octree_impl.hpp

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/*
 * Copyright (c) 2010-2015:  G-CSC, Goethe University Frankfurt
 * Author: Sebastian Reiter
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 */
 
#ifndef __H__LIB_GRID__OCTREE_IMPL__
#define __H__LIB_GRID__OCTREE_IMPL__
 
#include <vector>
#include "lib_grid/lg_base.h"
#include "common/node_tree/octree.h"
 
namespace ug
{
 
//  CreateOctree
template <class TIterator>
SPOctree
CreateOctree(Grid& grid, TIterator elemsBegin, TIterator elemsEnd,
      int maxDepth, int elemThreshold, bool bLoose,
      APosition& aPos)
{
  const char* logMsgPrefix = "  CreateOctree: ";
 
  if(elemsBegin == elemsEnd)
    return node_tree::SPCollisionTreeRootNode(NULL);
 
//  access the position attachment of the grid. 
  if(!grid.has_vertex_attachment(aPos)){
    UG_LOG(logMsgPrefix << "vertex-attachment missing: aPos\n");
    return node_tree::SPCollisionTreeRootNode(NULL);
  }
  
  Grid::VertexAttachmentAccessor<APosition> aaPos(grid, aPos);
  
//  we have to attach an int-attachment to the vertices of the grid.
  AInt aInt;
  grid.attach_to_vertices(aInt);
  Grid::VertexAttachmentAccessor<AInt> aaInt(grid, aInt);
  
//  all elements have to have the same amount of vertices
  const size_t numVertices = (*elemsBegin)->num_vertices();
  
//  initialise all entries of aInt to -1
//  since we want to allow to construct an OctTree even for small subsets
//  of a grid, we only want to touch vertices that are important.
  for(TIterator iter = elemsBegin; iter != elemsEnd; ++iter){
    for(size_t i = 0; i < numVertices; ++i)
      aaInt[(*iter)->vertex(i)] = -1;
  }
  
//  create the vElems and the vPoints arrays.
  std::vector<vector3>  vPoints;
  std::vector<int>    vElems;
  std::vector<node_tree::CollisionElementID> vElemIDs;
 
/* If you want to match the indices that are referenced by the oct-trees
 * triangles with the order of the grids vertices, than you can uncomment
 * the following code. Please note, that this code is slower than the
 * original code, if only a tiny subset of the grid is sorted into the
 * tree.
int tmpCounter = 0;
for(VertexIterator iter = grid.vertices_begin(); iter != grid.vertices_end(); ++iter){
  aaInt[*iter] = tmpCounter++;
  vPoints.push_back(aaPos[*iter]);
}
*/
 
  for(TIterator iter = elemsBegin; iter != elemsEnd; ++iter){
    typename TIterator::value_type elem = *iter;
    
  //  insert the indices into vElems and build vPoints at the same time
    for(size_t i = 0; i < numVertices; ++i){
      Vertex* v = elem->vertex(i);
      if(aaInt[v] == -1){
        aaInt[v] = (int)vPoints.size();
        vPoints.push_back(aaPos[v]);
      }
      
      vElems.push_back(aaInt[v]);
    }
    
  //  insert the element-id (the pointer to the associated grid element)
    vElemIDs.push_back(elem);
  }
  
//  arrays have been created. remove obsolete attachments
  grid.detach_from_vertices(aInt);
  
//  call the octree creation algorithm
  return node_tree::CreateOctree(&vPoints.front(), vPoints.size(),
              &vElems.front(), vElems.size(), numVertices,
              &vElemIDs.front(), maxDepth, elemThreshold, bLoose);
}
 
}// end of namespace
 
#endif