Method Is3DComputeParameters

IO/SegY/vtkSegYReaderInternal.cxx:108–285

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//------------------------------------------------------------------------------
bool vtkSegYReaderInternal::Is3DComputeParameters(
  int* extent, double origin[3], double spacing[3][3], int* spacingSign, bool force2D)
{
  this->ReadHeader();
  std::streamoff traceStartPos = FIRST_TRACE_START_POS;
  std::streamoff fileSize = vtkSegYIOUtils::Instance()->getFileSize(this->In);
  int inlineNumber = 0, crosslineNumber;
  int xCoord = 0, yCoord = 0;
  short coordMultiplier = 0;

  size_t traceCount = 0;

  // for the forced 2D case we ignore lines/crosslines and just stitch together the
  // traces in order applying their x,y coordinates
  if (force2D)
  {
    while (traceStartPos + 240 < fileSize)
    {
      this->TraceReader->ReadInlineCrossline(traceStartPos, this->In, this->FormatCode,
        &inlineNumber, &crosslineNumber, &xCoord, &yCoord, &coordMultiplier);
      traceCount++;
    }
    extent[0] = 0;
    extent[1] = static_cast<int>(traceCount - 1);
    extent[2] = 0;
    extent[3] = 0;
    extent[4] = 0;
    extent[5] = this->SampleCountPerTrace - 1;
    return false;
  }

  // compute the dimensions of the dataset, to be safe we
  // look at all the traces and compute the set of inline
  // and crossline indices
  std::set<int> crossLines;
  std::map<int, std::array<double, 3>> crossCoordinates;
  std::set<int> inLines;
  int basisPointCount = 0;
  double basisCoords[3][3];
  int basisIndex[3][2] = { { 0, 0 }, { 0, 0 }, { 0, 0 } };
  double iBasis[2][3];
  double basisLength[2];

  while (traceStartPos + 240 < fileSize)
  {
    this->TraceReader->ReadInlineCrossline(traceStartPos, this->In, this->FormatCode, &inlineNumber,
      &crosslineNumber, &xCoord, &yCoord, &coordMultiplier);
    traceCount++;
    double coordinateMultiplier = decodeMultiplier(coordMultiplier);

    // store a third point, must have different basis from
    // first two
    if (basisPointCount == 2)
    {
      iBasis[1][0] = crosslineNumber - basisIndex[0][0];
      iBasis[1][1] = inlineNumber - basisIndex[0][1];
      iBasis[1][2] = 0.0;
      basisLength[1] = vtkMath::Normalize(iBasis[1]);