Method CoverExtent

IO/Parallel/vtkPDataSetReader.cxx:1130–1230

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//------------------------------------------------------------------------------
void vtkPDataSetReader::CoverExtent(int ext[6], int* pieceMask)
{
  int bestArea;
  int area;
  int best;
  int cExt[6]; // Covered
  int rExt[6]; // Remainder piece
  int i, j;

  // Pick the piece with the largest coverage.
  // Greedy search should be good enough.
  best = -1;
  bestArea = 0;
  for (i = 0; i < this->NumberOfPieces; ++i)
  {
    // Compute coverage.
    area = 1;
    for (j = 0; j < 3; ++j)
    { // Intersection of piece and extent to cover.
      cExt[j * 2] = ext[j * 2];
      if (this->PieceExtents[i][j * 2] > ext[j * 2])
      {
        cExt[j * 2] = this->PieceExtents[i][j * 2];
      }
      cExt[j * 2 + 1] = ext[j * 2 + 1];
      if (this->PieceExtents[i][j * 2 + 1] < ext[j * 2 + 1])
      {
        cExt[j * 2 + 1] = this->PieceExtents[i][j * 2 + 1];
      }
      // Compute the area for cells.
      if (cExt[j * 2] >= cExt[j * 2 + 1])
      {
        area = 0;
      }
      else
      {
        area *= (cExt[j * 2 + 1] - cExt[j * 2]);
      }
    }
    if (area > bestArea)
    {
      bestArea = area;
      best = i;
    }
  }

  // It could happen if pieces do not have complete coverage.
  if (bestArea <= 0)
  {
    vtkErrorMacro("Incomplete coverage.");
    return;
  }

  // Mark the chosen piece in the mask.
  pieceMask[best] = 1;

  // Now recompute the coverage for the chosen piece.
  i = best;