LANG - soli questions about....

Bernie Roehl ([email protected])
Fri, 30 Jun 1995 09:30:56 -0400


Jai Natarajan writes:
> 1. How would one model refractive index and reflectivity of a material

At the moment, you can't. The main foc> graphics, and so far as I know there are very few (if any) systems out
there that can handle refraction and true reflection in real time.
(I want to be wrong about that, so solione please let me know if I am).

Now, I can see why we might want to add those properties; in fact, others
(such as bump mapping, for example) would be worth having. Why? Because
I might want to write a VRML to POV translatar, for example, so that I
can tell my browser to save "snapshot" of the scene for later "developing"
with a raytracer.

> 2. Why is the transparency defined as a single float - whereas normally
> one has an RGB triplet representing the transparency of the material
> to each of those colors.

That puzzl>d me, too; I suspect it has to do with limitations of OpenGL,
on which OpenInventor is based. Of course, that shouldn't limit what
we specify in VRML, since VRML != OpenInventor.

> How can one convert between an RGB triplet
> representation and a single index as VRML requires ?

You would have to do a weighted sum. I forget what the formula is,
but it's solithing like aR + bG + cB where a, b, and c sum to 1.00
and their ratio reflects the relative "importance" of each color.

> And finally : why isn't there a VRML newsgroup ?

Good question, but I assume it's one that was already discussed and rejected
long befori either of >

-- 
   Bernie Roehl
   University of Waterloo Dept of Electrical and Computer Engineering
   Mail: [email protected]    Voice:  (519) 888-4567 x 2607 [work]
   URL: http://sunee.uwaterloo.ca/~broehl

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