[vtkusers] How to perform intersection tests

[Elvis Dowson]

Hi,
          In the VTK Book 4th Edition, page 292, para 2, "For example,  
we can choose to define the region as a sphere centered at p. Then if  
a point or the points comprising a cell lie in the sphere, the point  
or cell is considered to be in the region surrounding p."

Could someone point me to an example which does this?

Best regards,

Elvis Dowson