关于vtk HedgeHog算法的一个问题请教一下各位大佬

在官网找的一个example，原网址链接https://www.vtk.org/Wiki/VTK/Examples/Cxx/Visualization/HedgeHog
它里面的函数void CreateData(vtkStructuredGrid* sgrid)我看不明白是什么意思，谁能帮我讲解一下，代码如下，谢谢啦！

void CreateData(vtkStructuredGrid* sgrid)

{

  int i, j, k, kOffset, jOffset, offset;

  float x[3], v[3], rMin=0.5, rMax=1.0, deltaRad, deltaZ;

  float radius, theta;

  static int dims[3]={13,11,11};

  sgrid->SetDimensions(dims);

 

  // We also create the points and vectors. The points

  // form a hemi-cylinder of data.

  vtkSmartPointer<vtkFloatArray> vectors =

    vtkSmartPointer<vtkFloatArray>::New();

  vectors->SetNumberOfComponents(3);

  vectors->SetNumberOfTuples(dims[0]*dims[1]*dims[2]);

 

  vtkSmartPointer<vtkPoints> points =

    vtkSmartPointer<vtkPoints>::New();

  points->Allocate(dims[0]*dims[1]*dims[2]);

 

  deltaZ = 2.0 / (dims[2]-1);

  deltaRad = (rMax-rMin) / (dims[1]-1);

  v[2]=0.0;

  for ( k=0; k<dims[2]; k++)

    {

    x[2] = -1.0 + k*deltaZ;

    kOffset = k * dims[0] * dims[1];

    for (j=0; j<dims[1]; j++)

      {

      radius = rMin + j*deltaRad;

      jOffset = j * dims[0];

      for (i=0; i<dims[0]; i++)

        {

        theta = i * vtkMath::RadiansFromDegrees(15.0);

        x[0] = radius * cos(theta);

        x[1] = radius * sin(theta);

        v[0] = -x[1];

        v[1] = x[0];

        offset = i + jOffset + kOffset;

        points->InsertPoint(offset,x);

        vectors->InsertTuple(offset,v);

        }

      }

    }

  sgrid->SetPoints(points);

 

  sgrid->GetPointData()->SetVectors(vectors);

}