Make Region Generation based on a STL actor

I want to make region growth like as like the following image…I want to exclude the portion of the hollow region of the sleeve STL for the region growing and

image

and I would be like to clip the some portions exactly as per picture given below by considering the sleeve stl and the vtkBox for the clipping operation…

How can able to consider these operations using VTK 8.2 with cpp…Currently I done region growing using vtkCleanPolyData(input polydata as STLactor and loop as contourwidget) to clipping procedure for region growing…Now I want to thicken the region grown area and clip some of the portions as accurate…Which is the best choice for that…vtkpolydata / mesh or any other methods…

and the region growing should be filled the entire region where I drawn the contour except the inner hollow portions of the STL sleeve [Here I used to introduced a cylinder to remove the region by considering the radius of sleeve…But I cannot able to remove those portions properly…]

I have to improve the requirement…I am looking for guidance on how to proceed with this development, as I am new to this area. Your support in helping me achieve this would be greatly appreciated. I’m currently using VTK 8.2 and C++ for this task.