slidingmidpoint_splitrule.h

// Description: Sliding midpoint splitting rule

#ifndef PASTELGEOMETRY_SLIDINGMIDPOINT_SPLITRULE_H
#define PASTELGEOMETRY_SLIDINGMIDPOINT_SPLITRULE_H

#include "pastel/sys/pointset/pointset_concept.h"
#include "pastel/sys/locator/locator_concept.h"

#include "pastel/geometry/splitrule/splitrule_concept.h"
#include "pastel/geometry/shape/alignedbox.h"

namespace Pastel
{

    //! Sliding midpoint splitting rule.
    class SlidingMidpoint_SplitRule
    {
    public:
        template <
            PointSet_Concept PointSet,
            typename Real = PointSet_Real<PointSet>,
            int N = PointSet_Dimension<PointSet>::value
        >
        std::pair<Real, integer> operator()(
            const PointSet& pointSet,
            const AlignedBox<Real, N>& bound) const
        {
            // Split along the longest dimension.
            integer splitAxis = maxIndex(bound.extent());

            // First try the mid-point of the bounding box.
            Real splitPosition = linear(
                bound.min()[splitAxis], 
                bound.max()[splitAxis], 0.5);

            if (isEmptyRange(pointSet))
            {
                return std::make_pair(splitPosition, splitAxis);
            }

            // Sliding mid-point

            Real leftMax = -Infinity();
            integer leftCount = 0;

            Real rightMin = Infinity();
            integer rightCount = 0;

            for (auto&& point : pointSet)
            {
                Real position = pointAxis(point, splitAxis);
                if (position < splitPosition)
                {
                    if (position > leftMax)
                    {
                        leftMax = position;
                    }
                    ++leftCount;
                }
                else
                {
                    if (position < rightMin)
                    {
                        rightMin = position;
                    }
                    ++rightCount;
                }
            }

            if (leftCount == 0)
            {
                splitPosition = rightMin;
            }
            else if (rightCount == 0)
            {
                splitPosition = leftMax;
            }

            return std::make_pair(splitPosition, splitAxis);
        }
    };

}

#endif