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From: bungi@milton.u.washington.edu (Timothy J. Wood)
Newsgroups: alt.fractals,sci.math,comp.graphics
Subject: Re: 3-d fractal raytracer?
Message-ID: <1991May3.183504.12985@milton.u.washington.edu>
Date: 3 May 91 18:35:04 GMT
References: <1991Apr30.074427.29894@milton.u.washington.edu> <1991May3.085302.18527@zorch.SF-Bay.ORG>
Organization: University of Washington, Seattle
Lines: 25

In article <1991May3.085302.18527@zorch.SF-Bay.ORG> xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) writes:
>> bungi@u.washington.edu writes:
>
>> Failing this, does anyone know a fairly accurate method for computing
>> the a normal to a procedurally defined surface (in this case M or
>> J_c)?
>
>... what in the
>world does one intend when one says the "normal" to such an object at a
>particular point?
>
>Does one limit resolution, do some local smoothing, and take the normal
>to the resultant bounding surface?
>

  The method i'm using is an approximation based on the gradient of the
distance estimator function d(z) presented in 'The Science of Fractal
Images' (Peitgen).  One can also use the gradient of the potential function
G(z) (from the same source).


-- 
-------------------------------------------------------------------------------
        Timothy Wood : bungi@u.washington.edu, tjwood@cs.washington.edu
                   ... alice everyday brings sunshine ...