Add a force2d option for segy

Add option to force interpretation of segy file as a 2d sheet
producing structured grid.

IO/SegY/vtkSegYReader.cxx

@@ -37,6 +37,7 @@ vtkSegYReader::vtkSegYReader()
   this->Reader = new vtkSegYReaderInternal();
   this->FileName = nullptr;
   this->Is3D = false;
+  this->Force2D = false;
   std::fill(this->DataOrigin, this->DataOrigin + 3, 0.0);
   std::fill(this->DataSpacing[0], this->DataSpacing[0] + 3, 1.0);
   std::fill(this->DataSpacing[1], this->DataSpacing[1] + 3, 1.0);
@@ -190,7 +191,7 @@ int vtkSegYReader::RequestDataObject(vtkInformation*,
     return 0;
   }
   this->Is3D = this->Reader->Is3DComputeParameters(
-    this->DataExtent, this->DataOrigin, this->DataSpacing, this->DataSpacingSign);
+    this->DataExtent, this->DataOrigin, this->DataSpacing, this->DataSpacingSign, this->Force2D);
   const char* outputTypeName =
     (this->Is3D && !this->StructuredGrid) ? "vtkImageData" : "vtkStructuredGrid";
 

IO/SegY/vtkSegYReader.h

@@ -119,6 +119,19 @@ public:
   vtkBooleanMacro(StructuredGrid, int);
   //@}
 
+  //@{
+  /**
+   * Should we force the data to be interpreted as a 2D dataset? It may be a
+   * 2D sheet through 3D space. When this is turned on we ignore the cross
+   * line and line values and instead build a 2D data by processing and
+   * connecting the traces in order from first to last. The output will be a
+   * Structrured Grid.
+   */
+  vtkSetMacro(Force2D, bool);
+  vtkGetMacro(Force2D, bool);
+  vtkBooleanMacro(Force2D, bool);
+  //@}
+
 protected:
   int RequestData(vtkInformation* request, vtkInformationVector** inputVector,
     vtkInformationVector* outputVector) override;
@@ -146,6 +159,8 @@ protected:
 
   int VerticalCRS;
 
+  bool Force2D;
+
 private:
   vtkSegYReader(const vtkSegYReader&) = delete;
   void operator=(const vtkSegYReader&) = delete;

IO/SegY/vtkSegYReaderInternal.cxx

@@ -40,7 +40,6 @@ double decodeMultiplier(short multiplier)
 {
   return (multiplier < 0) ? (-1.0 / multiplier) : (multiplier > 0 ? multiplier : 1.0);
 }
-
 };
 
 //-----------------------------------------------------------------------------
@@ -117,7 +116,7 @@ bool vtkSegYReaderInternal::ReadHeader()
 
 //-----------------------------------------------------------------------------
 bool vtkSegYReaderInternal::Is3DComputeParameters(
-  int* extent, double origin[3], double spacing[3][3], int* spacingSign)
+  int* extent, double origin[3], double spacing[3][3], int* spacingSign, bool force2D)
 {
   this->ReadHeader();
   std::streamoff traceStartPos = FIRST_TRACE_START_POS;
@@ -126,19 +125,39 @@ bool vtkSegYReaderInternal::Is3DComputeParameters(
   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 indicies
   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];
-  size_t traceCount = 0;
+
   while (traceStartPos + 240 < fileSize)
   {
     this->TraceReader->ReadInlineCrossline(traceStartPos, this->In, this->FormatCode, &inlineNumber,

IO/SegY/vtkSegYReaderInternal.h

@@ -37,7 +37,8 @@ public:
   ~vtkSegYReaderInternal();
 
 public:
-  bool Is3DComputeParameters(int* extent, double origin[3], double spacing[3][3], int* spacingSign);
+  bool Is3DComputeParameters(
+    int* extent, double origin[3], double spacing[3][3], int* spacingSign, bool force2D);
   void LoadTraces(int* extent);
 
   void ExportData(