Path: utzoo!utgpu!watmath!clyde!att!rutgers!rochester!pt.cs.cmu.edu!andrew.cmu.edu!po0o+
From: po0o+@andrew.cmu.edu (Paul Andrew Olbrich)
Newsgroups: comp.graphics
Subject: Re: Village Idiot asks about Ray Tracing
Message-ID: 
Date: 6 Dec 88 17:17:05 GMT
References: <859@amethyst.ma.arizona.edu>,
	<3324@uoregon.uoregon.edu>
Organization: Carnegie Mellon
Lines: 36
In-Reply-To: <3324@uoregon.uoregon.edu>

Hi folks.

This is in reply to some of the recent ray tracing discussion.

>  I'm writing a ray tracer right now and have some experience.

I've already written a ray tracer.  And I'm a freshman at CMU!  (I love this
stuff!)

> The question is actually trickier than you might believe.  Even
> diffusely reflecting objects reflect light, hence at every point on the
> surface of an object, the illumination is a function of its own
> radiosity and the radiosity of every patch visible AFTER ANY NUMBER OF
> BOUNCES.  Hence, there is not a great way of knowing when to quit
> tracing rays.  For instance, you hit a triangle.  You need to find the
> amount of light energy reaching that triangle from EVERY direction, not
> just the direction of the reflected ray.  Techniques of MonteCarlo
> integration, distributed ray tracing, and radiosity all attempt to deal
> with this fundamental problem.

I just wanted to bring up a small point on this.  Basically what's being said
here is that every object that you're dealing with reflects light to some
degree.  This is extremely clear when you realize that if all of the objects did
not reflect light, then no light would radiate from them at all, and you
wouldn't be able to see them!

This, of course, would be a severe bummer!

---
Drew Olbrich
po0o+@andrew.cmu.edu

"You cannot depend on your eyes when your imagination is out of focus." -- Mark
Twain

"I wouldn't trust him any farther than I could spit a rat." -- Zaphod Beeblebrox