Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!sun-barr!ames!indri!nero!blake!uw-beaver!uoregon!tillamook!markv
From: markv@tillamook.uucp (Mark VandeWettering)
Newsgroups: comp.graphics
Subject: Re: Ray Tracing CSG objects
Keywords: Ray Tracing, Constructive Solid Geometry
Message-ID: <4810@uoregon.uoregon.edu>
Date: 3 Jun 89 04:38:08 GMT
References: <17842@versatc.UUCP>
Sender: news@uoregon.uoregon.edu
Reply-To: markv@tillamook.UUCP (Mark VandeWettering)
Organization: University of Oregon CIS Dept.
Lines: 30

In article <17842@versatc.UUCP> ritter@versatc.UUCP (Jack Ritter) writes:
>I have a question about ray tracing CSG objects.
>Given an object represented by a CGS binary tree
>(union, intersection, & difference as operators),
>I would like to ray trace it WITHOUT using
>spacial subdivision, voxels, etc.
>I would like to do it along these lines:

	Of course, spatial subdivision, voxels etc are unnecessary.
	You can perform straightforward intersections, sort the
	resulting hits, and then use boolean algebra to decide which of
	the hits is really the "closest" valid hit.

	References:

	%A Scott D. Roth
	%T Ray Casting for Modeling Solids
	%J Computer Graphics and Image Processing
	%V 18
	%N 2
	%D Feb. 1982
	%P 109-144
	%Z the other classic ray tracing paper
	%K CSG, hidden line

	I seriously advise using some sort of subdivision technique
	though.  It really isn't all that difficult, and the payoffs are
	enormous.

Mark VandeWettering