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From: asw@rlvd.UUCP (Antony Williams)
Newsgroups: net.graphics
Subject: Re: Wave-front ray tracing?
Message-ID: <1127@rlvd.UUCP>
Date: Thu, 6-Mar-86 14:25:34 EST
Article-I.D.: rlvd.1127
Posted: Thu Mar  6 14:25:34 1986
Date-Received: Sun, 9-Mar-86 09:27:54 EST
References: <13300001@ccvaxa>
Reply-To: asw@rlvd.UUCP (Antony Williams)
Organization: Rutherford Appleton Laboratory, Informatics Division, U.K.
Lines: 31

In article <13300001@ccvaxa> aglew@ccvaxa.UUCP writes:
>
>Query: might not wave-front type computations be more efficient? Take a
>wave-front from your light source (spherical, cylindrical, or planar)
>start it propagating, and compute its first intersection with an object.
>Parts of the wave-front will be modified - light "densities" will be changing
>all the time. You might even consider polarization effects. Of course,
>the more reflections/refractions you have, the more wave-fronts you'll have
>to handle, but some will fade away eventually.
>
>Has this been tried as an alternative to ray-tracing? Any references?
>Any overwhelming reasons why it won't work? The only thing I can see is that
>it is hard to work backwards from eye to light source.

See "3-D graphics and the Wave Theory", Hans P Moravec, CMU
    in Computer Graphics, Vol 15, No 3, August 1981.
    Proceedings of SIGGRAPH '81.

Basically, it doesn't work too well.  I have always suspected that it has to
do with the relative size of objects and the wavelength of the light wave.
The wave front must be represented at spatial resolution about equal
to the wavelength, which either gives massive arrays or small objects.
In the latter case, diffraction effects are not the same as in the real world,
with large objects and small wavelengths.

-- 
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