Path: utzoo!attcan!uunet!sco!brianm
From: brianm@sco.COM (Brian Moffet)
Newsgroups: comp.graphics
Subject: ray tracing transparent images and color
Keywords: color transparent raytracing
Message-ID: <2809@scolex.sco.COM>
Date: 1 Jun 89 17:14:35 GMT
Organization: The Santa Cruz Operation, Inc.
Lines: 42

Hi, me again

Just a quick (hah!) question regarding percieved color.
I was doing some thought experiments on how one would
do a ray trace of a transparent object.   Ignore everything
except tint of the object.  So, no refraction or reflection 
involved.

I am going to work in a simple color scheme, where colors
will be defined as scales of red-green-blue with 0 being
lowest (ie off) and 16 being highest.

Given an object whose tint is { 2, 0, 4 } (r,g,b)  in front of
a background whose solid color is { 14, 15, 10 }.
So, a different color will be shown for the object due to the
interaction of the transparent object and the solid background.
I also assume that the color will tend toward black.

Given this, I would say that I can take the two objects and combine them
in the following equation:

	Rfinal = Rback - Gobject - Bobject
	Gfinal = GBack - Robject - Bobject
	Bfinal = Bback - Gobject - Robject

for a final shown color of  { 10, 9, 8 }.

The reason I think this wa is it does produce blak on opposing colors
like red object and blue background.

Does this make sense?  Any good references?

thanks.

brian moffet

Please excuse spelling errors, This machine doesn't have spell!
-- 
Brian Moffet			{uunet,decvax!microsoft,ucscc}!sco!brianm
 -or-				...sco!alar!brian
"I was everything you wanted me to be.  You were afraid, I was frightening."
My fish and company have policies.  I have opinions.