Method BuildTicksPolyData

Rendering/Annotation/vtkAxisActor2D.cxx:678–757

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void vtkAxisActor2D::BuildTicksPolyData(vtkViewport* viewport)
{
  this->Axis->Initialize();

  vtkNew<vtkPoints> pts;
  vtkNew<vtkCellArray> lines;
  this->Axis->SetPoints(pts);
  this->Axis->SetLines(lines);

  // Generate the axis and tick marks.
  // We'll do our computation in viewport coordinates. First determine the
  // location of the endpoints.
  int* x = this->PositionCoordinate->GetComputedViewportValue(viewport);
  double axisStart[3];
  axisStart[0] = x[0];
  axisStart[1] = x[1];
  axisStart[2] = 0.0;

  x = this->Position2Coordinate->GetComputedViewportValue(viewport);
  double axisEnd[3];
  axisEnd[0] = x[0];
  axisEnd[1] = x[1];
  axisEnd[2] = 0.0;

  // axis extremity
  vtkIdType axisPoints[2];
  axisPoints[0] = pts->InsertNextPoint(axisStart);
  // Generate point along axis (as well as tick points)
  double theta = this->GetAxisAngle(viewport);

  double normalizedAxis[3];
  vtkMath::Subtract(axisEnd, axisStart, normalizedAxis);
  double axisLength = vtkMath::Normalize(normalizedAxis);

  int totalNumberOfTicks = static_cast<int>(this->NormalizedTickPositions.size());

  this->TicksStartPos->SetNumberOfPoints(totalNumberOfTicks);

  for (int tick = 0; tick < totalNumberOfTicks; tick++)
  {
    int tickLength = 0;
    if (tick % (this->NumberOfMinorTicks + 1) == 0)
    {
      tickLength = this->TickLength;
    }
    else
    {
      tickLength = this->MinorTickLength;
    }

    double tickPos[3];
    tickPos[2] = 0;
    tickPos[0] =
      axisStart[0] + this->NormalizedTickPositions[tick] * normalizedAxis[0] * axisLength;
    tickPos[1] =
      axisStart[1] + this->NormalizedTickPositions[tick] * normalizedAxis[1] * axisLength;
    this->TicksStartPos->SetPoint(tick, tickPos);