RTstruct display in Slice View

I used vtkPlanarContourToClosedSurfaceConversionRule in slicerRT to convert RTstruct to closed surface, but the display effect in my program is different from that in 3Dslicer? I want to know why, in 3DSlicer, the effect appears to be a closed surface sliced like the original image, while in my program, the effect appears to be a simple projection.

How can I achieve the same display effect as in 3Dslicer?

Do I need to execute vtkimagerereslice on polydata?