DivideAndConquer.cpp

// Gmsh - Copyright (C) 1997-2010 C. Geuzaine, J.-F. Remacle
//
// See the LICENSE.txt file for license information. Please report all
// issues on https://gitlab.onelab.info/gmsh/gmsh/issues.

// Triangulation using a divide and conquer algorithm
//
// The main idea is to be able to merge two Delaunay triangulations
// into a single one (see the 'Merge' function). Points are then
// separated into two groups, then each group into two, ... until
// having 1, 2 or 3 points (the triangulation is then trivial).
//
// This is used to contruct the initial mesh.
//
// Warning: point positions must be PERTURBED by a small random
// value to avoid 3 aligned points or 4 cocyclical points!

#include "GmshMessage.h"
#include "DivideAndConquer.h"
#include "Numeric.h"
#include "robustPredicates.h"
#include "BackgroundMeshTools.h"
#include "OS.h"
#include "GPoint.h"
#include "GFace.h"
#include "MLine.h"

#define Pred(x) ((x)->prev)
#define Succ(x) ((x)->next)

PointNumero DocRecord::Predecessor(PointNumero a, PointNumero b)
{
  DListPeek p = points[a].adjacent;
  if(p == NULL) return -1;

  do {
    if(p->point_num == b) return Pred(p)->point_num;
    p = Pred(p);
  } while(p != points[a].adjacent);

  return -1;
}

PointNumero DocRecord::Successor(PointNumero a, PointNumero b)
{
  DListPeek p = points[a].adjacent;
  if(p == NULL) return -1;

  do {
    if(p->point_num == b) return Succ(p)->point_num;
    p = Succ(p);
  } while(p != points[a].adjacent);

  return -1;
}

int DocRecord::FixFirst(PointNumero x, PointNumero f)
{
  DListPeek p = points[x].adjacent;
  if(p == NULL) return 0;

  int out = 0;
  DListPeek copy = p;
  do {
    if(p->point_num == f) {
      points[x].adjacent = p;
      out = 1;
    }
    else
      p = p->next;