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From: woolstar@nntp-server.caltech.edu (John D. Woolverton)
Newsgroups: comp.graphics
Subject: Trying to get soft shadows
Summary: My pictures are noisy, help
Keywords: ray tracing shadows soft areas lights
Message-ID: <1991Mar20.104448.3681@nntp-server.caltech.edu>
Date: 20 Mar 91 10:44:48 GMT
Organization: California Institute of Technology, Pasadena
Lines: 24


   By popular request from my users, I added soft shadows
to my ray tracing package, the easiest way I knew how.
To evaluate an area light source, I shoot <n> rays at a
point randomly picked inside a sphere of radius <r> 
about the location of the light.
   The number of rays <n> and the radius of the light <r>
are both user selectable.

   Currently with r=20.0 and n=64, I get a fairly nice
soft shadow, except there is a low level of noise.
I figure I could get rid of it by bumping up n to about 500,
but I don't have that much patience.

   Could anyone suggest any open solutions (ie. ones that
I could implement without oweing royalties, I heard that
the Pixar noise algo. was patented.)
   The other avenue I'm looking at is trying to come up
with some post-process filter that will remove the noise, 
without taking away too much sharpness.
   Kind of a VHS-HQ circuit for my ray tracer.  :-)

	John D. Woolverton, Video Bits
	woolstar@cobalt.caltech.edu