Building complex geometries using simple 3d primatives

William J. Deninger (deninger@uiuc.edu)
Mon, 17 Nov 1997 14:36:03 -0600

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Hello,

I have a peculiar question concerning implementing 3d graphics =
primitives inside one another. Suppose I have a detector composed of a =
simple block of aluminum with a hole drilled in the middle. I would =
suspect we would use TBRIK of material Al and TTUBE of material VACUUM. =
How does root know which material takes precedence in a volume shared by =
two materials such as the TTUBE inside the TBRIK?

Also, suppose those two primitives shared a common origin. Is it =
possible to have both primitives referenced by the same TNode, or is it =
necessary to have a TNode duplicated? I'm guessing that in such an =
instance, one would want to combine all objects "attached" sharing a =
node to be represented by a class of type TShape. But then the question =
becomes, which virtual functions of TShape are necessary to overload in =
order to get a correct TShape behavior?

And finally, as the geometry becomes complicated I need to highlight =
certain primitives preferably without redrawing the entire detector =
geometry. Specifically, I need to mark straws in a drift chamber in =
order to aid debugging my tracking code.=20

William J. Deninger
deninger@uiuc.edu

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Hello, 
 
I have a peculiar question concerning implementing 3d graphics = primitives=20 inside one another.  Suppose I have a detector composed of a simple = block=20 of aluminum with a hole drilled in the middle.  I would suspect we = would=20 use TBRIK of material Al and TTUBE of material VACUUM.  How does = root know=20 which material takes precedence in a volume shared by two materials such = as the=20 TTUBE inside the TBRIK?
 
Also, suppose those two primitives shared a common origin. Is it = possible=20 to have both primitives referenced by the same TNode, or is it necessary = to have=20 a TNode duplicated?  I'm guessing that in such an instance, one = would want=20 to combine all objects "attached" sharing a node to be = represented by=20 a class of type TShape.  But then the question becomes, which = virtual=20 functions of TShape are necessary to overload in order to get a correct = TShape=20 behavior?
 
And finally, as the geometry becomes complicated I need to = highlight=20 certain primitives preferably without redrawing the entire detector=20 geometry.  Specifically, I need to mark straws in a drift chamber = in order=20 to aid debugging my tracking code.
 
William J. Deninger
deninger@uiuc.edu
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