octree.cpp

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#include "precomp.hpp"
#include <limits>

namespace
{
    using namespace cv;
    const size_t MAX_STACK_SIZE = 255;
    const size_t MAX_LEAFS = 8;

    bool checkIfNodeOutsideSphere(const Octree::Node& node, const Point3f& c, float r)
    {
        if (node.x_max < (c.x - r) ||  node.y_max < (c.y - r) || node.z_max < (c.z - r))
            return true;

        if ((c.x + r) < node.x_min || (c.y + r) < node.y_min || (c.z + r) < node.z_min)
            return true;

        return false;
    }

    bool checkIfNodeInsideSphere(const Octree::Node& node, const Point3f& c, float r)
    {
        r *= r;

        float d2_xmin = (node.x_min - c.x) * (node.x_min - c.x);
        float d2_ymin = (node.y_min - c.y) * (node.y_min - c.y);
        float d2_zmin = (node.z_min - c.z) * (node.z_min - c.z);

        if (d2_xmin + d2_ymin + d2_zmin > r)
            return false;

        float d2_zmax = (node.z_max - c.z) * (node.z_max - c.z);

        if (d2_xmin + d2_ymin + d2_zmax > r)
            return false;

        float d2_ymax = (node.y_max - c.y) * (node.y_max - c.y);

        if (d2_xmin + d2_ymax + d2_zmin > r)
            return false;

        if (d2_xmin + d2_ymax + d2_zmax > r)
            return false;

        float d2_xmax = (node.x_max - c.x) * (node.x_max - c.x);

        if (d2_xmax + d2_ymin + d2_zmin > r)
            return false;

        if (d2_xmax + d2_ymin + d2_zmax > r)
            return false;

        if (d2_xmax + d2_ymax + d2_zmin > r)
            return false;

        if (d2_xmax + d2_ymax + d2_zmax > r)
            return false;

        return true;
    }

    void fillMinMax(const std::vector<Point3f>& points, Octree::Node& node)
    {
        node.x_max = node.y_max = node.z_max = std::numeric_limits<float>::min();
        node.x_min = node.y_min = node.z_min = std::numeric_limits<float>::max();

        for (size_t i = 0; i < points.size(); ++i)
        {
            const Point3f& point = points[i];

            if (node.x_max < point.x)
                node.x_max = point.x;

            if (node.y_max < point.y)
                node.y_max = point.y;

            if (node.z_max < point.z)
                node.z_max = point.z;

            if (node.x_min > point.x)
                node.x_min = point.x;

            if (node.y_min > point.y)
                node.y_min = point.y;

            if (node.z_min > point.z)
                node.z_min = point.z;
        }
    }

    size_t findSubboxForPoint(const Point3f& point, const Octree::Node& node)
    {
        size_t ind_x = point.x < (node.x_max + node.x_min) / 2 ? 0 : 1;
        size_t ind_y = point.y < (node.y_max + node.y_min) / 2 ? 0 : 1;
        size_t ind_z = point.z < (node.z_max + node.z_min) / 2 ? 0 : 1;

        return (ind_x << 2) + (ind_y << 1) + (ind_z << 0);
    }
    void initChildBox(const Octree::Node& parent, size_t boxIndex, Octree::Node& child)
    {
        child.x_min = child.x_max = (parent.x_max + parent.x_min) / 2;
        child.y_min = child.y_max = (parent.y_max + parent.y_min) / 2;
        child.z_min = child.z_max = (parent.z_max + parent.z_min) / 2;

        if ((boxIndex >> 0) & 1)
            child.z_max = parent.z_max;
        else
            child.z_min = parent.z_min;

        if ((boxIndex >> 1) & 1)
            child.y_max = parent.y_max;
        else
            child.y_min = parent.y_min;

        if ((boxIndex >> 2) & 1)
            child.x_max = parent.x_max;
        else
            child.x_min = parent.x_min;
    }

}//namespace

////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////       Octree       //////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////
namespace cv
{
    Octree::Octree()
    {
    }

    Octree::Octree(const std::vector<Point3f>& points3d, int maxLevels, int _minPoints)
    {
        buildTree(points3d, maxLevels, _minPoints);
    }

    Octree::~Octree()
    {
    }

    void Octree::getPointsWithinSphere(const Point3f& center, float radius, std::vector<Point3f>& out) const
    {
        out.clear();

        if (nodes.empty())
            return;

        int stack[MAX_STACK_SIZE];
        int pos = 0;
        stack[pos] = 0;

        while (pos >= 0)
        {
            const Node& cur = nodes[stack[pos--]];

            if (checkIfNodeOutsideSphere(cur, center, radius))
                continue;

            if (checkIfNodeInsideSphere(cur, center, radius))
            {
                size_t sz = out.size();
                out.resize(sz + cur.end - cur.begin);
                for (int i = cur.begin; i < cur.end; ++i)
                    out[sz++] = points[i];
                continue;
            }

            if (cur.isLeaf)
            {
                double r2 = radius * radius;
                size_t sz = out.size();
                out.resize(sz + (cur.end - cur.begin));

                for (int i = cur.begin; i < cur.end; ++i)
                {
                    const Point3f& point = points[i];

                    double dx = (point.x - center.x);
                    double dy = (point.y - center.y);
                    double dz = (point.z - center.z);

                    double dist2 = dx * dx + dy * dy + dz * dz;

                    if (dist2 < r2)
                        out[sz++] = point;
                };
                out.resize(sz);
                continue;
            }

            if (cur.children[0])
                stack[++pos] = cur.children[0];

            if (cur.children[1])
                stack[++pos] = cur.children[1];

            if (cur.children[2])
                stack[++pos] = cur.children[2];

            if (cur.children[3])
                stack[++pos] = cur.children[3];

            if (cur.children[4])
                stack[++pos] = cur.children[4];

            if (cur.children[5])
                stack[++pos] = cur.children[5];

            if (cur.children[6])
                stack[++pos] = cur.children[6];

            if (cur.children[7])
                stack[++pos] = cur.children[7];
        }
    }

    void Octree::buildTree(const std::vector<Point3f>& points3d, int maxLevels, int _minPoints)
    {
        CV_Assert((size_t)maxLevels * 8 < MAX_STACK_SIZE);
        points.resize(points3d.size());
        std::copy(points3d.begin(), points3d.end(), points.begin());
        minPoints = _minPoints;

        nodes.clear();
        nodes.push_back(Node());
        Node& root = nodes[0];
        fillMinMax(points, root);

        root.isLeaf = true;
        root.maxLevels = maxLevels;
        root.begin = 0;
        root.end = (int)points.size();
        for (size_t i = 0; i < MAX_LEAFS; i++)
            root.children[i] = 0;

        if (maxLevels != 1 && (root.end - root.begin) > _minPoints)
        {
            root.isLeaf = false;
            buildNext(0);
        }
    }

    void  Octree::buildNext(size_t nodeInd)
    {
        size_t size = nodes[nodeInd].end - nodes[nodeInd].begin;

        std::vector<size_t> boxBorders(MAX_LEAFS+1, 0);
        std::vector<size_t> boxIndices(size);
        std::vector<Point3f> tempPoints(size);

        for (int i = nodes[nodeInd].begin, j = 0; i < nodes[nodeInd].end; ++i, ++j)
        {
            const Point3f& p = points[i];

            size_t subboxInd = findSubboxForPoint(p, nodes[nodeInd]);

            boxBorders[subboxInd+1]++;
            boxIndices[j] = subboxInd;
            tempPoints[j] = p;
        }

        for (size_t i = 1; i < boxBorders.size(); ++i)
            boxBorders[i] += boxBorders[i-1];

        std::vector<size_t> writeInds(boxBorders.begin(), boxBorders.end());

        for (size_t i = 0; i < size; ++i)
        {
            size_t boxIndex = boxIndices[i];
            Point3f& curPoint = tempPoints[i];

            size_t copyTo = nodes[nodeInd].begin + writeInds[boxIndex]++;
            points[copyTo] = curPoint;
        }

        for (size_t i = 0; i < MAX_LEAFS; ++i)
        {
            if (boxBorders[i] == boxBorders[i+1])
                continue;

            nodes.push_back(Node());
            Node& child = nodes.back();
            initChildBox(nodes[nodeInd], i, child);

            child.isLeaf = true;
            child.maxLevels = nodes[nodeInd].maxLevels - 1;
            child.begin = nodes[nodeInd].begin + (int)boxBorders[i+0];
            child.end   = nodes[nodeInd].begin + (int)boxBorders[i+1];
            for (size_t k = 0; k < MAX_LEAFS; k++)
                child.children[k] = 0;

            nodes[nodeInd].children[i] = (int)(nodes.size() - 1);

            if (child.maxLevels != 1 && (child.end - child.begin) > minPoints)
            {
                child.isLeaf = false;
                buildNext(nodes.size() - 1);
            }
        }
    }

}