pcl+vtk（十五）vtkInteractorStyleTrackballCamera用户交互

一、vtkInteractorStyleTrackballCamera介绍

vtkInteractorStyleTrackballCamera控制用户交互操作相机，场景的视点。在该类及其子类中，移动的是Camera，Actor并没有发生移动。

主要鼠标键盘操作控制：

左键按住移动：旋转

右键按住移动：缩放

滚轮按住移动：移动

ctrl +左键按住移动：快速旋转（同旋转不同）

shift +左键按住移动：移动

ctrl + shift +左键按住移动：缩放

二、鼠标事件

如果有鼠标事件处理等相应的需求，可以重写该事件。

  void OnMouseMove() override; //鼠标移动事件
  void OnLeftButtonDown() override;//左键按下事件
  void OnLeftButtonUp() override;//左键抬起事件
  void OnMiddleButtonDown() override;//滚轮按下事件
  void OnMiddleButtonUp() override;//滚轮抬起事件
  void OnRightButtonDown() override;//右键按下事件
  void OnRightButtonUp() override;//右键抬起事件
  void OnMouseWheelForward() override;//滚轮向前事件
  void OnMouseWheelBackward() override;//滚轮向后事件

具体事件的实现，可以查看vtk的源码查看，下面只列举几个：

void OnLeftButtonDown() override;//左键按下事件

void vtkInteractorStyleTrackballCamera::OnLeftButtonDown()
{
  this->FindPokedRenderer(this->Interactor->GetEventPosition()[0],
                          this->Interactor->GetEventPosition()[1]);
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  this->GrabFocus(this->EventCallbackCommand);
  if (this->Interactor->GetShiftKey())
  {
    if (this->Interactor->GetControlKey())
    {
      this->StartDolly();
    }
    else
    {
      this->StartPan();
    }
  }
  else
  {
    if (this->Interactor->GetControlKey())
    {
      this->StartSpin();
    }
    else
    {
      this->StartRotate();
    }
  }
}

void OnMouseWheelForward() override;//滚轮向前事件

void vtkInteractorStyleTrackballCamera::OnMouseWheelForward()
{
  this->FindPokedRenderer(this->Interactor->GetEventPosition()[0],
                          this->Interactor->GetEventPosition()[1]);
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  this->GrabFocus(this->EventCallbackCommand);
  this->StartDolly();
  double factor = this->MotionFactor * 0.2 * this->MouseWheelMotionFactor;
  this->Dolly(pow(1.1, factor));
  this->EndDolly();
  this->ReleaseFocus();
}

 三、旋转平移缩放等事件

  void Rotate() override;//旋转
  void Spin() override;//快速旋转
  void Pan() override;//平移
  void Dolly() override;//缩放

函数实现的源码如下：

void Rotate() override;//旋转

void vtkInteractorStyleTrackballCamera::Rotate()
{
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  vtkRenderWindowInteractor *rwi = this->Interactor;

  int dx = rwi->GetEventPosition()[0] - rwi->GetLastEventPosition()[0];
  int dy = rwi->GetEventPosition()[1] - rwi->GetLastEventPosition()[1];

  int *size = this->CurrentRenderer->GetRenderWindow()->GetSize();

  double delta_elevation = -20.0 / size[1];
  double delta_azimuth = -20.0 / size[0];

  double rxf = dx * delta_azimuth * this->MotionFactor;
  double ryf = dy * delta_elevation * this->MotionFactor;

  vtkCamera *camera = this->CurrentRenderer->GetActiveCamera();
  camera->Azimuth(rxf);
  camera->Elevation(ryf);
  camera->OrthogonalizeViewUp();

  if (this->AutoAdjustCameraClippingRange)
  {
    this->CurrentRenderer->ResetCameraClippingRange();
  }

  if (rwi->GetLightFollowCamera())
  {
    this->CurrentRenderer->UpdateLightsGeometryToFollowCamera();
  }

  rwi->Render();
}

  void Spin() override;//快速旋转

void vtkInteractorStyleTrackballCamera::Spin()
{
  if ( this->CurrentRenderer == nullptr )
  {
    return;
  }

  vtkRenderWindowInteractor *rwi = this->Interactor;

  double *center = this->CurrentRenderer->GetCenter();

  double newAngle =
    vtkMath::DegreesFromRadians( atan2( rwi->GetEventPosition()[1] - center[1],
                                        rwi->GetEventPosition()[0] - center[0] ) );

  double oldAngle =
    vtkMath::DegreesFromRadians( atan2( rwi->GetLastEventPosition()[1] - center[1],
                                        rwi->GetLastEventPosition()[0] - center[0] ) );

  vtkCamera *camera = this->CurrentRenderer->GetActiveCamera();
  camera->Roll( newAngle - oldAngle );
  camera->OrthogonalizeViewUp();

  rwi->Render();
}

  void Pan() override;//平移

void vtkInteractorStyleTrackballCamera::Pan()
{
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  vtkRenderWindowInteractor *rwi = this->Interactor;

  double viewFocus[4], focalDepth, viewPoint[3];
  double newPickPoint[4], oldPickPoint[4], motionVector[3];

  // Calculate the focal depth since we'll be using it a lot

  vtkCamera *camera = this->CurrentRenderer->GetActiveCamera();
  camera->GetFocalPoint(viewFocus);
  this->ComputeWorldToDisplay(viewFocus[0], viewFocus[1], viewFocus[2],
                              viewFocus);
  focalDepth = viewFocus[2];

  this->ComputeDisplayToWorld(rwi->GetEventPosition()[0],
                              rwi->GetEventPosition()[1],
                              focalDepth,
                              newPickPoint);

  // Has to recalc old mouse point since the viewport has moved,
  // so can't move it outside the loop

  this->ComputeDisplayToWorld(rwi->GetLastEventPosition()[0],
                              rwi->GetLastEventPosition()[1],
                              focalDepth,
                              oldPickPoint);

  // Camera motion is reversed

  motionVector[0] = oldPickPoint[0] - newPickPoint[0];
  motionVector[1] = oldPickPoint[1] - newPickPoint[1];
  motionVector[2] = oldPickPoint[2] - newPickPoint[2];

  camera->GetFocalPoint(viewFocus);
  camera->GetPosition(viewPoint);
  camera->SetFocalPoint(motionVector[0] + viewFocus[0],
                        motionVector[1] + viewFocus[1],
                        motionVector[2] + viewFocus[2]);

  camera->SetPosition(motionVector[0] + viewPoint[0],
                      motionVector[1] + viewPoint[1],
                      motionVector[2] + viewPoint[2]);

  if (rwi->GetLightFollowCamera())
  {
    this->CurrentRenderer->UpdateLightsGeometryToFollowCamera();
  }

  rwi->Render();
}

  void Dolly() override;//缩放

void vtkInteractorStyleTrackballCamera::Dolly()
{
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  vtkRenderWindowInteractor *rwi = this->Interactor;
  double *center = this->CurrentRenderer->GetCenter();
  int dy = rwi->GetEventPosition()[1] - rwi->GetLastEventPosition()[1];
  double dyf = this->MotionFactor * dy / center[1];
  this->Dolly(pow(1.1, dyf));
}

void vtkInteractorStyleTrackballCamera::Dolly(double factor)
{
  if (this->CurrentRenderer == nullptr)
  {
    return;
  }

  vtkCamera *camera = this->CurrentRenderer->GetActiveCamera();
  if (camera->GetParallelProjection())
  {
    camera->SetParallelScale(camera->GetParallelScale() / factor);
  }
  else
  {
    camera->Dolly(factor);
    if (this->AutoAdjustCameraClippingRange)
    {
      this->CurrentRenderer->ResetCameraClippingRange();
    }
  }

  if (this->Interactor->GetLightFollowCamera())
  {
    this->CurrentRenderer->UpdateLightsGeometryToFollowCamera();
  }

  this->Interactor->Render();
}