Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!david
From: david@sun.uucp (David DiGiacomo)
Newsgroups: comp.graphics
Subject: Re: raytracing in || (supersampling speedup)
Message-ID: <79571@sun.uucp>
Date: 30 Nov 88 23:38:09 GMT
References: <9700001@datacube> <3148@uoregon.uoregon.edu> <1351@umbc3.UMD.EDU> <5263@cbmvax.UUCP> <5548@thorin.cs.unc.edu> <7034@watcgl.waterloo.edu>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 12

In article <7034@watcgl.waterloo.edu> awpaeth@watcgl.waterloo.edu (Alan Wm Paeth) writes:
>The technique used by Sweeney in 1984 (while here at Waterloo) compares the four
>pixel-corner rays and if they are not in close agreement subdivides the pixel.
>The recursion terminates either when the rays from the subpixel's corners are
>in close agreement or when some max depth is reached. The subpixel values are
>averaged to form the parent pixel intensity (though a more general convolution
>could be used in gathering up the subpieces).

Let me point out the obvious.  This technique is great for antialiasing
the edges of relatively large objects, but doesn't help if there are
subpixel objects (e.g. acute polygon vertices) which don't happen to cross
the pixel corners.