BVHTree.hpp

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/**\file BVHTree.hpp
 * \class moab::BVHTree
 * \brief Bounding Volume Hierarchy (sorta like a tree), for sorting and searching entities
 * spatially
 */

#ifndef BVH_TREE_HPP
#define BVH_TREE_HPP

#include "moab/Interface.hpp"
#include "moab/CartVect.hpp"
#include "moab/BoundBox.hpp"
#include "moab/Tree.hpp"
#include "moab/Range.hpp"
#include "moab/CN.hpp"

#include <vector>
#include <cfloat>
#include <climits>
#include <map>
#include <set>
#include <iostream>

#include "moab/win32_config.h"

namespace moab
{

class ElemEvaluator;

class BVHTree : public Tree
{
  public:
    BVHTree( Interface* impl );

    ~BVHTree()
    {
        reset_tree();
    }

    /** \brief Destroy the tree maintained by this object, optionally checking we have the right
     * root. \param root If non-NULL, check that this is the root, return failure if not
     */
    virtual ErrorCode reset_tree();

    virtual ErrorCode parse_options( FileOptions& opts );

    /** \brief Get bounding box for tree below tree_node, or entire tree
     * If no tree has been built yet, returns +/- DBL_MAX for all dimensions.  Note for some tree
     * types, boxes are not available for non-root nodes, and this function will return failure if
     * non-root is passed in \param box The box for this tree \param tree_node If non-NULL, node for
     * which box is requested, tree root if NULL \return Only returns error on fatal condition
     */
    virtual ErrorCode get_bounding_box( BoundBox& box, EntityHandle* tree_node = NULL ) const;

    /** Build the tree
     * Build a tree with the entities input.  If a non-NULL tree_root_set pointer is input,
     * use the pointed-to set as the root of this tree (*tree_root_set!=0) otherwise construct
     * a new root set and pass its handle back in *tree_root_set.  Options vary by tree type;
     * see Tree.hpp for common options; options specific to AdaptiveKDTree:
     * SPLITS_PER_DIR: number of candidate splits considered per direction; default = 3
     * CANDIDATE_PLANE_SET: method used to decide split planes; see CandidatePlaneSet enum (below)
     *          for possible values; default = 1 (SUBDIVISION_SNAP)
     * \param entities Entities with which to build the tree
     * \param tree_root Root set for tree (see function description)
     * \param opts Options for tree (see function description)
     * \return Error is returned only on build failure
     */
    virtual ErrorCode build_tree( const Range& entities, EntityHandle* tree_root_set = NULL,
                                  FileOptions* options = NULL );

    /** \brief Get leaf containing input position.
     *
     * Does not take into account global bounding box of tree.
     * - Therefore there is always one leaf containing the point.
     * - If caller wants to account for global bounding box, then
     * caller can test against that box and not call this method
     * at all if the point is outside the box, as there is no leaf
     * containing the point in that case.
     * \param point Point to be located in tree
     * \param leaf_out Leaf containing point
     * \param iter_tol Tolerance for convergence of point search
     * \param inside_tol Tolerance for inside element calculation
     * \param multiple_leaves Some tree types can have multiple leaves containing a point;
     *          if non-NULL, this parameter is returned true if multiple leaves contain
     *          the input point
     * \param start_node Start from this tree node (non-NULL) instead of tree root (NULL)
     * \return Non-success returned only in case of failure; not-found indicated by leaf_out=0
     */
    virtual ErrorCode point_search( const double* point, EntityHandle& leaf_out, const double iter_tol = 1.0e-10,
                                    const double inside_tol = 1.0e-6, bool* multiple_leaves = NULL,
                                    EntityHandle* start_node = NULL, CartVect* params = NULL );

    /** \brief Find all leaves within a given distance from point
     * If dists_out input non-NULL, also returns distances from each leaf; if
     * point i is inside leaf, 0 is given as dists_out[i].
     * If params_out is non-NULL and myEval is non-NULL, will evaluate individual entities
     * in tree nodes and return containing entities in leaves_out.  In those cases, if params_out
     * is also non-NULL, will return parameters in those elements in that vector.
     * \param from_point Point to be located in tree
     * \param distance Distance within which to query
     * \param result_list Leaves within distance or containing point
     * \param iter_tol Tolerance for convergence of point search
     * \param inside_tol Tolerance for inside element calculation
     * \param result_dists If non-NULL, will contain distsances to leaves
     * \param result_params If non-NULL, will contain parameters of the point in the ents in
     * leaves_out \param tree_root Start from this tree node (non-NULL) instead of tree root (NULL)
     */
    virtual ErrorCode distance_search( const double from_point[3], const double distance,
                                       std::vector< EntityHandle >& result_list, const double iter_tol = 1.0e-10,
                                       const double inside_tol = 1.0e-6, std::vector< double >* result_dists = NULL,
                                       std::vector< CartVect >* result_params = NULL, EntityHandle* tree_root = NULL );

    //! print various things about this tree
    virtual ErrorCode print();

  private:
    // don't allow copy constructor, too complicated
    BVHTree( const BVHTree& s );

    class HandleData
    {
      public:
        HandleData( EntityHandle h, const BoundBox& bx, const double dp ) : myHandle( h ), myBox( bx ), myDim( dp ) {}
        HandleData() : myHandle( 0 ), myDim( -1 ) {}
        EntityHandle myHandle;
        BoundBox myBox;
        double myDim;
    };
    typedef std::vector< HandleData > HandleDataVec;

    class SplitData
    {
      public:
        SplitData()
            : dim( UINT_MAX ), nl( UINT_MAX ), nr( UINT_MAX ), split( DBL_MAX ), Lmax( -DBL_MAX ), Rmin( DBL_MAX )
        {
        }
        SplitData( const SplitData& f )
            : dim( f.dim ), nl( f.nl ), nr( f.nr ), split( f.split ), Lmax( f.Lmax ), Rmin( f.Rmin ),
              boundingBox( f.boundingBox ), leftBox( f.leftBox ), rightBox( f.rightBox )
        {
        }
        unsigned int dim, nl, nr;
        double split;
        double Lmax, Rmin;
        BoundBox boundingBox, leftBox, rightBox;
        SplitData& operator=( const SplitData& f )
        {
            dim         = f.dim;
            nl          = f.nl;
            nr          = f.nr;
            split       = f.split;
            Lmax        = f.Lmax;
            Rmin        = f.Rmin;
            boundingBox = f.boundingBox;
            leftBox     = f.leftBox;
            rightBox    = f.rightBox;
            return *this;
        }
    };  // SplitData

    class Split_comparator : public std::binary_function< SplitData, SplitData, bool >
    {
        inline double objective( const SplitData& a ) const
        {
            return a.Lmax * a.nl - a.Rmin * a.nr;
        }

      public:
        bool operator()( const SplitData& a, const SplitData& b ) const
        {
            return objective( a ) < objective( b );
        }
    };  // Split_comparator

    class HandleData_comparator : public std::binary_function< HandleData, HandleData, bool >
    {
      public:
        bool operator()( const HandleData& a, const HandleData& b )
        {
            return a.myDim < b.myDim || ( a.myDim == b.myDim && a.myHandle < b.myHandle );
        }
    };  // Iterator_comparator

    class Bucket
    {
      public:
        Bucket() : mySize( 0 ) {}
        Bucket( const Bucket& f ) : mySize( f.mySize ), boundingBox( f.boundingBox ) {}
        Bucket( const unsigned int sz ) : mySize( sz ) {}
        static unsigned int bucket_index( int num_splits, const BoundBox& box, const BoundBox& interval,
                                          const unsigned int dim );
        unsigned int mySize;
        BoundBox boundingBox;
        Bucket& operator=( const Bucket& f )
        {
            boundingBox = f.boundingBox;
            mySize      = f.mySize;
            return *this;
        }
    };  // Bucket

    class Node
    {
      public:
        HandleDataVec entities;
        unsigned int dim, child;
        double Lmax, Rmin;
        BoundBox box;
        Node() : dim( UINT_MAX ), child( UINT_MAX ), Lmax( -DBL_MAX ), Rmin( DBL_MAX ) {}
        Node& operator=( const Node& f )
        {
            dim      = f.dim;
            child    = f.child;
            Lmax     = f.Lmax;
            Rmin     = f.Rmin;
            entities = f.entities;
            return *this;
        }
    };  // Node

    class TreeNode
    {
      public:
        unsigned int dim, child;
        double Lmax, Rmin;
        BoundBox box;
        TreeNode( int dm, int chld, double lmx, double rmn, BoundBox& bx )
            : dim( dm ), child( chld ), Lmax( lmx ), Rmin( rmn ), box( bx )
        {
        }
        TreeNode& operator=( const TreeNode& f )
        {
            dim   = f.dim;
            child = f.child;
            Lmax  = f.Lmax;
            Rmin  = f.Rmin;
            return *this;
        }
    };  // TreeNode

    void establish_buckets( HandleDataVec::const_iterator begin, HandleDataVec::const_iterator end,
                            const BoundBox& interval, std::vector< std::vector< Bucket > >& buckets ) const;

    unsigned int set_interval( BoundBox& interval, std::vector< Bucket >::const_iterator begin,
                               std::vector< Bucket >::const_iterator end ) const;

    void initialize_splits( std::vector< std::vector< SplitData > >& splits,
                            const std::vector< std::vector< Bucket > >& buckets, const SplitData& data ) const;

    void order_elements( HandleDataVec::iterator& begin, HandleDataVec::iterator& end, SplitData& data ) const;

    void median_order( HandleDataVec::iterator& begin, HandleDataVec::iterator& end, SplitData& data ) const;

    void choose_best_split( const std::vector< std::vector< SplitData > >& splits, SplitData& data ) const;

    void find_split( HandleDataVec::iterator& begin, HandleDataVec::iterator& end, SplitData& data ) const;

    ErrorCode find_point( const std::vector< double >& point, const unsigned int& index, const double iter_tol,
                          const double inside_tol, std::pair< EntityHandle, CartVect >& result );

    EntityHandle bruteforce_find( const double* point, const double iter_tol = 1.0e-10,
                                  const double inside_tol = 1.0e-6 );

    int local_build_tree( std::vector< Node >& tree_nodes, HandleDataVec::iterator begin, HandleDataVec::iterator end,
                          const int index, const BoundBox& box, const int depth = 0 );

    // builds up vector of HandleData, which caches elements' bounding boxes
    ErrorCode construct_element_vec( std::vector< HandleData >& handle_data_vec, const Range& elements,
                                     BoundBox& bounding_box );

    // convert the std::vector<Node> to myTree and a bunch of entity sets
    ErrorCode convert_tree( std::vector< Node >& tree_nodes );

    // print tree nodes
    ErrorCode print_nodes( std::vector< Node >& nodes );

    Range entityHandles;
    std::vector< TreeNode > myTree;
    int splitsPerDir;
    EntityHandle startSetHandle;
    static MOAB_EXPORT const char* treeName;
};  // class Bvh_tree

inline unsigned int BVHTree::Bucket::bucket_index( int num_splits, const BoundBox& box, const BoundBox& interval,
                                                   const unsigned int dim )
{
    // see FastMemoryEfficientCellLocationinUnstructuredGridsForVisualization.pdf
    // around page 9

    // Paper arithmetic is over-optimized.. this is safer.
    const double min    = interval.bMin[dim];
    const double length = ( interval.bMax[dim] - min ) / ( num_splits + 1 );
    const double center = ( ( box.bMax[dim] + box.bMin[dim] ) / 2.0 ) - min;
#ifndef NDEBUG
#ifdef BVH_SHOW_INDEX
    std::cout << "[" << min << " , " << interval.max[dim] << " ]" << std::endl;
    std::cout << "[" << box.bMin[dim] << " , " << box.bMax[dim] << " ]" << std::endl;
    std::cout << "Length of bucket" << length << std::endl;
    std::cout << "Center: " << ( box.bMax[dim] + box.bMin[dim] ) / 2.0 << std::endl;
    std::cout << "Distance of center from min:  " << center << std::endl;
    std::cout << "ratio: " << center / length << std::endl;
    std::cout << "index: " << std::ceil( center / length ) - 1 << std::endl;
#endif
#endif
    unsigned int cl = std::ceil( center / length );
    return ( cl > 0 ? cl - 1 : 0 );
}

inline BVHTree::BVHTree( Interface* impl ) : Tree( impl ), splitsPerDir( 3 ), startSetHandle( 0 )
{
    boxTagName = treeName;
}

inline unsigned int BVHTree::set_interval( BoundBox& interval, std::vector< Bucket >::const_iterator begin,
                                           std::vector< Bucket >::const_iterator end ) const
{
    bool first         = true;
    unsigned int count = 0;
    for( std::vector< Bucket >::const_iterator b = begin; b != end; ++b )
    {
        const BoundBox& box = b->boundingBox;
        count += b->mySize;
        if( b->mySize != 0 )
        {
            if( first )
            {
                interval = box;
                first    = false;
            }
            else
                interval.update( box );
        }
    }
    return count;
}

inline void BVHTree::order_elements( HandleDataVec::iterator& begin, HandleDataVec::iterator& end,
                                     SplitData& data ) const
{
    for( HandleDataVec::iterator i = begin; i != end; ++i )
    {
        const int index = Bucket::bucket_index( splitsPerDir, i->myBox, data.boundingBox, data.dim );
        i->myDim        = ( index <= data.split ) ? 0 : 1;
    }
    std::sort( begin, end, HandleData_comparator() );
}

inline void BVHTree::choose_best_split( const std::vector< std::vector< SplitData > >& splits, SplitData& data ) const
{
    std::vector< SplitData > best_splits;
    for( std::vector< std::vector< SplitData > >::const_iterator i = splits.begin(); i != splits.end(); ++i )
    {
        std::vector< SplitData >::const_iterator j =
            std::min_element( ( *i ).begin(), ( *i ).end(), Split_comparator() );
        best_splits.push_back( *j );
    }
    data = *std::min_element( best_splits.begin(), best_splits.end(), Split_comparator() );
}

inline ErrorCode BVHTree::construct_element_vec( std::vector< HandleData >& handle_data_vec, const Range& elements,
                                                 BoundBox& bounding_box )
{
    std::vector< double > coordinate( 3 * CN::MAX_NODES_PER_ELEMENT );
    int num_conn;
    ErrorCode rval = MB_SUCCESS;
    std::vector< EntityHandle > storage;
    for( Range::iterator i = elements.begin(); i != elements.end(); ++i )
    {
        // TODO: not generic enough. Why dim != 3
        // Commence un-necessary deep copying.
        const EntityHandle* connect;
        rval = mbImpl->get_connectivity( *i, connect, num_conn, false, &storage );
        if( MB_SUCCESS != rval ) return rval;
        rval = mbImpl->get_coords( connect, num_conn, &coordinate[0] );
        if( MB_SUCCESS != rval ) return rval;
        BoundBox box;
        for( int j = 0; j < num_conn; j++ )
            box.update( &coordinate[3 * j] );
        if( i == elements.begin() )
            bounding_box = box;
        else
            bounding_box.update( box );
        handle_data_vec.push_back( HandleData( *i, box, 0.0 ) );
    }

    return rval;
}

inline ErrorCode BVHTree::reset_tree()
{
    return delete_tree_sets();
}

}  // namespace moab

#endif  // BVH_TREE_HPP