Method RenderPolygon

Rendering/OpenGL2/vtkOpenGLImageSliceMapper.cxx:324–442

------------------------------------------------------------------------------ Render the polygon that displays the image data

//------------------------------------------------------------------------------
// Render the polygon that displays the image data
void vtkOpenGLImageSliceMapper::RenderPolygon(
  vtkActor* actor, vtkPoints* points, const int extent[6], vtkRenderer* ren)
{
  vtkOpenGLClearErrorMacro();

  bool textured = (actor->GetTexture() != nullptr);
  vtkPolyData* poly = vtkPolyDataMapper::SafeDownCast(actor->GetMapper())->GetInput();
  vtkPoints* polyPoints = poly->GetPoints();
  if (this->GetOutputPointsPrecision() == vtkAlgorithm::DOUBLE_PRECISION)
  {
    polyPoints->SetDataTypeToDouble();
  }
  vtkCellArray* tris = poly->GetPolys();
  vtkDataArray* polyTCoords = poly->GetPointData()->GetTCoords();

  // do we need to rebuild the cell array?
  int numTris = 2;
  if (points)
  {
    numTris = (points->GetNumberOfPoints() - 2);
  }
  if (tris->GetNumberOfConnectivityIds() != 3 * numTris)
  {
    tris->Initialize();
    tris->AllocateEstimate(numTris, 3);
    // this wacky code below works for 2 and 4 triangles at least
    for (vtkIdType i = 0; i < numTris; i++)
    {
      tris->InsertNextCell(3);
      tris->InsertCellPoint(numTris + 1 - (i + 1) / 2);
      tris->InsertCellPoint(i / 2);
      tris->InsertCellPoint((i % 2 == 0) ? numTris - i / 2 : i / 2 + 1);
    }
    tris->Modified();
  }

  // now rebuild the points/tcoords as needed
  if (!points)
  {
    double coords[12], tcoords[8];
    this->MakeTextureGeometry(extent, coords, tcoords);

    polyPoints->SetNumberOfPoints(4);
    if (textured)
    {
      polyTCoords->SetNumberOfTuples(4);
    }
    for (int i = 0; i < 4; i++)
    {
      polyPoints->SetPoint(i, coords[3 * i], coords[3 * i + 1], coords[3 * i + 2]);
      if (textured)
      {
        polyTCoords->SetTuple(i, &tcoords[2 * i]);
      }
    }
    polyPoints->Modified();
    if (textured)
    {