Method ComputeRotationAndTranlation

Rendering/Annotation/vtkAxisFollower.cxx:287–349

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void vtkAxisFollower::ComputeRotationAndTranlation(vtkRenderer* ren, double translation[3],
  double rX[3], double rY[3], double rZ[3], vtkAxisActor* axis)
{
  double autoScaleHoriz =
    this->AutoScale(ren, this->Camera, this->ScreenOffsetVector[0], this->Position);
  double autoScaleVert =
    this->AutoScale(ren, this->Camera, this->ScreenOffsetVector[1], this->Position);

  double dop[3];
  this->Camera->GetDirectionOfProjection(dop);
  vtkMath::Normalize(dop);

  this->CalculateOrthogonalVectors(rX, rY, rZ, axis, dop, ren);

  double dotVal = vtkMath::Dot(rZ, dop);

  double origRx[3] = { rX[0], rX[1], rX[2] };
  double origRy[3] = { rY[0], rY[1], rY[2] };

  // NOTE: Basically the idea here is that dotVal will be positive
  // only when we have projection direction aligned with our z direction
  // and when that happens it means that our Y is inverted.
  if (dotVal > 0)
  {
    rY[0] = -rY[0];
    rY[1] = -rY[1];
    rY[2] = -rY[2];
  }

  // Check visibility at current view angle.
  if (this->EnableViewAngleLOD)
  {
    this->ExecuteViewAngleVisibility(rZ);
  }
  else
  {
    this->VisibleAtCurrentViewAngle = 1;
  }

  // Since we already stored all the possible Y axes that are geometry aligned,
  // we compare our vertical vector with these vectors and if it aligns then we
  // translate in opposite direction.
  int axisPosition = this->Axis->GetAxisPosition();
  int vertSign;
  double vertDotVal1 =
    vtkMath::Dot(AxisAlignedY[this->Axis->GetAxisType()][axisPosition][0], origRy);
  double vertDotVal2 =
    vtkMath::Dot(AxisAlignedY[this->Axis->GetAxisType()][axisPosition][1], origRy);

  if (fabs(vertDotVal1) > fabs(vertDotVal2))
  {
    vertSign = (vertDotVal1 > 0 ? -1 : 1);
  }
  else
  {
    vertSign = (vertDotVal2 > 0 ? -1 : 1);
  }