小白遇到的问题是，想在鼠标对actor控制的时候返回camera的位置信息，各位大神能不能帮帮忙~
callback函数该怎么写？？？

static void CameraModifiedCallback(
vtkObject* caller,
long unsigned int vtkNotUsed(eventId),
void* vtkNotUsed(clientData),
void* vtkNotUsed(callData) )
{
std::cout << caller->GetClassName() << " modified" << std::endl;
vtkCamera* camera = static_cast<vtkCamera*>(caller); // print the interesting stuff
std::cout << "\tPosition: "
<< camera->GetPosition()[0] << ", "
<< camera->GetPosition()[1] << ", "
<< camera->GetPosition()[2] << std::endl;
std::cout << "\tFocal point: "
<< camera->GetFocalPoint()[0] << ", "
<< camera->GetFocalPoint()[1] << ", "
<< camera->GetFocalPoint()[2] << std::endl;
}