)/mag;
    }

#if FALSE
    feLog("intersection: %s\n",c_print(intersection));
    feLog("direction: %s\n",c_print(direction));
#endif

    return mag;
}

} /* namespace ext */
} /* namespace fe */

#endif /* __geometry_PointCylinderNearest_h__ */