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From: uselton@nas.nasa.gov (Samuel P. Uselton)
Newsgroups: comp.graphics.visualization
Subject: Re: surface rendering of fuzzy cloud
Summary: Further amendment
Message-ID: <1991May2.175729.28485@nas.nasa.gov>
Date: 2 May 91 17:57:29 GMT
References: <2594@amethyst.math.arizona.edu> <73521@eerie.acsu.Buffalo.EDU> <1991Apr30.182711.2223@fido.wpd.sgi.com> <74189@eerie.acsu.Buffalo.EDU>
Sender: Sam Uselton
Distribution: usa
Organization: NAS Program, NASA Ames Research Center, Moffett Field, CA
Lines: 41

In article <74189@eerie.acsu.Buffalo.EDU> okeefe@cs.Buffalo.EDU (Paul O'Keefe) writes:
>
>|> In article <73521@eerie.acsu.Buffalo.EDU>, okeefe@cs.Buffalo.EDU (Paul O'Keefe) writes:
>|>
>|> Mark LeVoy of UNC/Chapel Hill has an iso-value surface rendering algorithm
>|> which is detailed in his widely cited article,
>|> "The Display of Surfaces from Volume Data", IEEE CG&A, May 1988.
>
>A few amendments:
>
>1) That's Levoy, not LeVoy, and he's now Assistant Professor of Computer
>   Science at Stanford.
>
>2) For rendering clouds, volume rendering is not the correct approach.
>   For one thing, the spatial location of the points in a cloud are not
>   restricted to a grid as is volume data.
>

As discussed fairly extensively at the San Diego Volume Visualization
Workshop (December 1990), there is a lot of volume data that is NOT 
defined on regular grids.  Fluid dynamics uses warped grids; finite element
analysis and other fields use "grids" in which cells may have more or fewer
than six faces.  None the less, these applications may profit from
volume rendered display of their data.  It is just harder to do.  ( :-) )

>3) At SIGGRAPH `91, there will be a course called,
>  "Photo-realistic Volume Modeling and Rendering Techniques".
>   The lectures include James Kajiya of CalTech and Ken Perlin of NYU.
>    Topics include "volume tracing techniques for rendering
>   atmospheric effects and laminar flame model; volume rendering of soft
>   objects". Get a copy of the course notes at SIGGRAPH.
>
>4) Consult the publications of Kajiya, Blinn, Perlin and others for tips
>   on rendering fuzzy clouds.
>
>Paul O'Keefe
>SUNY at Buffalo

Sam Uselton		uselton@nas.nasa.gov 		
employed by CSC		working for NASA (Ames)		speaking for myself
			volume rendering vector fields on warped grids!