Method SubdivideFromQuadric

Filters/Sources/vtkHyperTreeGridSource.cxx:1308–1513

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void vtkHyperTreeGridSource::SubdivideFromQuadric(vtkHyperTreeGrid* output,
  vtkHyperTreeGridNonOrientedCursor* cursor, unsigned int level, int treeIdx, const int idx[3],
  double origin[3], double size[3])
{
  // Get handle on point data
  vtkCellData* outData = output->GetCellData();

  // Calculate the node global index
  vtkIdType id = cursor->GetTree()->GetGlobalIndexFromLocal(cursor->GetVertexId());
  ++this->LevelBitsIndexCnt[0];

  // Compute cell origin coordinates
  double O[] = { 0., 0., 0. };
  for (unsigned int d = 0; d < this->Dimension; ++d)
  {
    O[d] = origin[d] + idx[d] * size[d];
  }

  // Iterate over all vertices
  int nPos = 0;
  int nNeg = 0;
  double sum = 0.;
  double nVert = 1 << this->Dimension;
  for (int v = 0; v < nVert; ++v)
  {
    // Transform flat index into triple
    div_t d1 = div(v, 2);
    div_t d2 = div(d1.quot, 2);

    // Compute vertex coordinates
    double pt[3];
    pt[0] = O[0] + d1.rem * size[0];
    pt[1] = O[1] + d2.rem * size[1];
    pt[2] = O[2] + d2.quot * size[2];

    // Evaluate quadric at current vertex
    double qv = this->Quadric->EvaluateFunction(pt);
    if (qv > 0)
    {
      // Found positive value at this vertex
      ++nPos;

      // Update integral
      sum += qv;
    }
    else if (qv < 0)
    {
      // Found negative value at this vertex
      ++nNeg;

      // Update integral
      sum += qv;
    }
  } // v

  // Subdivide iff quadric changes sign within cell
  bool subdivide = nPos != nVert && nNeg != nVert;