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189 lines
5.7 KiB
189 lines
5.7 KiB
#include "pch.h" // use stdafx.h in Visual Studio 2017 and earlier
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#include "Intersection.h"
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TriangleSegmentIntersectRes::TriangleSegmentIntersectRes(bool h, float tt) : hit(h), t(tt) {} // VS2008
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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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{
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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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{
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return TriangleSegmentIntersectRes(true, s2.dot(e2) / s1_dot_e1);
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}
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return TriangleSegmentIntersectRes(false, 0.f);
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}
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BVHNode::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::BVHNode() : left(0), right(0), parent(0), boundingBox() {}
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BVH_intersection::BVH_intersection(const Mesh &mesh_) : mesh(mesh_)
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{
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faceCenters.reserve(mesh.indices.size());
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for (vector<Vec3u>::const_iterator it = mesh.indices.begin(); it != mesh.indices.end(); ++it)
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{
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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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}
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vector<size_t> indicesList(mesh.indices.size());
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for (size_t i = 0; i < indicesList.size(); ++i)
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{
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indicesList[i] = i;
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}
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try
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{
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nodes.resize(2 * mesh.indices.size() - 1);
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}
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catch (const length_error &e)
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{
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cout << "vector.length:" << nodes.size() << " resize_pa:" << (2 * mesh.indices.size() - 1) << endl;
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cerr << "Caught a length_error: " << e.what() << endl;
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}
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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 BVH_intersection::dfsBuild(vector<size_t> &indicesList, AABB aabb, size_t &nowIdx)
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{
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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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{
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// leaf
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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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{
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const float axisLen = aabb.max[i] - aabb.min[i];
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if (axisLen > longAxisLen)
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{
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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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nth(indicesList, k - 1, longAxis);
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vector<size_t> leftIndices(indicesList.begin(), indicesList.begin() + k);
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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] = 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 BVH_intersection::intersectWithLineSegment(const LineSegment &lineSegment) const
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{
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return recursiveLineSegIntersection(lineSegment, 0);
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}
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AABB BVH_intersection::computeAABB(const vector<size_t> &indices)
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{
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AABB aabb;
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for (vector<size_t>::const_iterator it = indices.begin(); it != indices.end(); ++it)
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{
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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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{
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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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{
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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 BVH_intersection::recursiveLineSegIntersection(const LineSegment &lineSegment, size_t nodeIdx) const
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{
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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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{
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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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{
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swap(t_min, t_max);
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}
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if (t_min > lineSegment.getLength() || t_max < 0)
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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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{
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hit = true;
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}
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}
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if (hit)
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{
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if (nodes[nodeIdx].left == 0)
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{
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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())
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return false;
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return true;
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}
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else
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{
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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 BVH_intersection::nth(vector<size_t> &indicesList, size_t kth, int longAxis)
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{
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recursiveChoose(indicesList, 0, indicesList.size() - 1, kth, longAxis);
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}
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void BVH_intersection::recursiveChoose(vector<size_t> &indicesList, size_t begin, size_t end, size_t kth, int longAxis)
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{
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if (begin >= end)
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return;
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int i = begin, j = end;
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while (i < j)
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{
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while (i < j && faceCenters[indicesList[j]][longAxis] >= faceCenters[indicesList[begin]][longAxis])
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j--;
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while (i < j && faceCenters[indicesList[i]][longAxis] <= faceCenters[indicesList[begin]][longAxis])
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i++;
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swap(indicesList[i], indicesList[j]);
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}
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swap(indicesList[begin], indicesList[i]);
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if (i == kth)
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return;
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if (i < kth)
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recursiveChoose(indicesList, i + 1, end, kth, longAxis);
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else
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recursiveChoose(indicesList, begin, i - 1, kth, longAxis);
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}
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