Method ComputeNormals

Common/DataModel/vtkPolyPlane.cxx:73–129

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//------------------------------------------------------------------------------
void vtkPolyPlane::ComputeNormals()
{
  if (!this->PolyLine)
  {
    return;
  }

  if (this->GetMTime() > this->NormalComputeTime.GetMTime())
  {
    // Recompute the normal array.

    if (this->Normals)
    {
      // Delete the array if it already exists. We will reallocate later.
      this->Normals->Delete();
      this->Normals = nullptr;
    }

    vtkPoints* points = this->PolyLine->GetPoints();
    const vtkIdType nPoints = points->GetNumberOfPoints();
    const vtkIdType nLines = nPoints - 1;

    // Allocate an array to store the normals

    this->Normals = vtkDoubleArray::New();
    this->Normals->SetNumberOfComponents(3);
    this->Normals->Allocate(3 * nLines);
    this->Normals->SetName("Normals");
    this->Normals->SetNumberOfTuples(nLines);

    // Now iterate through all the lines and compute normal of each plane
    // in the polyplane.

    double v1[3], p[3], n[3];

    for (int pIdx = 0; pIdx < nLines; ++pIdx)
    {
      // Compute the plane normal for this segment by taking the cross product
      // of the line direction and the extrusion direction.

      points->GetPoint(pIdx, p);
      points->GetPoint(pIdx + 1, v1);

      // The line direction vector
      v1[0] -= p[0];
      v1[1] -= p[1];
      v1[2] -= p[2];

      // 'n' is the computed normal.
      vtkMath::Cross(v1, this->ExtrusionDirection, n);
      vtkMath::Normalize(n);

      // Store the normal in our array.
      this->Normals->SetTuple(pIdx, n);
    }
  }
}