Path: utzoo!utgpu!watmath!clyde!att!pacbell!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!bu-cs!encore!cloud9!cme
From: cme@cloud9.UUCP (Carl Ellison)
Newsgroups: comp.graphics
Subject: Re: raytracing in ||
Summary: TANSTAAFL
Keywords: 4 rays per pixel ????
Message-ID: <2595@cloud9.UUCP>
Date: 29 Nov 88 17:41:47 GMT
References: <9700001@datacube> <3148@uoregon.uoregon.edu> <1351@umbc3.UMD.EDU> <5548@thorin.cs.unc.edu>
Organization: Stratus Computer, Inc., Marlboro, MA
Lines: 23

In article <5548@thorin.cs.unc.edu>, brown@tyler.cs.unc.edu (Lurch) writes:
> 
> From what I understand, the way to achieve 4 rays per pixel is to sample at
> vertical resolution +1, horizontal resolution +1, and treat each ray as a
> 'corner' of each pixel, and average those values.  This is super cheap compared
> to sampling at twice vertical and horizontal.
> 


There ain't no such thing as a free lunch.

The re-use of corners for all pixels which share them turns this into
filtering AFTER sampling -- and sampling only at pixel resolution.

All the aliasing which a 1-sample per pixel image would have is carefully
preserved this way -- only the final picture (both good stuff and aliasing)
is blurred.

Have a nice day,

--Carl Ellison          ...!harvard!anvil!es!cme    (normal mail address)
                        ...!ulowell!cloud9!cme      (usenet news reading)
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