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From: td@alice.UucP (Tom Duff)
Newsgroups: net.graphics
Subject: Re: Wave-front ray tracing?
Message-ID: <5076@alice.uUCp>
Date: Tue, 4-Mar-86 09:36:26 EST
Article-I.D.: alice.5076
Posted: Tue Mar  4 09:36:26 1986
Date-Received: Wed, 5-Mar-86 06:41:56 EST
References: <13300001@ccvaxa>
Organization: Bell Labs, Murray Hill
Lines: 17

There's a paper in the 1980 Siggraph proceedings by Hans Moravec of
Carnegie-Mellon University about wave-tracing.  Moravec is interested
in what we're going to do with the enormous numbers of teraflops that
will be available to us in twenty years or so.  Wave-tracing involves
large numbers of 3-dimensional Fourier transforms, all of which must
be done at a resolution comparable to the wavelength of the light
you're dealing with.  Moravec produced some tiny (64x64?) images that
took many hours (around 30-40?) of KL-10 time to produce, and looked
like nothing at all -- you could decipher the objects in the scene
if he told you what they were, but mostly you saw diffraction fringes
-- these images were, after all, only about 32 wavelengths wide.

There's no reason why it won't work, except that producing a reasonable
image would consume all the CPU cycles produced since the dawn of history.
Tracing backwards from eye to light source is no problem -- you don't do
it that way.  Moravec includes in his scene a pinhole camera object and
displays the photons that hit the camera's screen.