Graphics Plus/Graphics Plus.iso/info/rtnews/rtnv4n3

Text File | 1994-10-16 | 42.6 KB | 870 lines

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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
    [e-mail]
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 of his displayers
was the first serious X program I've ever compiled and linked without having
to diddle around with something to make it go.  In fact, I didn't even know it
was an X program until I ran it and a window popped up on the screen!  If you
want physically based rendering, this is the only package I know that even
attempts it.  It also seems to be a fine renderer, and I enjoy the progressive
ray tracing feature (the image refines while you watch it).

    As far as speed goes, Rich Marisa at the Cornell Theory Center kindly gave
me an explanation and demonstration of their Ray Casting Engine.  Duke and
Cornell have been developing this piece of hardware for some time, and it
embodies an interesting approach:  represent the CSG model as a network of
processors, then, given a direction of view, convert the model into sets of
spans.  These spans can then be used for analysis, rendering, etc.  For more
information, see the Feb. 1991 issue of Mechanical Engineering, or Kedem and
Ellis' article in _Parallel Processing of Computer Vision and Display_ (ed.
by Dew, Heywood & Earnshaw).

-------------------------------------------------------------------------------

New People, Address Changes, etc


# Andy Newton - physical radiance modelling, natural scenes, rays with solid
#    angle
# Remote Sensing Research, University College London
# Photogrammetry,
# UCL, Gower Street
# London, ENGLAND
# [phone] x2742
alias andy_newton    [e-mail]
alias andy_newton    [e-mail]

Although the graphics is more fun than the Remote Sensing this is what I'm
supposed to be doing ...

Applying ray tracing to the understanding of remote sensed images of the
natural world, mainly satellite imagery. Much more interested in physical
accuracy than efficiency. Also how to correctly model, and sample, very large
and non-uniform light sources (the sky!) in ray tracing. How to relate the
point sampling paradigm of the infinitesimal ray to light energy transport.
Physical reflectance models like BRDF. Doing distance attenuation and variable
light source sampling properly (probably) using solid angle.

I'd be really interested in any references anyone has to ray tracing for
physical process simulations or radiance calculations using solid angle as
a ray property.

On offer: a realistic sky radiance model based on atmospheric scattering.

--------

# Denise Blakeley
# 1455 Runaway Bay Dr. #2B
# Columbus, OH 43204
# [phone]
[e-mail]

Ray-tracing interests: general

What I'm doing these days: I'm trying to finish my MS in Computer Science
  (concentrating in graphics) here at Ohio State December '91.  I'd like to
  finish the program with at least one fairly complete project to show for
  it, so I'm trying to expand my basic ray-tracer into a more complete
  rendering system.  Nothing ground-breaking; I'm just trying to learn as
  much as I can at this point, and have fun doing it!

--------

# Rick Turner - weird primitives, non-Euclidean raytracing, textures
# IBM UK Science Centre
# Athelstan House, St. Clement Street, Winchester SO23 9DR, England.
[e-mail]

I'm a scientist at UKSC, working in the area of remote sensing and the
application of image and visualisation techniques to earth science problems.
Raytracing is a spare time activity.  I've written one raytracer, as well as a
substantial part of a second.  These use all the common CSG primitives, and
for the large tracer (called RT), I've added support for bicubic spline
patches (bezier, b-spline, ..., continuous beta-splines) and implicit
functions as well.  Currently I'm playing around with texture and image
mapping and volume objects.

--------

Matthew Williams
501 Chapel Drive #1417
Tallahassee, Fl  32304
[phone]
[e-mail]

Interests: Anything and everything

At the moment I am a student at Florida State University majoring in Russian
Language with minors in Math, Physics, and Computer Science.  All the time
that I am not in class (including some times when I should be in class) I am
on my PC playing around with DKBTrace (or should I say PVRay).  One of my
larger projects that I want to attempt is translating the C source for DKB to
assembly and hopefully gain some speed.  I would also like to add a fractal
section to it so I can have vines and stuff growing on different objects.

-------------------------------------------------------------------------------

ElectroGig Free Software Offer

[I don't know much about GIG, except that they have a CSG ray tracer.  Sounds
like quite a deal, though! - EAH]

From Communications of the ACM, Nov. 1991:

In an effort to enhance computer graphics education on a national level, GIG
USA is offering a limited number of complete 3D graphics packages free of
charge to accredited universities, colleges and schools throughout the U.S.
The ElectroGIG system, which lists for $30,000, includes retracing [sic -
should be ray-tracing] and animation applications and runs on Silicon Graphics
and DEC 5000 workstations.  Written requests must be mailed (phone calls or
faxes will not be accepted) on official school letterhead by staff or faculty
members only to GIG USA, Inc., 7380 Sand Lake Rd., Suite 390, Orlando, FL
32819, attention:  GIG Educational Software Program.

-------------------------------------------------------------------------------

Spectrum: A Proposed Image Synthesis Architecture, by Andrew Glassner
    ([e-mail])

Andrew Glassner is currently working on a proposal called "Spectrum", which is
a new ray tracer architecture.  The document outlining this design was made
available in the "Frontiers in Rendering" course notes.  The idea is to make a
flexible public domain ray tracer available among researchers and educators.

-------------------------------------------------------------------------------

Spline Intersection, Texture Mapping, and Whatnot, by
    Rick Turner ([e-mail]) and Eric Haines

The code that I developed is based essentially on algorithms developed by
Kajiya and extended by Marini et al (the paper is in one of the Eurographics
procs; I can dig out a reference for you if you're interested).  Basically, we
model the ray as a pair of orthogonal planes.  Each of these is intersected
with the spline surface, giving a pair of space curves.  You intersect the
space curves giving the ray/surface intersection.

Intersecting curves is a manageable problem, so it works quite well.  The same
basic method is employed for all types of bicubic spline surface.  It actually
turns out that splines having a constant basis matrix (eg b-spline, power
splines, hermites, Catmull-Rom splines etc) are cheaper to compute if you
first do a basis transformation to bezier splines.  Beta splines and so on
that have a variable basis matrix require special treatment, which is quite
complex.

I run the code on an i860 based accelerator card to get it to work in
reasonable time; a 1024*1024 image with a few hundred primitives takes 5-10
minutes to compute.  Spline surfaces can increase this considerably.

The raytracer in question was originally developed by IBM Poughkeepsie as part
of a system called GDP (Geometric Design Processor).  This was essentially a
CSG system and was used to design parts of IBM mainframes.  It ran on a
mainframe and was written in PL/I and Assembler.  The mainframe code was
hacked out as a standalone module some years ago, and was then re-written in
'C' in peoples spare time.  Most of the basics were done in Burlington, Va.,
though extensions were done all over the place.

I'm currently working with mapping images and textures onto objects.  Yes, I
know this is a largely solved problem nowadays, but there are some interesting
'gotchas'.  I'm particularly interested in singular mappings, where you don't
have a one-to-one correspondence.  This overlaps in some ways with my 'real'
work, which often involves rendering some earth science dataset.  I'm
currently fooling around with Magellan data from JPL, rendering combinations
of terrain and image data in various ways.

--------

My reply:

I know the two-plane intersection method you refer to, in fact I coded it up
once long ago (though I don't know the Marini paper - maybe he solves the
problem of sometimes converging on the farther intersections instead of the
closest?  Seems like I remember that guaranteeing the right root is found was
a headache, though I recall Kajiya's solution was something like "use
Laguerre's method and find them all" or somesuch - I'm probably mixing this
up, as I haven't looked at these numerical methods in years...)

As far as texture mapping, that's something I'm still playing with here, too.
Solved?  Well, how does adaptive sampling work along with textures and mipmaps
and so on (mipmaps sample area, but what do you do if more sample rays are
shot in a pixel?) - there was a paper on this topic in Eurographics '91, so
it's of interest.  Also, specifying parameterizations for sets of primitives
is easy enough in theory (e.g. define some projection (spherical, conical,
plane) in space and use this to determine xyz -> uv), but this kind of thing
can look really bad in some cases.  I've been playing with other
parameterization functions, with some interesting results (my VW bug covered
with straw weave is certain to become a style trend soon, I'm sure).  Have you
run across any interesting parameterization papers/techniques lately?

--------

Reply from Rick:

In my code, the patches are subdivided, though not by very much.  Each
'mini-patch' has its own bounding box, and both are built into a tree
structure.  The more curvature the patch has, the greater the subdivision that
will be used; this reduces the chances of having a local maximum or minimum in
the middle of the patch go outside the bounding box.  It also allows you to
fit the bounding boxes much more tightly to the surface, so cuts down the
number of false intersections where the ray intersects the bounding box but
not the surface.  One interesting side effect of the subdivision is that by
making the bounding box smaller than the surface, you get disconnected pieces
of surface floating in space.  A nice example of this is on the cover of the
Bartels/Beatty/Barsky book on splines.  I've done the teapot in a similar way,
and it looks rather neat.  I went further and mapped the baboon onto each
disconnected patch, and it's quite eye catching.

Basically, the convergence method is a hybrid of multi-dimensional conjugate
gradient and quasi-Newton techniques.  This offers speed plus reasonable
stability (although you can always find a pathological case to defeat the
algorithms).  One thing about it is that the iterations happen in (u,v) space
rather than in (x,y,z) space; this ensures that the iterations will always
converge to a valid solution; if either u or v go outside the range valid for
the particular mini-patch that you're testing against you can immediately
reject the solution, as there will be no intersection with that patch.
Typically false intersections such as this are rejected on the first (or
sometimes the second) iteration, which improves the performance a bit.

Ray tracing splines is tedious though, so I've given my code an option to
render the bounding boxes for the mini-patches.  This gives a pretty good
first look at what you're going to get out, and takes a couple of orders of
magnitude less time.

Texture mapping people may want to look through the cartographic literature.
Map makers have similar problems in projective geometry when it comes to
changing map (or image) coordinate systems - eg, from Lat/Long to UTM for
example.  Much effort has been devoted to solving the mapping (in the
mathematical sense) problem; less on resampling.  Almost always the resampling
used are standard bi-linear or bi-cubics with the attendant problems.  On the
whole though, digital cartography can be a useful source on information that
is often overlooked by graphics people.  A good reference to start with is
USGS Professional Paper 1395, 'Map Projections, a Working Manual' by John
Snyder.  In the US you can get a copy from any Government bookstore - when I
got mine I think that it cost me about 25 dollars.

-------------------------------------------------------------------------------

Satellite Image Interpretation, by Andy Newton ([e-mail])

I work in a satellite image interpretation research group. Our interest in
ray tracing is for simulating all parts of the process of the formation of
satellite images - optics, camera motion, atmosphere, surface scattering and
global (as in hemispherical!) light source illumination. We do work at two
scales - where the basic scene is a DEM (height grid) and for very complicated
3-d scenes for plant canopy reflectance simulation.

So ray tracing is a really powerful tool to allow us to simulate as many parts
of these complex processes as we can model but what we need to do is not quite
computer graphics. What I mean by this is that what we need out of our models
are accurate, truthful, energies (in real units) not measures of visual
brightness. We need physical results. One example of this is wavelength sampling
by importance sampling a spectral response curve as opposed to treating light as
an RGB 'colour'. (Though I can't recall any references to doing exactly this it
is proposed in Cook's original stochastic sampling papers and my implementation
is very similar to his for reflected ray direction).

Our main problems are (i) illumination from such a big light source (the sky
hemisphere) with 'diffuse' reflectors (ii) ensuring that we model energies
correctly and (iii) using physical directional reflectances. I may be going out
on a bit of a limb here so please excuse me if I do - I'm not as familiar as I
ought to be with general CG practice - but I'll try to explain what I mean.

I've spent the better part of 3 years supporting and trying to add to a tracer
I inherited when I came to work here. Now that has turned out not to be
particularly smart as its been a lot harder to modify and bug fix than if it was
my own work. Anyway the point is that through out most of that time we had no
good model for the directional and spectral variation of that thing outside the
window - the sky. As our main interest is _supposed_ to be the satellite work,
not the graphics, I felt we couldn't come to grand conclusions from our results
if the illumination function was simply not representative of the real world.
Now I've managed to solve this problem by implementing a model of atmospheric
scattering processes due to Zibordi and Voss so its time to make the physics
correct and BTW write a fresh tracer. I have seen some work on CG models of the
sky which are functional and not physical. This model is quite fast enough to
create a sky radiance LUT at any resolution required on a per scene basis so if
you know of anyone out there who needs a model of the sky's irradiance maybe I
could help.

The thing about any such illumination model is, of course, that the energy
results are per steradian of solid angle of illuminating source.  With the
point sampling infinitesimally thin ray what solid angle does a ray reaching
the sky have?  If it's a primary ray then OK it can have some solid angle
associated with the pixel but how should ray solid angles be transformed by
reflection etc?  The only work I've seen that is remotely like this is
Amantide's cones.  However that doesn't use the geometric concept of a solid
angle.  One plus point of considering solid angle is of course that the
effects of distance attenuation by divergence are implicitly included.  So I'm
very interested in how much solid angle is used as yet another ray parameter
in more general CG work.  Is this really common, or unheard of?

There's a reflectance concept in remote sensing called Bi-Directional
Reflectance Distribution Function (BRDF), which may also be use in CG or have
a parallel, that defines directional reflectance as a 5-d array of pairwise
directional spectral reflectance coefficients.  For each wavelength
(quantized, of course), for each incident direction (over the 2 Pi
hemisphere), for each emergent direction, define a reflectance coefficient.
Such things can be used as reflectance LUTs or integrated, subdivided and
importance sampled.  Are similar things done for interesting material
reflectances in the main stream?

-------------------------------------------------------------------------------

Material Properties, by Ken Turkowski ([e-mail])

[I edited Ken's notes into a coherent whole. - EAH]

>Does anyone know where I can pick up a list of material properties for
>different metals and other objects?
>
>I need to know refractive index, diffuse component, specular component and
>specular exponent.

Purdue has a catalog of transmissive, reflective, absorptive and emissive
spectral data for conductors, dielectrics, pigments, emulsions, and light
sources.  From this you can calculate the refractive index and diffuse
spectrum.  It's called _Thermophysical Properties of Matter_ by the Purdue
University Thermophysical properties research center.  There are multiple
volumes.  We have found volumes 6, 7, and 8 most useful.  These contain data
for dielectrics, conductors, and surface coatings.

Unfortunately, this book is out of print.  We got our copy by photocopying one
that Purdue had.

Specular data is a function of the finish (i.e. rough, smooth), and can be
calculated by the method of He (SIGGRAPH '91) given surface statistics.

Roy Hall's book, _Illumination and Color in Computer Generated Imagery_,
points to some other sources of reflective data.  The reflective spectrum *is*
the diffuse "color".  Specular properties are a function on the finish, not
the material.

-------------------------------------------------------------------------------

New Library of 3D Objects Available via FTP, by Steve Worley
    ([e-mail])

On the ftp site cs.uoregon.edu (128.223.4.13), I have assembled a set of over
150 3D objects in a binary format called TDDD in the directory
/incoming/TDDDobjs.  These objects range from human figures to airplanes, from
semi-trucks to lampposts.  These objects are all freely distributable, and most
have READMEs that describe them.  There are over six megabytes of these binary
objects.

In order to convert these objects to a human-readable format, a file with the
specification of TDDD is included in the directory with the objects.  There is
also a shareware utility called TDDDconv that will convert the binary objects
into either OFF, NFF, Rayshade, or vort objects.  This utility is also found
on cs.uoregon.edu, in the file /incoming/TDDDconv.tar.Z.

[There are some interesting things here.  You might have to diddle a bit, and
I noticed that some databases don't translate, but good stuff for the price!
One very cute thing in the package is "tddd2ps", which "converts" a TDDD file
to a printable set of four orthogonal views - nice touch!  - EAH]

-------------------------------------------------------------------------------

Object Oriented Ray Tracing Book

> I am looking for a book named "Object-oriented ray_tracing" by Melcher,
> and published by Wiley 91.

This is, in fact, an article by Karl Melcher and G. Scott Owen, more fully
entitled "Object Oriented Ray Tracing: A Comparison of C++ Versus C
Implementations" which will appear in a Wiley book early in 1992 (and which
was in the Wiley booth at SIGGRAPH '91).  The title of the book will be
"Computer Graphics Using Object-Oriented Programming" and the editors are
Cunningham, Craighill, Fong, and Brown.

-------------------------------------------------------------------------------

New and Updated Ray Tracing and Radiosity Bibliographies

At weedeater (see the header of this issue) via anonymous FTP are a number of
new or updated ray tracing and radiosity bibliographies.  I've updated the
ray tracing bibliography (pub/Papers/RayBib.09.91.Z) and radiosity bib
(RadBib.09.91) from last year's version.  Rick Speer has provided a postscript
(only) version of his extensively cross-referenced ray tracing bibliography
(speer.raytrace.bib.ps).  Tom Wilson's fine ray tracing abstract collection is
also available, with June 1 being the latest version (rtabs.6.91.shar.Z).
Also, the file "NetPapers" lists a number of worthwhile articles and theses
available on the net and where to get them.

-------------------------------------------------------------------------------

DKBTrace 2.12 Port to Mac, by Thomas Okken ([e-mail])

The public-domain raytracer DKBTrace, which runs on FPU-equipped Macs, has
been made available for anonymous ftp from "alfred.ccs.carleton.ca", files
/pub/dkbtrace/dkb2.12/other_ports/MacPort1.0.2.*.

-------------------------------------------------------------------------------

Graphics Gems II Source Code

FTP from:

weedeater.math.yale.edu [130.132.23.17]
gondwana.ecr.mu.oz.au [128.250.1.63]

file: pub/GraphicsGems/GemsII/GGemsII.tar.Z

-------------------------------------------------------------------------------

Radiance Digest Archive, by Greg Ward ([e-mail])

I have just made back issues of the Radiance Digest available from anonymous
ftp at hobbes.lbl.gov (128.3.12.38) in the pub/digest directory.  Those of you
who have limited network access can still ask me to send back issues to you
directly.

-------------------------------------------------------------------------------

Model Generation Software, by Paul D. Bourke ([e-mail])

[Paul has a facet based modeller for the Mac called VISION-3D, which can be
used to generate models directly in the RayShade and Radiance file formats.
He wrote telling me of other programs that might be of interest - EAH]

I have some other "niche" model generators that also export to Radiance and
RayShade.

A brief description of some of them follows:

FracHill - generates the old fractal landscapes using the spatial subdivision
           technique (ie: not the fourier method) It has all the usual
           settings for roughness, sea level, seed, land/sea colour, etc

3D LSystems - allows the user to generate 3D LSystems (0L). Uses all the
              standard symbols from the literature, an extension of my
              2D LSystem which I wrote years ago.

Triangulate - takes a set of randomly distributed samples on a surface and
              generates either a triangulated (Delaunay) of gridded mesh
              representing the surface. We use it for our landscape
              Architecture course. Note: surfaces (functions) only, not
              solids!

Anyway, these and other applications can be obtained from my FTP directory
   [e-mail] (130.216.1.5)
located in the
   architec
directory. Because we pay for FTP to the US people should be asked to FTP
the README file in the above directory, it will inform them of alternative
sites in the US.

-------------------------------------------------------------------------------

Rayshade 4.0 Release, Patches 1 & 2, and DOS Port, by Craig Kolb and Rod Bogart
    ([e-mail])

Rayshade 4.0 is now available.  This version is extremely different from 3.0,
and is very different from 4.0beta.

Rayshade 4.0 features include:
    + Eleven primitives (blob, box, cone, cylinder, height field,
        plane, polygon, sphere, torus, flat- and Phong-shaded triangle)
    + Aggregate objects
    + Constructive solid geometry
    + Point, directional, extended, spot, and quadrilateral light sources
    + Solid procedural texturing, bump mapping, and
        2D "image" texture mapping
    + Antialiasing through variable-rate "jittered" sampling
    + Arbitrary linear transformations on objects and texture/bump maps.
    + Use of uniform spatial subdivision or hierarchy of bounding
        volumes to speed rendering
    + Options to facilitate rendering of stereo pairs
    + Rudimentary animation support and motion blur
    + Numerous bug fixes and syntax changes

Apologies to all the folks who felt that their Rayshade 4.0beta questions were
not handled in a timely fashion.  Both Rod and Craig have had to deal with
Real Life and did not have as much time for Rayshade as we had hoped.  We
still feel that Rayshade is the best Un*x raytracing package for the price.

Rayshade 4.0 is available via anonymous ftp from weedeater.math.yale.edu
(130.132.23.17) in pub/rayshade.4.0.  The shar files will be posted to
alt.sources and submitted to comp.sources.misc.

--------

Patches 1 and 2 to rayshade 4.0 are now available through
anonymous ftp from weedeater.math.yale.edu (130.132.23.17)
as pub/rayshade.4.0/patches/patch{1,2}.  The patches have
also been posted to comp.sources.misc.

--------

Tom Hite managed to port rayshade to DOS, and was kind enough to send me
a set of diffs, a couple of configuration files, and a short note describing
what one needs to do in order to coax rayshade into running on PCs.

I haven't had the courage yet to find myself a PC and to verify that Tom's
instructions are idiot-proof.  In addition, Tom's diffs were for rayshade 4.0
patchlevel 0, and the new patches will undoubtedly cause some minor problems
when it comes to applying Tom's diffs.

The files are available from weedeater.math.yale.edu (130.132.23.17) as
pub/rayshade.4.0/raydiffs.dos.

-------------------------------------------------------------------------------

RayShade Timings, by Craig Kolb

Below for your amusement(?)  are timings for the latest version of rayshade
running on an HP-730.

I suspect that rayshade is a good bit less efficient than it used to be, but
I have yet to actually put this suspicion to the test.


Rayshade v4.0, patchlevel 1, on an HP-730 running HPUX-8.05, ?? MB memory.
Wed Oct  9 13:50:29 EDT 1991

         Setup       Total     |  Polygon   Sphere    Cyl/Cone    Bounding
             (seconds)         |   Tests     Tests      Tests    Box Tests
--------------------------------------------------------------------------
balls     3.18       116.24    |    356K     1564K        0        2763K
gears    15.79       705.25    |   8345K       0          0       11260K
mount     6.13       165.03    |   1035K     2096K        0        2991K
rings     5.44       235.37    |    103K      206K      4883K      5536K
teapot   13.49       126.43    |   1677K       0          0        2761K
tetra     2.96        31.93    |    578K       0          0         694K
tree      4.94       103.28    |    716K       16K       366K      1467K

All timings are sum of user and system time.  Setup includes time to read
the database and initialize all appropriate data structures.  Total time
is setup time plus rendering time.  Test figures are rounded upwards.

Uniform spatial subdivision, employing 22^3 voxels, is used to accelerate
rendering.  In the balls, gears, and tree databases, the ground plane
is moved outside of the 22^3 grid in an attempt to generate a more uniform
object distribution within the grid.

-------------------------------------------------------------------------------

RayShade vs. DKBtrace Timings, by Iain Dick Sinclair ([e-mail])

>    In your posting on RayShade vs. DKBtrace you mention doing timings
>on them using the SPD.  Any chance you have the timings sitting around?

A friend here did the comparison, but it was by no means thorough -- it only
used one benchmark (the balls?).  In any event, the results of his quick
experiment seem to have been discarded (apparently it was a slight pain to
translate NFF -> DKB's verbose input format).  I seem to remember him saying
that Rayshade completed the scene about 20% quicker.  Unfortunately, SPD
wasn't used exhaustively, though it may be in the near future.

-------------------------------------------------------------------------------

PVRay Beta Release, by David Buck ([e-mail])

The freely distributable raytracer PVRay (Persistence of Vision) is
available for BETA testing from alfred.ccs.carleton.ca (134.117.1.1)
in the directory pub/dkbtrace/pvraybeta.  This program has been
developed by the "Persistence of Vision" group on CompuServe and is
built on top of DKBTrace version 2.12 with my permission and blessing.

Please note that this is a BETA release, so it may exhibit some bugs or
portability problems to different platforms.  Please refer any
problems to Drew Wells at [e-mail].  Also, this
version does not contain some of the ports which were previously
available for DKBTrace.  This situation is being rectified.  However,
you should find that the product-specific modules developed for
DKBTrace should be easily adaptable to PVRay.

Program Synopsis:
-----------------

PVRay is a Freely Distributable raytracer built on top of DKBTrace.  New
additions include:

   - Bezier surfaces
   - Height Fields (GIF only at this time)
   - Bump maps
   - Improved Quartic surface support
   - Input language can now optionally accept lowercase keywords
   - New textures: Onion, Leopard
   - C-style comments accepted (  /* */ and //)
   - Algebraic surfaces
   - Sphere, Cylinder, and Torus image mappings

Please direct inquiries to Drew Wells at [e-mail].

-------------------------------------------------------------------------------

Vort 2.1 Release, by Eric H. Echidna

    gondwana.ecr.mu.oz.au [128.250.1.63] pub/vort.tar.Z
    munnari.oz.au [128.250.1.21] pub/graphics/vort.tar.Z
    uunet.uu.net [192.48.96.2] graphics/vogle/vort.tar.Z
     (uucp access as well ~ftp/graphics/vogle/vort.tar.Z)

Australian ACSnet sites may use fetchfile:
    fetchfile -dgondwana.ecr.mu.oz pub/vort.tar.Z

The major changes are to the ray-tracer which now allows orthographic
projections, lights to be in composite objects, provides a transform operator,
a few other odds and sods plus the usual set of bug fixes.  There are also a
couple of utilities for starting art up via inetd to help simplify the
generation of animations across networks.

It runs on IBM PC's, VMS, and a variety of UNIX boxes.

Contributed scene files for the ray-tracer can be found in contrib/artscenes
on gondwana.  Apart from the scene files the tar files in this directory also
includes some useful tile patterns and geometry files.

Anyone with anything they'd like to add is welcome to put it in gondwana's
incoming directory and send us mail.

Includes [among much else]:

art    - a ray tracer for doing algebraic surfaces and CSG models.

-------------------------------------------------------------------------------

BRL-CAD 4.0 Release, by Michael J. Muuss and Glenn M. Gillis

The U. S. Army Ballistic Research Laboratory (BRL) is proud to announce
the availability of Release 4.0 of the BRL-CAD Package.

The BRL-CAD Package is a powerful Constructive Solid Geometry (CSG) based
solid modeling system.  BRL-CAD includes an interactive geometry editor, a ray
tracing library, two ray-tracing based lighting models, a generic framebuffer
library, a network-distributed image-processing and signal-processing
capability, and a large collection of related tools and utilities.  Release
4.0 is the latest version of software which has been undergoing continuous
development since 1979.

The most significant new feature for Release 4.0 is the addition of n-Manifold
Geometry (NMG) support based on the work of Kevin Weiler.  The NMG software
converts CSG solid models into approximate polygonalized boundary
representations, suitable for processing by subsequent applications and
high-speed hardware display.

BRL-CAD is used at over 800 sites located throughout the world.  It is
provided in source code form only, and totals more than 280,000 lines of "C"
code.

BRL-CAD supports a great variety of geometric representations, including an
extensive set of traditional CSG primitive solids such as blocks, cones and
tori, solids made from closed collections of Uniform B-Spline Surfaces as
well as Non-Uniform Rational B-Spline (NURBS) Surfaces, purely faceted
geometry, and n-Manifold Geometry (NMG).  All geometric objects may be
combined using boolean set-theoretic operations such as union, intersection,
and subtraction.

Material properties and other attribute properties can be associated with
geometry objects.  This combining of material properties with geometry is a
critical part of the link to applications codes.  BRL-CAD supports a rich
object-oriented set of extensible interfaces by means of which geometry and
attribute data are passed to applications.

A few of the applications linked to BRL-CAD include:

*) Optical Image Generation (including specular/diffuse reflection,
    refraction, multiple light sources, and articulated animation)
*) An array of military vehicle design and evaluation V/L Codes
*) Bistatic laser analysis
*) Predictive Synthetic Aperture Radar Codes (including codes due to ERIM)
*) High-Energy Laser Damage
*) High-Power Microwave Damage
*) Weights and Moments-of-Inertia
*) Neutron Transport Code
*) PATRAN [TM] and hence to ADINA, EPIC-2, NASTRAN, etc.
    for structural/stress analysis
*) X-Ray image calculation

BRL-CAD requires the UNIX operating system and is supported on more than a
dozen product lines from workstations to supercomputers, including:  Alliant
FX/8 and FX/80, Alliant FX/2800, Apple Macintosh II, Convex C1, Cray-1, Cray
X-MP, Cray Y-MP, Cray-2, Digital Equipment VAX, Gould/Encore PN 6000/9000, IBM
RS/6000, Pyramid 9820, Silicon Graphics 3030, Silicon Graphics 4D ``Iris'',
Sun Microsystems Sun-3, and the Sun Microsystems Sun-4 ``SparcStation''.
Porting to other UNIX systems is very easy, and generally only takes a day or
two.

You may obtain a copy of the BRL-CAD Package distribution materials in one of
two ways:

1.  FREE distribution with no support privileges:  Those users with online
access to the DARPA InterNet may obtain the BRL-CAD Package via FTP file
transfer, at no cost, after completing and returning a signed copy of the
printed distribution agreement.  A blank agreement form is available only via
anonymous FTP from host ftp.brl.mil (address 128.63.16.158) from file
"brl-cad/agreement".  There are encrypted FTP-able files in several countries
around the world.  Directions on how to obtain and decrypt the files will be
sent to you upon receipt of your signed agreement.  One printed set of BRL-CAD
documentation will be mailed to you at no cost.  Note that installation
assistance or telephone support are available only with full service
distributions.

2.  FULL SERVICE distribution:  The Survivability/Vulnerability Information
Analysis Center (SURVIAC) administers the supported BRL-CAD distributions and
information exchange programs for BRL.  Full service distributions cost
US$500, and include a copy of the full distribution materials on your choice
of magnetic tape media.  You may elect to obtain your copy via network FTP.
One printed set of BRL-CAD documentation will be mailed to you.  BRL-CAD
maintenance releases and errata sheets will be provided at no additional
charge, and you will have access to full technical assistance by phone, FAX,
letter, or E-mail.  Agencies of the U.S.  Federal Government may acquire the
full service distribution with a simple MIPR or OGA funds transfer.

For further details, call Mr. Glenn Gillis at USA (410)-273-7794, send E-mail
to <[e-mail]>, FAX your letter to USA (410)-272-7413, or write to:

    BRL-CAD Distribution
    SURVIAC Aberdeen Satellite Office
    1003 Old Philadelphia Road
    Suite 103
    Aberdeen MD  21001  USA

Note that USA area code 410 will not go into effect until 1-Nov-91.  Prior to
that date, please use area code 301.

Those sites selecting the free distribution may upgrade to full service status
at any time.  All users have access to the BRL-CAD Symposia, workshops, user's
group, and E-mail mailing list.

Sincerely,

Michael J. Muuss            Glenn M. Gillis
Advanced Computer Systems        SURVIAC
Ballistic Research Lab            Aberdeen Satellite Office

-------------------------------------------------------------------------------
END OF RTNEWS