overlaps_alignedbox_sphere.h

// Description: Overlap tests between an aligned box and a sphere

#ifndef PASTELGEOMETRY_OVERLAPS_ALIGNEDBOX_SPHERE_H
#define PASTELGEOMETRY_OVERLAPS_ALIGNEDBOX_SPHERE_H

#include "pastel/geometry/shape/alignedbox.h"
#include "pastel/geometry/shape/sphere.h"
#include "pastel/geometry/distance/distance_alignedbox_sphere.h"

#include "pastel/sys/math_functions.h"

namespace Pastel
{

    //! Tests if an aligned box and a sphere overlap.
    /*!
   Preconditions:
   alignedBox.n() == sphere.n()

   Time complexity:
   O(n), where n is the dimension.

   Returns:
   Whether the box and the sphere overlap.

   Note: Currently the box is assumed closed.
   */
    template <typename Real, int N>
    bool overlaps(
        const AlignedBox<Real, N>& alignedBox,
        const Sphere<Real, N>& sphere)
    {
        // An aligned box and a sphere intersect if
        // the distance of the sphere's center
        // point from the aligned box is smaller
        // than the sphere's radius.

        // FIX: The box's topology is not handled correctly.
        // I do not see a way to handle it.
        // The box is assumed closed.

        Real d2 =
            distance2(alignedBox, sphere.position());
        Real radius2 =
            square(sphere.radius());

        if (d2 >= radius2)
        {
            if (d2 > radius2 ||
                sphere.topology() == Topology::Open)
            {
                return false;
            }
        }

        return true;
    }

}

#endif