[vtkusers] Part of an actor invisible, the rest visible

[Baris Yalcin]

Hi everyone,
 
I want to implement that a part of an actor is invisible and the rest visible. 
Example:  A chair is an actor. One leg of the chair should be invisible and 
the other three legs visible. 

To implement this I use the opacity property (transparency) of the lookup 
table ( opacity=0.0-->invisible,  opacity=1.0 -->visible).
 
The problem: the transparent part is not really transparent. Non-transparent 
triangles which are occluded by fully transparent triangles are not rendered 
anymore. Instead only the background is visible in these parts of the 
visualisation.

Is it possible to organize the rendering process in a way that non-transparent 
triangles are rendered before transparent triangles? 

If somebody has any suggestions or ideas, that would be great. 
 
Thanks a lot in advance,

Baris

P.S.: In my case the rendered object is not chair, but a complex structure 
(vessel tree). You find as attachement "screenshot_vessel.jpg" which is a 
screenshot of the structure where a part of the structure is invisible.
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