Method ReadNFacedSection

IO/EnSight/core/EnSightDataSet.cxx:2839–2943

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void EnSightDataSet::ReadNFacedSection(int& numElements, vtkUnstructuredGrid* output)
{
  vtkLogScopeFunction(TRACE);

  // Number of elements
  this->GeometryFile.ReadNumber(&numElements);

  // (optional) Element IDs
  if (this->ElementIdsListed)
  {
    this->GeometryFile.SkipNNumbers<int>(numElements);
  }

  // Number of faces per element
  std::vector<int> numFacesPerElement(numElements, 0);
  this->GeometryFile.ReadArray(numFacesPerElement.data(), numElements);

  // Read the whole block in one go
  vtkIdType totalNumFaces = std::accumulate(
    numFacesPerElement.begin(), numFacesPerElement.end(), static_cast<vtkIdType>(0));

  std::vector<int> numNodesPerFacePerElement(totalNumFaces);
  this->GeometryFile.ReadArray(numNodesPerFacePerElement.data(), totalNumFaces);

  vtkIdType totalNumNodes = std::accumulate(
    numNodesPerFacePerElement.begin(), numNodesPerFacePerElement.end(), static_cast<vtkIdType>(0));
  std::vector<int> faceNodesBuffer(totalNumNodes);

  vtkIdType offset = 0;
  for (vtkIdType i = 0; i < totalNumFaces; ++i)
  {
    this->GeometryFile.ReadArray(
      faceNodesBuffer.data() + offset, numNodesPerFacePerElement[i], true);
    offset += numNodesPerFacePerElement[i];
  }

  // Now build the actual cells
  auto cellInfo = getVTKCellType(ElementType::NFaced);

  auto numNodesInFaceIt = numNodesPerFacePerElement.begin();
  auto nodeIt = faceNodesBuffer.begin();

  // Break through all loops if numNodesInFaceIt or nodeIt reach the end of vector
  bool endReached = false;
  vtkNew<vtkCellArray> faceStream;

  for (int elemIdx = 0; elemIdx < numElements; elemIdx++)
  {
    const int numFacesInElement = numFacesPerElement[elemIdx];
    /// @note: we could save that value from the earlier "total" computation. It's not significant
    // compared to the read time though
    const vtkIdType numNodesInElement = std::accumulate(
      numNodesInFaceIt, numNodesInFaceIt + numFacesInElement, static_cast<vtkIdType>(0));

    std::vector<vtkIdType> uniqueCellIDs;
    uniqueCellIDs.reserve(numNodesInElement);

    faceStream->Reset();