vtkOrientationMarkerWidget在Qt窗口中不显示

VTKWidget继承自QVTKRenderWidget

解决方法：

1. 注意this->setRenderWindow(renderWindow);和this->renderWindow()->AddRenderer(renderer);以及omw->EnabledOn();代码段的位置
2. vtkOrientationMarkerWidget不要使用智能指针，出了作用域会被析构

VTKWidget::VTKWidget()
{
        vtkNew colors;

	vtkNew renderWindow;
	this->setRenderWindow(renderWindow);

	vtkNew style;
	this->interactor()->SetInteractorStyle(style);

	// Sphere
	vtkNew sphereSource;
	sphereSource->Update();
	vtkNew sphereMapper;
	sphereMapper->SetInputConnection(sphereSource->GetOutputPort());
	vtkNew sphereActor;
	sphereActor->SetMapper(sphereMapper);
	sphereActor->GetProperty()->SetColor(colors->GetColor4d("Tomato").GetData());

	// VTK Renderer
	vtkNew renderer;
	renderer->AddActor(sphereActor);
	renderer->SetBackground(colors->GetColor3d("SteelBlue").GetData());
	renderer->ResetCamera();

	// Connect VTK with Qt
	this->renderWindow()->AddRenderer(renderer);

	std::array scale{ {1.0, 1.0, 1.0} };

	vtkAxesActor* axes = vtkAxesActor::New();
	axes->SetScale(1,1,1);
	axes->SetShaftTypeToCylinder();

	axes->SetCylinderRadius(0.5 * axes->GetCylinderRadius());  //轴的粗细
	axes->SetConeRadius(1.025 * axes->GetConeRadius());        //圆锥的大小
	axes->SetSphereRadius(1.5 * axes->GetSphereRadius());

	vtkTextProperty* tprop = axes->GetXAxisCaptionActor2D()->GetCaptionTextProperty();
	tprop->ItalicOn();  //启用文本斜体
	tprop->ShadowOn();  //启用文本阴影
	tprop->SetFontFamilyToTimes();  //字体
	tprop->SetColor(1, 1, 1);  //标签文字颜色

	axes->GetYAxisCaptionActor2D()->GetCaptionTextProperty()->ShallowCopy(tprop);
	axes->GetZAxisCaptionActor2D()->GetCaptionTextProperty()->ShallowCopy(tprop);

	vtkOrientationMarkerWidget* omw = vtkOrientationMarkerWidget::New();
	omw->SetOrientationMarker(axes);
	omw->SetViewport(0.8, 0, 1.0, 0.2);
	omw->SetOutlineColor(1, 0, 0);
	omw->SetInteractor(this->interactor());
	omw->EnabledOn();
	omw->InteractiveOn();
}