Function AreAllFacesPlanar

Filters/HyperTree/vtkHyperTreeGridContour.cxx:67–112

Return true if all faces of the cell are planar. The cell is expected to be a vtkVoxel instance.

// Return true if all faces of the cell are planar.
// The cell is expected to be a vtkVoxel instance.
bool AreAllFacesPlanar(vtkCell* cell)
{
  bool allFacesArePlanar = true;

  std::array<std::array<double, 3>, POLY_FACES_POINTS_NB> facePoints{};

  // For each face
  for (int faceId = 0, canonicalId = 0; faceId < ::POLY_FACES_NB; faceId++)
  {
    // Retrieve face points
    for (int i = 0; i < ::POLY_FACES_POINTS_NB; i++, canonicalId++)
    {
      auto point = cell->GetPoints()->GetPoint(::CANONICAL_FACES[canonicalId]);
      facePoints[i][0] = point[0];
      facePoints[i][1] = point[1];
      facePoints[i][2] = point[2];
    }

    // Test if 3 vectors of the face are coplanar
    std::array<double, 3> v1{};
    v1[0] = facePoints[1][0] - facePoints[0][0];
    v1[1] = facePoints[1][1] - facePoints[0][1];
    v1[2] = facePoints[1][2] - facePoints[0][2];

    std::array<double, 3> v2{};
    v2[0] = facePoints[2][0] - facePoints[0][0];
    v2[1] = facePoints[2][1] - facePoints[0][1];
    v2[2] = facePoints[2][2] - facePoints[0][2];

    std::array<double, 3> v3{};
    v3[0] = facePoints[3][0] - facePoints[0][0];
    v3[1] = facePoints[3][1] - facePoints[0][1];
    v3[2] = facePoints[3][2] - facePoints[0][2];

    double cross[3] = { 0. };
    vtkMath::Cross(v1, v2, cross);

    if (!vtkMathUtilities::FuzzyCompare(vtkMath::Dot(cross, v3), 0.))
    {
      allFacesArePlanar = false;
      break;
    }
  }

  return allFacesArePlanar;
}

// Given contour values, find a "valid" epsilon value, allowing to discriminate values
// by fuzzy comparison. Returned espilon correspond to the min difference between contour