c++写一个动态库，可以调用动态库里面的函数生产stl文件，这个具体思路是咋样的啊

vtkSTLReader part = vtkSTLReader::New();
/*part->SetOutput(part->GetOutput());/

if (G == 1) part->SetFileName("standard_ankle.stl");
else if (G == 2) part->SetFileName("standard_elbow.stl");
else if (G == 3) part->SetFileName("standard_wrist.stl");
else if (G == 4) part->SetFileName("standard_wrist_st.stl");
part->Update();

//vtkPolyData *pd = part->GetOutput();
//
vtkSphereSource *sphere = vtkSphereSource::New();
sphere->SetThetaResolution(12);
sphere->SetPhiResolution(12);

vtkPolyDataMapper *mapper = vtkPolyDataMapper::New();
//mapper->SetInputData(pd);
mapper->SetInputConnection(part->GetOutputPort());





vtkActor *va = vtkActor::New();
va->SetMapper(mapper);

vtkRenderer *a = vtkRenderer::New();
//vtkRenderWindow *b =vtkRenderWindow::New();
//b->AddRenderer(a);
a->AddActor(va);
a->SetBackground(.3, .6, .3);

怎么写才能调用这个a呀

https://blog.csdn.net/zhangfuliang123/article/details/71515796