[vtkusers] cylinder + vtkPerspectiveTransform -> truncated cone

[Gib Bogle]

In my application I want to visualize a vessel network made of a large number 
(order of 100k) of segments of tube, each segment being a truncated cone, i.e. 
the diameter varies along the segment.  Searching for a way to make a truncated 
cone, I saw a suggestion for making it from a cylinder, using 
vtkPerspectiveTransform. I would appreciate some guidance on how to go about 
this.  Because I'm rendering  a large number of these segments, I'd like to do 
it as fast as possible.  Is there an example relevant to this task?

Thanks
Gib