C++ VTK Render Window not working on macOS - c++

Question

I am new to VTK. I was trying to run the code below on my macbook, however the window failed to pop up. Seems like it quit unexpectedly. Could someone tell me whats the reason???
TIA
int main(int argc, const char * argv[]) {
//cylinder
vtkSphereSource *sphere = vtkSphereSource::New();
sphere->SetPhiResolution(16);
sphere->SetThetaResolution(16);
//Shrink
vtkShrinkFilter *shrink = vtkShrinkFilter::New();
shrink->SetInputConnection(sphere->GetOutputPort());
shrink->SetShrinkFactor(0.9);
//Elevation Filter
vtkElevationFilter *colorIt = vtkElevationFilter::New();
colorIt->SetInputConnection(shrink->GetOutputPort());
colorIt->SetLowPoint(0,0,-0.5);
colorIt->SetHighPoint(0,0,0.5);
vtkPolyDataMapper *sphereMapper = vtkPolyDataMapper::New();
sphereMapper->SetInputConnection(colorIt->GetOutputPort());
vtkActor *sphereActor = vtkActor::New();
sphereActor->SetMapper(sphereMapper);
vtkRenderer *ren1 = vtkRenderer::New();
ren1->AddActor(sphereActor);
ren1->SetBackground(0.1,0.2,0.4);
vtkRenderWindow *renWin = vtkRenderWindow::New();
renWin->AddRenderer(ren1);
renWin->SetSize(300,300);
renWin->Render();
shrink->SetInputConnection(colorIt->GetOutputPort());
renWin->Render();
return 0;
}

Answer 1

What is the aim of the last two lines?
shrink->SetInputConnection(colorIt->GetOutputPort());
renWin->Render();
This creates a cyclical connection of the filters: sphere->shrink->colorIt->....(mapper, actor)->shrink again. Are you trying to shrink it twice? Then it's simpler to just use higher shrink factor. Or you want two different spheres there? Than you have to create two separate objects for them.
Also, output of vtkShrinkFilter is vtkUnstructuredGrid, not vtkPolyData, so you have to use vtkDataSetMapper instead of vtkPolyDataMapper. Your code works for me when I do this change and also delete the second shrink->SetInputConnection line.