distance_alignedbox_sphere.hpp

#ifndef PASTELGEOMETRY_DISTANCE_ALIGNEDBOX_SPHERE_HPP
#define PASTELGEOMETRY_DISTANCE_ALIGNEDBOX_SPHERE_HPP

#include "pastel/geometry/distance/distance_alignedbox_sphere.h"
#include "pastel/geometry/distance/distance_alignedbox_point.h"

namespace Pastel
{

    template <typename Real, integer N>
    Real distance(
        const AlignedBox<Real, N>& box,
        const Sphere<Real, N>& sphere)
    {
        PENSURE_OP(box.n(), ==, sphere.n());

        // Let
        // s = distance from sphere's center to 'box'.
        // r = sphere's radius
        // Then the distance d is given by
        // d = s - r
        // Negative distance means overlapping,
        // so then zero distance is returned.
        // d < 0 <=> s - r < 0 <=> s < r <=> s^2 < r^2

        Real centerDistance2 =
            distance2(box, sphere.position());

        if (centerDistance2 <= square(sphere.radius()))
        {
            return 0;
        }

        return std::sqrt(centerDistance2) - sphere.radius();
    }

    template <typename Real, integer N>
    Real distance2(
        const AlignedBox<Real, N>& box,
        const Sphere<Real, N>& sphere)
    {
        PENSURE_OP(box.n(), ==, sphere.n());

        return square(Pastel::distance(box, sphere));
    }

}

#endif