Method BuildEdges

Filters/Hybrid/vtkImageToPolyDataFilter.cxx:807–1136

Uses clipping approach to build the polygon edges

// Uses clipping approach to build the polygon edges
int vtkImageToPolyDataFilter::BuildEdges(vtkUnsignedCharArray* vtkNotUsed(pixels), int dims[3],
  double origin[3], double spacing[3], vtkUnsignedCharArray* pointDescr, vtkPolyData* edges)
{
  double x[3];
  int i, j, edgeCount;
  vtkIdType ptId, p0, p1, p2, p3, startId, attrId, id[8], pts[4];
  vtkCellArray* edgeConn = edges->GetLines();
  vtkPoints* points = edges->GetPoints();

  // Build edges around perimeter of image. Note that the point ids
  // The first four points are the image corners and are inserted and
  // marked so that they can't be moved during smoothing.
  points->InsertPoint(0, origin);
  pointDescr->InsertValue(0, 1);

  // Keep track of the polygons that use each edge as well as associated
  // intersection points on edge (if any)
  this->EdgeTable = vtkEdgeTable::New();
  this->EdgeTable->InitEdgeInsertion(dims[0] * dims[1], 1);

  this->EdgeUseTable = vtkEdgeTable::New();
  this->EdgeUseTable->InitEdgeInsertion(dims[0] * dims[1], 1);

  this->EdgeUses = vtkIntArray::New();
  this->EdgeUses->SetNumberOfComponents(2);
  this->EdgeUses->Allocate(4 * dims[0] * dims[1], dims[0] * dims[1]);

  // Generate corner points of image
  x[0] = origin[0] + (dims[0] - 1) * spacing[0];
  x[1] = origin[1];
  x[2] = 0.0;
  points->InsertPoint(1, x);
  pointDescr->InsertValue(1, 1);

  x[0] = origin[0] + (dims[0] - 1) * spacing[0];
  x[1] = origin[1] + (dims[1] - 1) * spacing[1];
  x[2] = 0.0;
  points->InsertPoint(2, x);
  pointDescr->InsertValue(2, 1);

  x[0] = origin[0];
  x[1] = origin[1] + (dims[1] - 1) * spacing[1];
  x[2] = 0.0;
  points->InsertPoint(3, x);
  pointDescr->InsertValue(3, 1);

  // Let's create perimeter edges - bottom x edge
  startId = 0;
  x[1] = origin[1];
  for (i = 0; i < (dims[0] - 1); i++)
  {
    p0 = i;
    p1 = i + 1;
    if (this->Visited[p0] != this->Visited[p1])
    {
      x[0] = origin[0] + i * spacing[0] + 0.5 * spacing[0];
      ptId = points->InsertNextPoint(x);
      this->EdgeTable->InsertEdge(p0, p1, ptId);