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212 lines
8.2 KiB
212 lines
8.2 KiB
10 months ago
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#pragma once
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#include <numeric>
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#include <algorithm>
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#include <vector>
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#include <cstddef>
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#include "Geometry.h"
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struct TriangleSegmentIntersectRes {
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bool hit;
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float t;
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TriangleSegmentIntersectRes(bool h,float tt):hit(h),t(tt){}//VS2008
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};
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TriangleSegmentIntersectRes
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triangleSegmentIntersection(const LineSegment &segment, const Vec3f &a, const Vec3f &b, const Vec3f &c) {
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Vec3f e1 = b - a;
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Vec3f e2 = c - a;
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Vec3f s = segment.start - a;
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Vec3f s1 = segment.getDir().cross(e2);
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Vec3f s2 = s.cross(e1);
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float s1_dot_e1 = s1.dot(e1);
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float b1 = s1.dot(s) / s1_dot_e1;
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float b2 = s2.dot(segment.getDir()) / s1_dot_e1;
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if (b1 >= 0. && b2 >= 0. && b1 + b2 <= 1.) {
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// hit
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// return {true, s2.dot(e2) / s1_dot_e1};
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return TriangleSegmentIntersectRes(true, s2.dot(e2) / s1_dot_e1);//VS2008
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}
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// return {false, 0.};
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return TriangleSegmentIntersectRes(false, 0.f);//VS2008
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}
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class BVHNode {
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public:
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size_t left;
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size_t right;
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size_t parent;
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AABB boundingBox;
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BVHNode(size_t l, size_t r, size_t p, const AABB &aabb) : left(l), right(r), parent(p), boundingBox(aabb) {}
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BVHNode() : left(0), right(0), parent(0), boundingBox() {}
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};
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class BVH_intersection {
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public:
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const Mesh &mesh;
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std::vector<Vec3f> faceCenters;
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std::vector<BVHNode> nodes;
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BVH_intersection(const Mesh &mesh_) : mesh(mesh_) {
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faceCenters.reserve(mesh.indices.size());
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// for (const Vec3u &face: mesh.indices) {
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// Vec3f center = (mesh.vertices[face[0]] + mesh.vertices[face[1]] + mesh.vertices[face[2]]) / 3.0f;
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// faceCenters.push_back(center);
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// }
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for (std::vector<Vec3u>::const_iterator it = mesh.indices.begin();it!=mesh.indices.end();++it) {
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const Vec3u& face = *it;
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Vec3f center = (mesh.vertices[face[0]] + mesh.vertices[face[1]] + mesh.vertices[face[2]]) / 3.0f;
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faceCenters.push_back(center);
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}//VS2008
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std::vector<size_t> indicesList(mesh.indices.size());
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// std::iota(indicesList.begin(), indicesList.end(), 0);
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for(size_t i=0;i<indicesList.size();++i){
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indicesList[i]=i;
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}//��������
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try{
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nodes.resize(2 * mesh.indices.size() - 1);
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}catch(const std::length_error& e){
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std::cout<<"vector.length:"<<nodes.size()<<" resize_pa:"<<(2 * mesh.indices.size() - 1)<<std::endl;
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std::cerr<<"Caught a length_error: "<<e.what()<<std::endl;
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}
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//nodes.resize(2 * mesh.indices.size() - 1);
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size_t nowIdx = 0;
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dfsBuild(indicesList, computeAABB(indicesList), nowIdx);
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}
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size_t
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dfsBuild(std::vector<size_t> &indicesList, AABB aabb, size_t &nowIdx) {
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const size_t nodeIdx = nowIdx;
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nowIdx++;
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if (indicesList.size() == 1) {
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// leaf
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// nodes[nodeIdx] = {0, indicesList[0], 0, aabb};
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nodes[nodeIdx] = BVHNode(0, indicesList[0], 0, aabb);//VS2008
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return nodeIdx;
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}
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// longest axis
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int longAxis = -1;
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float longAxisLen = -1;
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for (int i = 0; i < 3; ++i) {
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const float axisLen = aabb.max[i] - aabb.min[i];
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if (axisLen > longAxisLen) {
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longAxisLen = axisLen;
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longAxis = i;
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}
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}
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// split indices list
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const size_t k = indicesList.size() / 2;
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// std::nth_element(indicesList.begin(), indicesList.begin() + k - 1, indicesList.end(),
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// [&](const size_t &a, const size_t &b) {
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// return faceCenters[a][longAxis] < faceCenters[b][longAxis];
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// });
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nth(indicesList, k - 1, longAxis);
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std::vector<size_t> leftIndices(indicesList.begin(), indicesList.begin() + k);
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std::vector<size_t> rightIndices(indicesList.begin() + k, indicesList.end());
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const AABB leftAABB = computeAABB(leftIndices);
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const AABB rightAABB = computeAABB(rightIndices);
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const size_t leftIdx = dfsBuild(leftIndices, leftAABB, nowIdx);
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const size_t rightIdx = dfsBuild(rightIndices, rightAABB, nowIdx);
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// nodes[nodeIdx] = {leftIdx, rightIdx, 0, aabb};
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nodes[nodeIdx] = BVHNode(leftIdx, rightIdx, 0, aabb);//VS2008
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nodes[leftIdx].parent = nodeIdx;
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nodes[rightIdx].parent = nodeIdx;
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return nodeIdx;
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}
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bool intersectWithLineSegment(const LineSegment &lineSegment) const {
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return recursiveLineSegIntersection(lineSegment, 0);
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}
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//private:
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// AABB computeAABB(const std::vector<size_t> &indices) {
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// AABB aabb;
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// for (const size_t &idx: indices) {
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// const Vec3u &face = mesh.indices[idx];
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// for (int i = 0; i < 3; ++i) {
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// const Vec3f &vertex = mesh.vertices[face[i]];
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// for (int j = 0; j < 3; ++j) {
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// aabb.min[j] = std::min(aabb.min[j], vertex[j]);
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// aabb.max[j] = std::max(aabb.max[j], vertex[j]);
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// }
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// }
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// }
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// return {aabb.min, aabb.max};
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// }
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private:
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AABB computeAABB(const std::vector<size_t> &indices) {
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AABB aabb;
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for (std::vector<size_t>::const_iterator it = indices.begin();it!=indices.end();++it) {
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const Vec3u &face = mesh.indices[*it];
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for (int i = 0; i < 3; ++i) {
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const Vec3f &vertex = mesh.vertices[face[i]];
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for (int j = 0; j < 3; ++j) {
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aabb.min[j] = min(aabb.min[j], vertex[j]);
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aabb.max[j] = max(aabb.max[j], vertex[j]);
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}
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}
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}
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return aabb;
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}
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bool recursiveLineSegIntersection(const LineSegment &lineSegment, size_t nodeIdx) const {
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// segment-box intersection test
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const AABB &aabb = nodes[nodeIdx].boundingBox;
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const Vec3f &dir = lineSegment.getDir();
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bool hit = false;
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for (int i = 0; !hit && i < 3; ++i) {
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float t_min = (aabb.min[i] - lineSegment.start[i]) / dir[i];
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float t_max = (aabb.max[i] - lineSegment.start[i]) / dir[i];
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if (t_min > t_max) {
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std::swap(t_min, t_max);
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}
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if (t_min > lineSegment.getLength() || t_max < 0) return false;
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Vec3f hitPt = lineSegment.start + dir * t_min;
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int otherPlane1 = (i + 1) % 3, otherPlane2 = (i + 2) % 3;
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if (hitPt[otherPlane1] >= aabb.min[otherPlane1] && hitPt[otherPlane1] <= aabb.max[otherPlane1] &&
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hitPt[otherPlane2] >= aabb.min[otherPlane2] && hitPt[otherPlane2] <= aabb.max[otherPlane2]) {
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hit = true;
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}
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}
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if (hit) {
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if (nodes[nodeIdx].left == 0) {
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// leaf
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Vec3u face = mesh.indices[nodes[nodeIdx].right];
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TriangleSegmentIntersectRes res = triangleSegmentIntersection(lineSegment, mesh.vertices[face[0]], mesh.vertices[face[1]],
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mesh.vertices[face[2]]);
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if (!res.hit || res.t < 0 || res.t > lineSegment.getLength()) return false;
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return true;
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} else {
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// check children
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return recursiveLineSegIntersection(lineSegment, nodes[nodeIdx].left) ||
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recursiveLineSegIntersection(lineSegment, nodes[nodeIdx].right);
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}
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}
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return false;
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}
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// implement nth, without std::nth_element
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// kth is 0-based
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void nth(std::vector<size_t> &indicesList, size_t kth, int longAxis) {
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recursiveChoose(indicesList, 0, indicesList.size() - 1, kth, longAxis);
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}
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void recursiveChoose(std::vector<size_t> &indicesList, size_t begin, size_t end, size_t kth, int longAxis) {
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if (begin >= end) return;
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int i = begin, j = end;
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while (i < j) {
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while (i < j && faceCenters[indicesList[j]][longAxis] >= faceCenters[indicesList[begin]][longAxis]) j--;
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while (i < j && faceCenters[indicesList[i]][longAxis] <= faceCenters[indicesList[begin]][longAxis]) i++;
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std::swap(indicesList[i], indicesList[j]);
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}
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std::swap(indicesList[begin], indicesList[i]);
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if (i == kth) return;
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if (i < kth) recursiveChoose(indicesList, i + 1, end, kth, longAxis);
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else recursiveChoose(indicesList, begin, i - 1, kth, longAxis);
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}
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};
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