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authorNao Pross <np@0hm.ch>2024-02-12 14:52:43 +0100
committerNao Pross <np@0hm.ch>2024-02-12 14:52:43 +0100
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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2009 Ilya Baran <ibaran@mit.edu>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_BVH_MODULE_H
+#define EIGEN_BVH_MODULE_H
+
+#include "../../Eigen/Core"
+#include "../../Eigen/Geometry"
+#include "../../Eigen/StdVector"
+#include <algorithm>
+#include <queue>
+
+namespace Eigen {
+
+/**
+ * \defgroup BVH_Module BVH module
+ * \brief This module provides generic bounding volume hierarchy algorithms
+ * and reference tree implementations.
+ *
+ *
+ * \code
+ * #include <unsupported/Eigen/BVH>
+ * \endcode
+ *
+ * A bounding volume hierarchy (BVH) can accelerate many geometric queries. This module provides a generic implementation
+ * of the two basic algorithms over a BVH: intersection of a query object against all objects in the hierarchy and minimization
+ * of a function over the objects in the hierarchy. It also provides intersection and minimization over a cartesian product of
+ * two BVH's. A BVH accelerates intersection by using the fact that if a query object does not intersect a volume, then it cannot
+ * intersect any object contained in that volume. Similarly, a BVH accelerates minimization because the minimum of a function
+ * over a volume is no greater than the minimum of a function over any object contained in it.
+ *
+ * Some sample queries that can be written in terms of intersection are:
+ * - Determine all points where a ray intersects a triangle mesh
+ * - Given a set of points, determine which are contained in a query sphere
+ * - Given a set of spheres, determine which contain the query point
+ * - Given a set of disks, determine if any is completely contained in a query rectangle (represent each 2D disk as a point \f$(x,y,r)\f$
+ * in 3D and represent the rectangle as a pyramid based on the original rectangle and shrinking in the \f$r\f$ direction)
+ * - Given a set of points, count how many pairs are \f$d\pm\epsilon\f$ apart (done by looking at the cartesian product of the set
+ * of points with itself)
+ *
+ * Some sample queries that can be written in terms of function minimization over a set of objects are:
+ * - Find the intersection between a ray and a triangle mesh closest to the ray origin (function is infinite off the ray)
+ * - Given a polyline and a query point, determine the closest point on the polyline to the query
+ * - Find the diameter of a point cloud (done by looking at the cartesian product and using negative distance as the function)
+ * - Determine how far two meshes are from colliding (this is also a cartesian product query)
+ *
+ * This implementation decouples the basic algorithms both from the type of hierarchy (and the types of the bounding volumes) and
+ * from the particulars of the query. To enable abstraction from the BVH, the BVH is required to implement a generic mechanism
+ * for traversal. To abstract from the query, the query is responsible for keeping track of results.
+ *
+ * To be used in the algorithms, a hierarchy must implement the following traversal mechanism (see KdBVH for a sample implementation): \code
+ typedef Volume //the type of bounding volume
+ typedef Object //the type of object in the hierarchy
+ typedef Index //a reference to a node in the hierarchy--typically an int or a pointer
+ typedef VolumeIterator //an iterator type over node children--returns Index
+ typedef ObjectIterator //an iterator over object (leaf) children--returns const Object &
+ Index getRootIndex() const //returns the index of the hierarchy root
+ const Volume &getVolume(Index index) const //returns the bounding volume of the node at given index
+ void getChildren(Index index, VolumeIterator &outVBegin, VolumeIterator &outVEnd,
+ ObjectIterator &outOBegin, ObjectIterator &outOEnd) const
+ //getChildren takes a node index and makes [outVBegin, outVEnd) range over its node children
+ //and [outOBegin, outOEnd) range over its object children
+ \endcode
+ *
+ * To use the hierarchy, call BVIntersect or BVMinimize, passing it a BVH (or two, for cartesian product) and a minimizer or intersector.
+ * For an intersection query on a single BVH, the intersector encapsulates the query and must provide two functions:
+ * \code
+ bool intersectVolume(const Volume &volume) //returns true if the query intersects the volume
+ bool intersectObject(const Object &object) //returns true if the intersection search should terminate immediately
+ \endcode
+ * The guarantee that BVIntersect provides is that intersectObject will be called on every object whose bounding volume
+ * intersects the query (but possibly on other objects too) unless the search is terminated prematurely. It is the
+ * responsibility of the intersectObject function to keep track of the results in whatever manner is appropriate.
+ * The cartesian product intersection and the BVMinimize queries are similar--see their individual documentation.
+ *
+ * The following is a simple but complete example for how to use the BVH to accelerate the search for a closest red-blue point pair:
+ * \include BVH_Example.cpp
+ * Output: \verbinclude BVH_Example.out
+ */
+}
+
+//@{
+
+#include "src/BVH/BVAlgorithms.h"
+#include "src/BVH/KdBVH.h"
+
+//@}
+
+#endif // EIGEN_BVH_MODULE_H