box_area.hpp

#ifndef PASTELGEOMETRY_BOX_AREA_HPP
#define PASTELGEOMETRY_BOX_AREA_HPP

#include "pastel/geometry/area/box_area.h"

#include "pastel/sys/vector/vector_tools.h"

namespace Pastel
{

    template <typename Real, integer N>
    Real area(const AlignedBox<Real, N>& box)
    {
        return boxArea(box.max() - box.min());
    }

    template <typename Real, integer N>
    Real area(const Box<Real, N>& box)
    {
        return boxArea(2 * box.width());
    }

    template <typename Real, typename Expression>
    Real boxArea(const VectorExpression<Real, 1, Expression>& width)
    {
        return 0;
    }

    template <typename Real, integer N, typename Expression>
    Real boxArea(const VectorExpression<Real, N, Expression>& width)
    {
        // area = 2 * sum_i(width[0] * ... * width[i - 1] * width[i + 1] * ... * width[N])
        //
        // Note that even if the box has volume 0, it can still
        // have area (if exactly one of width[i] is zero).

        integer dimension = width.size();

        Real result = 0;

        for (integer i = 0;i < dimension;++i)
        {
            Real faceArea = 1;
            for (integer k = 0;k < i;++k)
            {

                faceArea *= width[k];
            }
            for (integer k = i + 1;k < dimension;++k)
            {
                faceArea *= width[k];
            }

            result += faceArea;
        }

        return 2 * result;
    }

}

#endif