overlaps_alignedplane_box.h

// Description: Overlap tests between an aligned plane an a box

#ifndef PASTELGEOMETRY_OVERLAPS_ALIGNEDPLANE_BOX_H
#define PASTELGEOMETRY_OVERLAPS_ALIGNEDPLANE_BOX_H

#include "pastel/geometry/shape/alignedplane.h"
#include "pastel/geometry/shape/box.h"
#include "pastel/sys/mytypes.h"

namespace Pastel
{

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

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

   Note: Currently the box is assumed to be closed.
   */
    template <typename Real, int N>
    bool overlaps(
        const AlignedPlane<Real, N>& plane,
        const Box<Real, N>& box)
    {
        PENSURE_OP(plane.n(), ==, box.n());

        // FIX: The topology of the box is not
        // handled correctly. The box is assumed
        // to be closed.

        // Compute the radius of the projection
        // of the box onto the plane normal.

        Real radius = 0;

        integer n = plane.n();
        for (integer i = 0;i < n;++i)
        {
            // Move on the edges of the box
            // so that the positive axis direction
            // is always chosen.
            // When finished, we will be in the point
            // where the box's surface is farthest from
            // its origin. Because the box is symmetric
            // w.r.t its axes, the minimal point
            // is also found in -radius.

            radius += abs(box.rotation()[i][plane.axis()]);
        }

        Real centerDistance =
            abs(box.position()[plane.axis()] - plane.position());

        return centerDistance <= radius;
    }

    //! Tests if an aligned plane and an box overlap.
    /*!
   boxOnPositiveSide:
   Filled with the information
   if the center point of the box is on the positive
   side of the plane.

   Returns:
   overlaps(plane, box)
   */
    template <typename Real, int N>
    bool overlaps(
        const AlignedPlane<Real, N>& plane,
        const Box<Real, N>& box,
        bool& boxOnPositiveSide)
    {
        boxOnPositiveSide =
            box.position()[plane.axis()] > plane.position();

        return overlaps(plane, box);
    }

}

#endif