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KdBVH.h
1// This file is part of Eigen, a lightweight C++ template library
2// for linear algebra.
3//
4// Copyright (C) 2009 Ilya Baran <ibaran@mit.edu>
5//
6// This Source Code Form is subject to the terms of the Mozilla
7// Public License v. 2.0. If a copy of the MPL was not distributed
8// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9
10#ifndef KDBVH_H_INCLUDED
11#define KDBVH_H_INCLUDED
12
13namespace Eigen {
14
15namespace internal {
16
17//internal pair class for the BVH--used instead of std::pair because of alignment
18template<typename Scalar, int Dim>
19struct vector_int_pair
20{
21EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF_VECTORIZABLE_FIXED_SIZE(Scalar, Dim)
22 typedef Matrix<Scalar, Dim, 1> VectorType;
23
24 vector_int_pair(const VectorType &v, int i) : first(v), second(i) {}
25
26 VectorType first;
27 int second;
28};
29
30//these templates help the tree initializer get the bounding boxes either from a provided
31//iterator range or using bounding_box in a unified way
32template<typename ObjectList, typename VolumeList, typename BoxIter>
33struct get_boxes_helper {
34 void operator()(const ObjectList &objects, BoxIter boxBegin, BoxIter boxEnd, VolumeList &outBoxes)
35 {
36 outBoxes.insert(outBoxes.end(), boxBegin, boxEnd);
37 eigen_assert(outBoxes.size() == objects.size());
38 }
39};
40
41template<typename ObjectList, typename VolumeList>
42struct get_boxes_helper<ObjectList, VolumeList, int> {
43 void operator()(const ObjectList &objects, int, int, VolumeList &outBoxes)
44 {
45 outBoxes.reserve(objects.size());
46 for(int i = 0; i < (int)objects.size(); ++i)
47 outBoxes.push_back(bounding_box(objects[i]));
48 }
49};
50
51} // end namespace internal
52
53
67template<typename _Scalar, int _Dim, typename _Object> class KdBVH
68{
69public:
70 enum { Dim = _Dim };
71 typedef _Object Object;
72 typedef std::vector<Object, aligned_allocator<Object> > ObjectList;
73 typedef _Scalar Scalar;
74 typedef AlignedBox<Scalar, Dim> Volume;
75 typedef std::vector<Volume, aligned_allocator<Volume> > VolumeList;
76 typedef int Index;
77 typedef const int *VolumeIterator; //the iterators are just pointers into the tree's vectors
78 typedef const Object *ObjectIterator;
79
80 KdBVH() {}
81
83 template<typename Iter> KdBVH(Iter begin, Iter end) { init(begin, end, 0, 0); } //int is recognized by init as not being an iterator type
84
86 template<typename OIter, typename BIter> KdBVH(OIter begin, OIter end, BIter boxBegin, BIter boxEnd) { init(begin, end, boxBegin, boxEnd); }
87
90 template<typename Iter> void init(Iter begin, Iter end) { init(begin, end, 0, 0); }
91
94 template<typename OIter, typename BIter> void init(OIter begin, OIter end, BIter boxBegin, BIter boxEnd)
95 {
96 objects.clear();
97 boxes.clear();
98 children.clear();
99
100 objects.insert(objects.end(), begin, end);
101 int n = static_cast<int>(objects.size());
102
103 if(n < 2)
104 return; //if we have at most one object, we don't need any internal nodes
105
106 VolumeList objBoxes;
107 VIPairList objCenters;
108
109 //compute the bounding boxes depending on BIter type
110 internal::get_boxes_helper<ObjectList, VolumeList, BIter>()(objects, boxBegin, boxEnd, objBoxes);
111
112 objCenters.reserve(n);
113 boxes.reserve(n - 1);
114 children.reserve(2 * n - 2);
115
116 for(int i = 0; i < n; ++i)
117 objCenters.push_back(VIPair(objBoxes[i].center(), i));
118
119 build(objCenters, 0, n, objBoxes, 0); //the recursive part of the algorithm
120
121 ObjectList tmp(n);
122 tmp.swap(objects);
123 for(int i = 0; i < n; ++i)
124 objects[i] = tmp[objCenters[i].second];
125 }
126
128 inline Index getRootIndex() const { return (int)boxes.size() - 1; }
129
132 EIGEN_STRONG_INLINE void getChildren(Index index, VolumeIterator &outVBegin, VolumeIterator &outVEnd,
133 ObjectIterator &outOBegin, ObjectIterator &outOEnd) const
134 { //inlining this function should open lots of optimization opportunities to the compiler
135 if(index < 0) {
136 outVBegin = outVEnd;
137 if(!objects.empty())
138 outOBegin = &(objects[0]);
139 outOEnd = outOBegin + objects.size(); //output all objects--necessary when the tree has only one object
140 return;
141 }
142
143 int numBoxes = static_cast<int>(boxes.size());
144
145 int idx = index * 2;
146 if(children[idx + 1] < numBoxes) { //second index is always bigger
147 outVBegin = &(children[idx]);
148 outVEnd = outVBegin + 2;
149 outOBegin = outOEnd;
150 }
151 else if(children[idx] >= numBoxes) { //if both children are objects
152 outVBegin = outVEnd;
153 outOBegin = &(objects[children[idx] - numBoxes]);
154 outOEnd = outOBegin + 2;
155 } else { //if the first child is a volume and the second is an object
156 outVBegin = &(children[idx]);
157 outVEnd = outVBegin + 1;
158 outOBegin = &(objects[children[idx + 1] - numBoxes]);
159 outOEnd = outOBegin + 1;
160 }
161 }
162
164 inline const Volume &getVolume(Index index) const
165 {
166 return boxes[index];
167 }
168
169private:
170 typedef internal::vector_int_pair<Scalar, Dim> VIPair;
171 typedef std::vector<VIPair, aligned_allocator<VIPair> > VIPairList;
172 typedef Matrix<Scalar, Dim, 1> VectorType;
173 struct VectorComparator //compares vectors, or, more specificall, VIPairs along a particular dimension
174 {
175 VectorComparator(int inDim) : dim(inDim) {}
176 inline bool operator()(const VIPair &v1, const VIPair &v2) const { return v1.first[dim] < v2.first[dim]; }
177 int dim;
178 };
179
180 //Build the part of the tree between objects[from] and objects[to] (not including objects[to]).
181 //This routine partitions the objCenters in [from, to) along the dimension dim, recursively constructs
182 //the two halves, and adds their parent node. TODO: a cache-friendlier layout
183 void build(VIPairList &objCenters, int from, int to, const VolumeList &objBoxes, int dim)
184 {
185 eigen_assert(to - from > 1);
186 if(to - from == 2) {
187 boxes.push_back(objBoxes[objCenters[from].second].merged(objBoxes[objCenters[from + 1].second]));
188 children.push_back(from + (int)objects.size() - 1); //there are objects.size() - 1 tree nodes
189 children.push_back(from + (int)objects.size());
190 }
191 else if(to - from == 3) {
192 int mid = from + 2;
193 std::nth_element(objCenters.begin() + from, objCenters.begin() + mid,
194 objCenters.begin() + to, VectorComparator(dim)); //partition
195 build(objCenters, from, mid, objBoxes, (dim + 1) % Dim);
196 int idx1 = (int)boxes.size() - 1;
197 boxes.push_back(boxes[idx1].merged(objBoxes[objCenters[mid].second]));
198 children.push_back(idx1);
199 children.push_back(mid + (int)objects.size() - 1);
200 }
201 else {
202 int mid = from + (to - from) / 2;
203 nth_element(objCenters.begin() + from, objCenters.begin() + mid,
204 objCenters.begin() + to, VectorComparator(dim)); //partition
205 build(objCenters, from, mid, objBoxes, (dim + 1) % Dim);
206 int idx1 = (int)boxes.size() - 1;
207 build(objCenters, mid, to, objBoxes, (dim + 1) % Dim);
208 int idx2 = (int)boxes.size() - 1;
209 boxes.push_back(boxes[idx1].merged(boxes[idx2]));
210 children.push_back(idx1);
211 children.push_back(idx2);
212 }
213 }
214
215 std::vector<int> children; //children of x are children[2x] and children[2x+1], indices bigger than boxes.size() index into objects.
216 VolumeList boxes;
217 ObjectList objects;
218};
219
220} // end namespace Eigen
221
222#endif //KDBVH_H_INCLUDED
A simple bounding volume hierarchy based on AlignedBox.
Definition: KdBVH.h:68
void init(OIter begin, OIter end, BIter boxBegin, BIter boxEnd)
Definition: KdBVH.h:94
void init(Iter begin, Iter end)
Definition: KdBVH.h:90
Index getRootIndex() const
Definition: KdBVH.h:128
KdBVH(Iter begin, Iter end)
Definition: KdBVH.h:83
KdBVH(OIter begin, OIter end, BIter boxBegin, BIter boxEnd)
Definition: KdBVH.h:86
const Volume & getVolume(Index index) const
Definition: KdBVH.h:164
void getChildren(Index index, VolumeIterator &outVBegin, VolumeIterator &outVEnd, ObjectIterator &outOBegin, ObjectIterator &outOEnd) const
Definition: KdBVH.h:132
Namespace containing all symbols from the Eigen library.
Definition: AdolcForward:45