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From nucsrl!casbah.acns.nwu.edu!zaphod.mps.ohio-state.edu!wupost!uunet!psinntp!eye!erich Wed Nov 20 19:47:14 CST 1991
Article: 5590 of comp.graphics
Path: nucsrl!casbah.acns.nwu.edu!zaphod.mps.ohio-state.edu!wupost!uunet!psinntp!eye!erich
From: erich@eye.com (Eric Haines)
Newsgroups: comp.graphics
Subject: Ray Tracing News, Volume 4, Number 3
Message-ID: <1991Nov20.153217.19599@eye.com>
Date: Wed, 20 Nov 91 20:32:16 GMT
Sender: Eric Haines
Organization: 3D/EYE, Inc. Ithaca, NY
Lines: 869
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"Light Makes Right"
November 18, 1991
Volume 4, Number 3
Compiled by Eric Haines, 3D/Eye Inc, 2359 Triphammer Rd, Ithaca, NY 14850
erich@eye.com
All contents are US copyright (c) 1991 by the individual authors
Archive locations: anonymous FTP at weedeater.math.yale.edu [130.132.23.17],
/pub/RTNews, and others.
UUCP archive access: write Kory Hamzeh (quad.com!avatar!kory) for info.
Contents:
Introduction
New People, Address Changes, etc
ElectroGig Free Software Offer
Spectrum: A Proposed Image Synthesis Architecture, by Andrew Glassner
Spline Intersection, Texture Mapping, and Whatnot, by Rick Turner
Satellite Image Interpretation, by Andy Newton
Material Properties, by Ken Turkowski
New Library of 3D Objects Available via FTP, by Steve Worley
Object Oriented Ray Tracing Book
New and Updated Ray Tracing and Radiosity Bibliographies
DKBTrace 2.12 Port to Mac, by Thomas Okken
Graphics Gems II Source Code
Radiance Digest Archive, by Greg Ward
Model Generation Software, by Paul D. Bourke
Rayshade 4.0 Release, Patches 1 & 2, and DOS Port, by Craig Kolb and
Rod Bogart
RayShade Timings, by Craig Kolb
RayShade vs. DKBtrace Timings, by Iain Dick Sinclair
PVRay Beta Release, by David Buck
Vort 2.1 Release, by Eric H. Echidna
BRL-CAD 4.0 Release, by Michael J. Muuss and Glenn M. Gillis
-------------------------------------------------------------------------------
Introduction
Well, it's been awhile - RealWork (TM) has been getting in the way of
putting out an issue of the Ray Tracing News. So, rewind your brains back to
August...
SIGGRAPH was interesting, as usual. Las Vegas is an amusing place; now
that I've seen it once, I don't ever need to go back. To my surprise, there
was quite a turnout for the ray tracing roundtable get together at SIGGRAPH.
The roundtable is a nice excuse for people to get in a room and put faces to
names, and I finally got to meet some people who had been just authors with
email addresses before this.
Some papers of note at SIGGRAPH which directly affect ray tracing were
Kirk & Arvo's paper on unbiased sampling techniques and Mitchell's on optimal
sampling for ray tracing. The first warns that re-using initial samples
results in bias when adaptively supersampling; the last talks of image
sampling strategies. Other papers of interest include those on new procedural
texturing methods, which all look fairly easy to implement in their simpler
forms.
Chen et al presented "A Progressive Multi-Pass Method for Global
Illumination", which does about every trick in the book to attempt to achieve
maximum realism. Xiao He et al presented "A Comprehensive Physical Model for
Light Reflection", which is just that; it seems about the most realistic
shading model I've seen, with some very serious mathematics behind it. Another
paper from Cornell, "A Global Illumination Solution for General Reflectance
Distributions" by Sillion et al, gives an interesting method of storing
reflectance functions by using spherical harmonics.
The most theoretically significant radiosity paper was done by Hanrahan et
al, who presented a method of limiting the amount of computation by use of
hierarchy and error limits. This method opens up interesting new lines of
thought and research in radiosity.
I did not spend a lot of time on the floor, but did run across an
interesting demo at the Intergraph booth. They had a cute ray tracing program
that implemented parameterized ray tracing (Sequin & Smyrl, SIGGRAPH '89),
where you essentially store the shading equation parameters for each pixel.
Changing colors, applying textures, etc then becomes pleasantly fast, as all
you have to do is substitute the proper parameter values and reevaluate,
getting a new full ray traced image in seconds.
Other new ray tracing products I noticed were from Ray Dream and Strata.
Ray Dream has a ray tracer for the Mac, with the program LightForge for
modeling surfaces and SceneBuilder for scene description. They have also
added a distributed computing feature to poll Macs on a network for idle CPU
time and uses it for rendering. Strata offers StrataVision 3d, again for the
Mac. They claim ray tracing and radiosity rendering and gave us a demo disk -
the radiosity images are no great shakes, but it's interesting to see the word
"radiosity" making its way into the microcomputer market.
AT&T Pixel Machines has been adding radiosity capabilities to their
rendering library set. Silicon Graphics is still demoing radiosity, though no
product seems in the offing. They did have a good tutorial film showing the
ideas behind the progressive radiosity algorithm, and Baum et al had a
worthwhile paper in the Proceedings on making radiosity usable. This paper is
indispensable for anyone designing a robust radiosity system for general use
(i.e. you plan on rendering more that a few axis aligned boxes in a room).
HP demoed their radiosity rendering product (ARTCore) with a room designer
demonstration, and had a movie in the film show (positive adjectives avoided,
since I worked on both projects).
One of the more clever tricks I learnt from the room designer was how to
get reasonable wallpaper, floor covering, and other such textures scanned in
using a flatbed scanner. In the past I went to building supply places and
borrowed or bought samples ("Yes, I want to see how this will look in my
kitchen", not mentioning that the kitchen existed only in the computer).
However, with a flatbed scanner you can get stuck: the samples can be bigger
than the scanning surface. Even if small enough, repetition of the texture
can lead to unrealistic effects (for example, a brick pattern is obviously
tiled if the brick colors keep repeating in a too regular fashion). I've also
tried photographing large areas of a surface (e.g. a brick wall), but then
variations in the scene's lighting often appear and make for patterning or odd
shading artifacts.
Tamar Cohen, who developed the room designer, realized that there was an
excellent solution to these problems: dollhouse supplies! Dollhouse
wallpaper and floor coverings easily fit on a flatbed scanner, and all the
repetition and lighting problems go away.
For those of you who are deeply into texturing, you should consider
looking into the Khoros image processing system (ftp from pprg.eece.unm.edu
[129.24.24.10]: /pub/khoros - check release first). It's a huge (~100 Meg)
system, but from my minimal exposure seems extremely powerful and easy to use.
It has a visual programming language, so you can interactively attach various
function boxes together to perform operations. This makes the system easy to
quickly start using for simple manipulations, though I think I'm going to have
to break down and read the documentation at this point. The system is X based
and has been ported to most major workstations on up, and the group at the
University of New Mexico are enthusiastic and willing to help. Recommended.
I've also finally scratched the surface of Greg Ward et al's Radiance
package. I was impressed first off by the portability: one