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Newsgroups: comp.graphics,comp.answers,news.answers
From: grieggs@netcom.com (John T. Grieggs)
Subject: (10May95) comp.graphics Frequently Asked Questions (FAQ)
Message-ID: <grieggsD8DJz4.9CD@netcom.com>
Keywords: FAQ, graphics
Sender: grieggs@netcom19.netcom.com
Reply-To: grieggs@netcom.com (John T. Grieggs)
Organization: Grizzly Bear Labs, Pasadena, Ca
Date: Wed, 10 May 1995 18:13:51 GMT
Approved: news-answers-request@MIT.edu
Archive-name: graphics/faq
COMP.GRAPHICS FAQ
Last update: 10May95
This document answers a number of the most frequently asked questions
about graphics on the Internet. To avoid wasting bandwidth and as a
matter of politeness please look for the answer to your question in
this document BEFORE posting to comp.graphics.
If your copy of the FAQ is more than a couple of weeks old, you may
want to seek out the most recent version. The latest non-HTML version
of this FAQ is always available on rtfm.mit.edu as
/pub/usenet/news.answers/graphics/faq.
In case you're reading the ASCII version of the FAQ, the HTML version
is at http://www.primenet.com/~grieggs/cg_faq.html.
Send your updates to me at grieggs@netcom.com. I reserve the right to
reject or modify submissions based on my interpretation of the role of
the FAQ.
_________________________________________________________________
Contents
* Editorial
* Changes since last revision
* Other Graphics-related FAQs and FAQ-like documents
* General References
+ Books
+ Eratta
+ Other
* Specific References
+ Ray-Tracing and Global Illumination
+ Graphics File Formats
+ Spatial Data Structures
+ PEX and PHIGS
+ OpenGL
+ Morphing
+ Radiosity
* How do I ...
+ draw 3D objects on a 2D screen?
+ quantize 24-bit images down to 8 bits?
+ convert color to grayscale?
+ convert grayscale to black & white?
+ rotate a raster image by an arbitrary angle?
+ draw a circle as a Bezier (or B-spline) curve?
+ tell whether a point is within a planar polygon?
+ tessellate a sphere?
+ ray-trace height fields?
+ find the area of a 3D polygon?
+ convert between vector formats?
+ get files if I can't ftp?
* Where can I get ...
+ format documents for TIFF, IFF, GIF, etc.?
+ free image manipulation software?
+ free plotting software?
+ standards documents?
+ 3D objects?
+ MRI and CT scan volume data?
+ MPSC and AOEGA info?
* Graphics-related Mailing Lists
+ Imagine mailing list
+ DCTV mailing list
+ Rayshade Users mailing list
+ Lightwave mailing list
+ Video Toaster mailing list
+ Mailing List For Massive Parallel Rendering
+ Netpbm mailing list
+ POV-Ray mailing list
+ RayDream mailing list
+ Computational Geometry mailing list
+ Photoshop mailing list
+ 3DStudio mailing list
+ KPT mailing list
+ KODAK Photo CD mailing list
+ Caligari TrueSpace mailing list
+ Global Illumination mailing list
* SIGGRAPH
+ SIGGRAPH information online
+ How to join ACM/SIGGRAPH
+ SIGGRAPH Online Bibliography Project
_________________________________________________________________
Editorial
No news is good news, unless of course you were expecting news, in
which case your news server may be down, which is bad news after all.
_john
_________________________________________________________________
Changes since last revision
KODAK Photo CD mailing list (erich@eye.com).
Caligari Truespace mailing list (erich@eye.com).
Dore' blurb update (bdealwis@Newbridge.COM).
New maintainer and URL for c.g.animation FAQ
(dejesus@vislab.navy.mil).
Better link for "Liberia..." (egilk@oslonett.no).
Global Illumination mailing list (Francois.Sillion@imag.fr).
Don't forget to send your contributions to grieggs@netcom.com! If you
just post, I may not see it for one reason or another...
_________________________________________________________________
Other Graphics-related FAQs and FAQ-like documents
The comp.graphics FAQ attempts to cover a wide range of material. If
you don't find what you need here, try one of these more focused
documents.
comp.graphics.algorithms FAQ
Maintained by Jon Stone (jdstone@destin.dazixco.ingr.com), the
comp.graphics.algorithms FAQ contains questions and answers
about computer graphics algorithms. There is some overlap
between this document and the one you are reading, for
historical reasons. It is available on rtfm.mit.edu as
/pub/usenet/news.answers/graphics/algorithms-faq.
comp.graphics.animation FAQ
Maintained by Francisco X DeJesus (dejesus@vislab.navy.mil),
the comp.graphics.animation FAQ contains questions and answers
about computer graphics animation. He maintains a HTML version
at http://www.ridgecrest.ca.us/fx/cga-faq.html. The non-HTML
version is still available on rtfm.mit.edu as
/pub/usenet/news.answers/graphics/animation-faq.
Graphics File Formats FAQ
Maintained by James Murray (jdm@netcom.com), the Graphics File
Formats FAQ contains information on graphics file formats,
including raster, vector, metafile, PDL, 3D object, animation,
and multimedia formats. It is available on rtfm.mit.edu as
/pub/usenet/news.answers/graphics/fileformats-faq.
Color Space FAQ
Maintained by David Bourgin (david.bourgin@ufrima.imag.fr), the
Color Space FAQ contains questions and answers about colors and
color spaces. It is available on rtfm.mit.edu as
/pub/usenet/news.answers/graphics/colorspace-faq.
Frequently Asked Questions about Gamma and Colour
Charles Poynton has written FAQs on Gamma and Color Spaces. His
FAQs are available from his web page,
http://www.inforamp.net/~poynton/ in a variety of formats. Text
versions may be obtained at ftp.inforamp.net in the
/pub/users/poynton/doc/colour directory.
Computer Graphics Resource Listing
Maintained by Nick Fotis (nfotis@theseas.ntua.gr), the CGRL
contains questions and answers about general graphics
documents, sort of like this document. It came into existence
for political reasons. There is no clear division of
responsibility between his document and mine, but I do tend to
keep this one a bit more terse and free of commercial material.
As a result, the CGRL is much larger and is stored in six
parts. You can get the parts at rtfm.mit.edu as
/pub/usenet/news.answers/graphics/resources-list/part[1-6], or
get the auto-HTMLed version at
http://www.cis.ohio-state.edu/hypertext/faq/usenet/graphics/res
ources-list/top.html.
_________________________________________________________________
General References
BOOKS
* Computer Graphics: Principles and Practice (2nd Ed.), J.D. Foley,
A. van Dam, S.K. Feiner, J.F. Hughes, Addison-Wesley 1990, ISBN
0-201-12110-7
* Procedural Elements for Computer Graphics, David F. Rogers, McGraw
Hill 1985, ISBN 0-07-053534-5
* Mathematical Elements for Computer Graphics (2nd Ed)., David F.
Rogers and J. Alan Adams, McGraw Hill 1990, ISBN 0-07-053530-2
* Fundamentals of Three-Dimensional Computer Graphics, Alan Watt,
Addison-Wesley 1990, ISBN 0-201-15442-0
* An Introduction to Ray Tracing, Andrew Glassner (ed.), Academic
Press 1989, ISBN 0-12-286160-4
* Graphics Gems, Andrew Glassner (ed.), Academic Press 1990, ISBN
0-12-286165-5
* Graphics Gems II, James Arvo (ed.), Academic Press 1991, ISBN
0-12-064480-0
* Graphics Gems III, David Kirk (ed.), Academic Press 1992, ISBN
0-12-409670-0 (with IBM disk) or 0-12-409671-9 (with Mac disk)
* Graphics Gems IV, Paul Heckbert (ed.), Academic Press 1994, ISBN
0-12-336156-7 with MAC floppy, ISBN 0-12-336155-9 with PC floppy
* Digital Image Processing (3rd Ed.), Rafael C. Gonzalez, Richard E.
Woods, Addison-Wesley 1992, ISBN 0-201-50803-6
* A Programmer's Geometry, Adrian Bowyer, John Woodwark,
Butterworths 1983, ISBN 0-408-01242-0 Pbk
* Advanced Animation and Rendering Techniques, Alan Watt, Mark Watt,
Addison-Wesley 1992, ISBN 0-201-54412-1
ERATTA
Errata for "An Introduction to Ray Tracing" is available on
wuarchive.wustl.edu as /graphics/graphics/books/erratas/IntroToRt.
Errata for "Digital Image Warping" is available on wuarchive.wustl.edu
as /graphics/graphics/books/erratas/Digital-Image-Warping.
Errata for "Photorealism and Ray Tracing in C" is available on
wuarchive.wustl.edu as
/graphics/graphics/books/erratas/Photorealism-and-ray-tracing-in-C.
Errata for the "Graphics Gems" series are available on
wuarchive.wustl.edu in /graphics/graphics/books.
OTHER
An automatic mail handler at Brown University allows users of
"Computer Graphics: Principles and Practice," by Foley, van Dam,
Feiner, and Hughes, to obtain text errata and information on
distribution of the software packages described in the book. Also,
users can send the authors feedback, to report text errors and
software bugs, make suggestions, and submit exercises. To receive
information describing how you can use the mail handler, simply mail
graphtext@cs.brown.edu and put the word "Help" in the Subject line.
Use the Subject line "Software-Distribution" to receive information
specifically concerning the software packages SRGP and SPHIGS.
All C code from the "Graphics Gems" series is available via anonymous
ftp from princeton.edu. Look in the directory
pub/Graphics/GraphicsGems for the various volumes (Gems, GemsII,
GemsIII, GemsIV), and get the README file first.
A list of computer graphics, computational geometry and image
processing journals is available from Juhana Kouhia,
jk87377@cs.tut.fi.
_________________________________________________________________
Specific References
RAY-TRACING AND GLOBAL ILLUMINATION
Rick Speer maintains a cross-indexed ray-tracing bibliography. The bib
is in the form of a PostScript file. The printout is 41 pages long. It
may be found on wuarchive.wustl.edu as
/graphics/graphics/bib/RT.BIB.Speer/speer.rt.bib.ps.Z, and on
plaza.aarnet.edu.au as
/graphics/graphics/bib/RT.BIB.Speer/speer.rt.bib.ps.gz.
While useful, this document has not been updated since 1991. Is there
a more recent version out there somewhere that I don't know about?
Ian Ashdown maintains ray tracing and radiosity/global illumination
bibliographies. These are in "refer" format, and so can be searched
electronically (a simple awk script to search for keywords is included
with each). The bibliographies have been combined, and are available
on hobbes.lbl.gov as /pub/doc/RadBib95.Z. There are also some other
interesting papers in the same directory.
Tom Wilson (twilson@dab.ge.com) has collected over 300 abstracts from
ray tracing related research papers and books. The information is
essentially in plaintext, and Latex formatting programs are included.
This collection is available at most of the sites mentioned above as
"rtabs.*".
GRAPHICS FILE FORMATS
* Graphics File Formats, David Kay and John Levine,
Windcrest/McGraw-Hill 1992, ISBN 0-8306-3060-0 $36.95 hardcover,
ISBN 0-8306-3059-7 $24.95 paper. Comments - 26 formats, no
software (this is good, IMHO - I prefer books which are not
platform-dependent). Questions about this book may be sent to
gbook@iecc.cambridge.ma.us.
* Programming for Graphics Files in C and C++, by John Levine, J.
Wiley & Sons, 1994, ISBN 0-471-59854-2 $29.95 softcover. A good
complement to Kay & Levine's book: less text info about the
formats, but working code (IBM PC code) is given for many of the
basic operations for each type of format. Diskette can be ordered
separately.
* Encyclopedia of Graphics File Formats by James D. Murray and
William vanRyper, O'Reilly & Associates, Sebastopol, CA July,
1994, 900 pages, $59.95 (includes a CD-ROM) Softcover ISBN:
1-56592-058-9, Email: orders@ora.com. Good introduction to
graphics file format issues for both vector and raster formats,
plus specific descriptions of nearly 100 file formats. CD-ROM
includes sample images, original format spec documents where
available, and C code snippets. Also a lot of free and shareware
image conversion/manipulation software for Unix, DOS, Windows, and
Mac. Much of this is available on the net (and indeed the book
tells you where), but having it all pulled together is very
useful. Tom Lane (tgl@sss.pgh.pa.us) says: "My only complaint is
that there are too many typos in the printed text. Check the
original spec document whenever you find something unclear or
dubious."
SPATIAL DATA STRUCTURES
* The Design and Analysis of Spatial Data Structures, H. Samet,
Addison-Wesley, Reading, MA, 1990. ISBN 0-201-50255-0.
* Applications of Spatial Data Structures: Computer Graphics, Image
Processing, and GIS, H. Samet, Addison-Wesley, Reading, MA, 1990.
ISBN 0-201-50300-0.
PEX AND PHIGS
* PEXlib Programming Manual, Tom Gaskins, 1154 pages, O'Reilly &
Associates, ISBN 1-56592-028-7
* PEXlib Reference Manual, edited by Steve Talbott, 577 pages,
O'Reilly & Associates, ISBN 1-56592-029-5
* PHIGS Programming Manual, Tom Gaskins, 908 pages, O'Reilly &
Associates, ISBN 0-937175-85-4 (softcover), ISBN 0-937175-92-7
(casebound)
* PHIGS Reference Manual, edited by Linda Kosko, 1099 pages,
O'Reilly & Associates, ISBN 0-937175-91-9
* A Primer for PHIGS, Hopgood, Duce & Johnston, 298 pages, Wiley,
ISBN 0-471-93330-9
There is an analysis of OpenGL vs. PEX, Analysis of PEX 5.1 and OpenGL
1.0, Allen Akin, available on sgi.sgi.com as
/sgi/opengl/doc/analysis.ps.Z.
OPENGL
* OpenGL Programming Guide, Neider, Davis & Woo, Addison-Wesley,
1993
* OpenGL Programming Guide, The Official Guide to Learning OpenGL,
Release 1", Addison-Wesley, ISBN 0-201-63274-8
There is an analysis of OpenGL vs. PEX, Analysis of PEX 5.1 and OpenGL
1.0, Allen Akin, available on sgi.sgi.com as
/sgi/opengl/doc/analysis.ps.Z.
MORPHING
Warping is the deformation of an image by mapping each pixel to a new
location. Morphing is blending from one image or object to another
one. Valerie Hall has written an excellent introduction to warping and
morphing. This is available for anonymous ftp from
marsh.cs.curtin.edu.au in the directory
pub/graphics/bibliography/Morph. There are three files:
* /pub/graphics/bibliography/Morph/morph_intro.ps.Z (PostScript
version, many pictures)
* /pub/graphics/bibliography/Morph/morph_intro.txt.Z (text version)
* /pub/graphics/bibliography/Morph/m_responses.Z (Responses to
morphing questions)
The files are compressed, so you must use binary transfer and
uncompress them afterwards.
The definitive book on the topic:
* Digital Image Warping, George Wolberg, IEEE Computer Society Press
Monograph 1990, ISBN 0-8186-8944-7
RADIOSITY
Radiosity is a technique for generating very realistic scenes using
global illumination (a radiative transfer problem).
* Radiosity and Realistic Image Synthesis, Michael F. Cohen, John R.
Wallace, Academic Press, 1993, ISBN 0-12-178270-0
* Radiosity and Global Illumination, Francois Sillion, Claude Puech,
Morgan Kaufmann, 1994, ISBN 1-55860-277-1
* Radiosity: A Programmer's Perspective, Ian Ashdown, John Wiley &
Sons, 1994, ISBN 0-471-30444-1 (book only), ISBN 0-471-30488-3
(with diskette)
_________________________________________________________________
How do I ...
This section provides brief answers to some of the most frequently
asked how-to questions. More verbose answers can generally be found in
the literature mentioned in the General References section.
HOW DO I DRAW 3D OBJECTS ON A 2D SCREEN?
There are many ways to do this. Some approaches map the viewing
rectangle onto the scene, by shooting rays through each pixel center
and assigning color according to the object hit by the ray. Other
approaches map the scene onto the viewing rectangle, by drawing each
object into the region, keeping track of which object is in front of
which.
The mapping mentioned above is also referred to as a "projection", and
the two most popular projections are perspective projection and
parallel projection. For example, to do a parallel projection of a
scene onto a viewing rectangle, you can just discard the Z coordinate
(divide by depth), and "clip" the objects to the viewing rectangle
(discard portions that lie outside the region).
For details on 3D rendering, the Foley, van Dam, Feiner and Hughes
book, "Computer Graphics: Principles and Practice" would be a good
place to start reading. Chapter 6 is "Viewing in 3D", and chapter 15
is "Visible-Surface Determination". For more information go to chapter
16 for shading, chapter 19 for clipping, and branch out from there.
HOW DO I QUANTIZE 24-BIT IMAGES DOWN TO 8 BITS?
Find a copy of "Color Image Quantization for Frame Buffer Display" by
Paul Heckbert, SIGGRAPH '82 Proceedings, page 297. There are other
algorithms, but this one works well and is fairly simple.
Implementations are included in most raster toolkits (check out the
various free image manipulation software available).
A variant method is described in "Graphics Gems", p. 287-293 (but no
code), and there is further information in "Graphics Gems II", p.
126-133 (code available online but not in book). Spencer Thomas'
article in Gems II on Efficient Inverse Color Map Computation (p.
116-125) is also relevant, and code is provided in the book and
online, as well as in the Utah Raster Toolkit. Note that the code from
the "Graphics Gems" series is all available from an FTP site, as
described above.
Also check out John Bradley's "Diversity Algorithm", which is
incorporated into the xv package and described in the back of the
manual.
The ImageMagick package contains another quantizing algorithm which is
presented as "doing a better job than the other algorithms, but
slower".
Ian Ashdown (Ledalite@mindlink.bc.ca) is maintaining a bibliography of
color quantization papers and articles that is available at
hobbes.lbl.gov as /pub/doc/cquant95.Z. It includes both the original
presentations of the algorithms and their implementation in popular
computer magazines such as Dr. Dobb's Journal and The C/C++ Users
Journal.
HOW DO I CONVERT COLOR TO GRAYSCALE?
The NTSC formula is:
luminosity = .299 red + .587 green + .114 blue
For additional information, please refer to the Color Space FAQ.
HOW DO I CONVERT GRAYSCALE TO BLACK & WHITE?
The definitive book on the topic:
* Digital Halftoning, Robert Ulichney, MIT Press 1987, ISBN
0-262-21009-6
But before you go off and start coding, check out the variety of free
image manipulation software available. Almost all of the packages
mentioned can do some form of gray to b&w conversion.
For additional information, please refer to the Color Space FAQ.
HOW DO I ROTATE A RASTER IMAGE BY AN ARBITRARY ANGLE?
The obvious but wrong method is to loop over the pixels in the source
image, transform each coordinate, and copy the pixel to the
destination. This is wrong because it leaves holes in the destination.
Instead, loop over the pixels in the destination image, apply the
*reverse* transformation to the coordinates, and copy that pixel from
the source. This method is quite general, and can be used for any
one-to-one 2-D mapping, not just rotation. You can add anti-aliasing
by doing sub-pixel sampling.
However, there is a much faster method, with antialising included,
which involves doing three shear operations. The method was originally
created for the IM Raster Toolkit; an implementation is also present
in PBMPLUS. Reference: A Fast Algorithm for Raster Rotation", by Alan
Paeth (awpaeth@watcgl.waterloo.edu) Graphics Interface '86
(Vancouver). An article on the IM Raster Toolkit appears in the same
journal. An updated version of the rotation paper appears in "Graphics
Gems" under the original title.
HOW DO I DRAW A CIRCLE AS A BEZIER (OR B-SPLINE) CURVE?
The short answer is, "You can't." Unless you use a rational spline you
can only approximate a circle. The approximation may look acceptable,
but it is sensitive to scale. Magnify the scale and the error of
approximation magnifies. Deviations from circularity that were not
visible in the small can become glaring in the large. If you want to
do the job right, consult the article:
"A Menagerie of Rational B-Spline Circles" by Leslie Piegl and Wayne
Tiller in IEEE Computer Graphics and Applications, volume 9, number 9,
September, 1989, pages 48-56.
For rough, non-rational approximations, consult the book:
Computational Geometry for Design and Manufacture by I. D. Faux and M.
J. Pratt, Ellis Horwood Publishers, Halsted Press, John Wiley 1980.
For the best known non-rational approximations, consult the article:
"Good Approximation of Circles by Curvature-continuous Bezier Curves"
by Tor Dokken, Morten Daehlen, Tom Lyche, and Knut Morken in Computer
Aided Geometric Design, volume 7, numbers 1-4 (combined), June, 1990,
pages 33-41 [Elsevier Science Publishers (North-Holland)]
HOW DO I TELL WHETHER A POINT IS WITHIN A PLANAR POLYGON?
Consider a ray originating at the point of interest and continuing to
infinity. If it crosses an odd number of polygon edges along the way,
the point is within the polygon. If the ray crosses an even number of
edges, the point is either outside the polygon, or within an interior
hole formed from intersecting polygon edges. This idea is known in the
trade as the Jordan curve theorem; see Eric Haines' article in
Glassner's ray tracing book (above) for more information, including
treatment of special cases.
Another method is to sum the absolute angles from the point to all the
vertices on the polygon. If the sum is 2 pi, the point is inside, if
the sum is 0 the point is outside. However, this method is about an
order of magnitude slower than the previous method because evaluating
the trigonometric functions is usually quite costly.
Code for both methods (plus barycentric triangle testing) can be found
in the Ray Tracing News, Vol. 5, No. 3, available from princeton.edu
as /pub/Graphics/RTNews/RTNv5n3.Z.
This code has been updated and expanded. A long article on the topic
appears in _Graphics Gems IV_ and the code (along with a timing test
program) is available from princeton.edu as
/pub/Graphics/GraphicsGems/GemsIV/GGemsIV.tar.Z.
HOW DO I TESSELLATE A SPHERE?
One simple way is to do recursive subdivision into triangles. The base
of the recursion is an octahedron, and then each level divides each
triangle into four smaller ones. Jon Leech has posted a nice routine
called sphere.c that generates the coordinates. It's available for FTP
on ftp.ee.lbl.gov and princeton.edu.
HOW DO I RAY-TRACE HEIGHT FIELDS?
Height fields are a special case in ray-tracing. They have a number of
uses, such as terrain rendering, and some optimization is possible.
Thus, they get their own FAQ section. Note that further references can
no doubt be located via the ray-tracing bibs in section 16 above.
The following paper seems to be the definitive reference: "Grid
Tracing: Fast Ray Tracing For Height Fields", F. Kenton Musgrave,
July, 1988.
This is available as "Research Report YALEU/DCS/RR-639" from Yale
University, it's also in the SIGGRAPH '91 Fractal Modeling in 3D
Computer Graphics and Imaging course notes, and (best of all) it's
available on the net, at princeton.edu, as
/pub/Graphics/Papers/musg88.ms.Z.
An implementation of this paper may be found in Rayshade.
Another paper exists: "Parametric Height Field Ray Tracing", D. W.
Paglieroni, S. M. Peterson, Proceedings of Graphics Interface '92,
Canadian Information Processing Society, Toronto, Ontario, May 1992,
p. 192-200
And still one more: "The Synthesis and Rendering of Eroded Fractal
Terrains", Musgrave, Kolb, Mace, Computer Graphics Vol 23, No. 3
(SIGGRAPH '89 Proceedings) p. 41-50
HOW DO I FIND THE AREA OF A 3D POLYGON?
The area of a triangle is given by (in C notation)
area = 0.5 * ( ( x[0] * y[1] ) + ( x[1] * y[2] ) + ( x[2] * y[0] ) -
( x[1] * y[0] ) - ( x[2] * y[1] ) - ( x[0] * y[2] ) );
and the area of a planar polygon is given by
area = 0.0;
for ( i = 0; i <n - 1; i++ )
area += ( x[i] * y[i + 1] ) - ( x[i + 1] * y[i] );
area += ( x[n - 1] * y[0] ) - ( x[0] * y[n - 1] );
area /= 2.0;
or, equivalently but more quickly
area = 0.0;
for ( i = 0; i <n - 1; i++ )
area += ( x[i] - x[i + 1] ) * ( y[i + 1] + y[i] );
area += ( x[n - 1] - x[0] ) * ( y[0] + y[n - 1] );
area /= 2.0;
If the area is a negative number, the polygon or triangle is
clockwise, if positive, it is counterclockwise.
From Ronald Goldman's Gem (in Graphics Gems II - see section 1 above),
"Area of Planar Polygons and Volume of Polyhedra:"
The area of a polygon P0, P1, P2, ... Pn, not in the x-y plane, is
given by
Area(Polygon) = 1/2 * | N . Sigma { Pk x Pk+1 } |
where N is the unit vector normal to the plane and P is a polygonal
vertex. The . represents the dot product operator and the x represents
the cross product operator. Sigma represents the summation operator. |
| represents the absolute value operator. Pn+1 is equal to P0.
HOW DO I CONVERT BETWEEN VECTOR FORMATS?
A lot of people ask about converting from HPGL to PostScript, or
MacDraw to CGM, or whatever. It is important to understand that this
is a very different problem from that addressed by the free image
manipulation software below. Converting one image format to another is
a fairly easy problem, since once you get past all the file header
junk, a pixel is a pixel -- the basic objects are the same for all
image formats. This is not so for vector formats. The basic objects --
circles, ellipses, drop-shadowed pattern-filled round-cornered
rectangles, etc. -- vary from one format to another. Except in
extremely restricted cases, it is simply not possible to do a
one-to-one conversion between vector formats.
On the other hand, it is quite possible to do a close approximation,
rendering an image from one format using the primitives from another.
As far as I know, no one has put together a general toolkit of such
converters, but two different HPGL to PostScript converters have been
posted to comp.sources.misc. Check the index on your nearest archive
site.
A related frequent question is how to convert from some vector format
to a bitmapped image - from PostScript to Sun raster format, or HPGL
to X11 bitmap. For example, some of the commercial PostScript clones
for PC's allow you to render to a disk file as well as a printer.
Also, the PostScript interpreters in the NeXT box and in Sun's
X11/NeWs can be used to render to a file if you're clever. But in
general, the answer is no. However, if someone were to put together a
vector to vector conversion toolkit, adding a vector to raster
converter would be trivial.
GNU ghostscript (from the FSF - current version 2.6.1) includes
drivers for both ppm and gif format files, thus it can be used as a
PostScript to ppm or a PostScript to GIF filter. (It implements
essentially all of PostScript level 1 and alot of Display PostScript
and level 2).
There is a package called hp2xx, which includes a fairly nice HP-GL
previewer/converter, and which can convert to several formats,
including PBM. The latest version is hp2xx-3.1.2.tar. It's available
on many archive sites.
HOW DO I GET FILES IF I CAN'T FTP?
There are a number of sites that archive the Usenet sources newsgroups
and make them available via an email query system. You send a message
to an automated server saying something like "send
comp.sources.unix/fbm", and a few hours or days later you get the file
in the mail.
In addition, there is at least one FTP-by-mail server. Send mail to
ftpmail@decwrl.dec.com saying "help" and it will tell you how to use
it. Note that this service has at times been turned off due to abuse.
_________________________________________________________________
Where can I get ...
This section provides information on how to obtain frequently sought
items. I tend to shy away from commercial products other than books so
as to remain as neutral as possible. I don't want to see things like
"... the paint program recommended in the comp.graphics FAQ!" get a
toe-hold in my reality. :-)
WHERE CAN I GET FORMAT DOCUMENTS FOR TIFF, IFF, GIF, ETC.?
You almost certainly don't need these due to the existence of a large
quantity of very good free image manipulation software. Get one or
more of these packages and look through them. Chances are excellent
that the image converter you were going to write is already there.
But if you still want one of the format documents, many such files are
available by anonymous ftp from the following sites:
* zamenhof.cs.rice.edu:/pub/graphics.formats
* ftp.ncsa.uiuc.edu:/misc/file.formats/graphics.formats
* telva.ccu.uniovi.es:/pub/graphics/file.formats
* peipa.essex.ac.uk:/ipa/file-formats
* avalon.vislab.navy.mil:/pub/format_specs
There are many files in each of these directories. Your best bet is to
go there and look around.
FITS stands for Flexible Image Transport System. It's a file format
most often used in astronomy. Despite the name, it can contain not
only images but other things as well. There is a regular monthly FITS
basics and information posting on sci.astro.fits - read it if you want
to know more.
WHERE CAN I GET FREE IMAGE MANIPULATION SOFTWARE?
There are a number of toolkits for converting from one image format to
another, doing simple image manipulations such as size scaling, plus
the above-mentioned 24 -> 8, color -> gray, gray -> b&w conversions.
While there is a full URL listed for many of these packages, this is
really quite misleading. Most of these packages are available from
numerouse sites. I highly recommend two things:
1. Use archie or a similar tool to locate an ftp site close to you,
rather than fighting the frothing hordes for access to wuarchive.
2. ftp to your chosen site manually, change to the directory listed
in the FAQ for your chosen package, and look around. You will
often find newer versions or additional, related files.
That being said, here are the packages:
xv by John Bradley
X-based image display, manipulation, and format conversion
package. XV displays many image formats and permits editing of
GIF files, among others. The latest version is 3.00a, and may
be found at John's site ftp.cis.upenn.edu as
/pub/xv/xv-3.00a.tar.Z.
PBMPLUS by Jef Poskanzer
Comprehensive format conversion and image manipulation package.
It is available at ftp.ee.lbl.gov as /pbmplus10dec91.tar.Z and
at wuarchive.wustl.edu as
/graphics/graphics/packages/pbmplus/pbmplus10dec91.tar.Z.
NETPBM
This is a Usenet community supported version of the PBMPLUS
toolkit, including many new and updated converters. It is
available at wuarchive.wustl.edu as
/graphics/graphics/packages/NetPBM/netpbm-1mar1994.tar.gz. A
mailing list exists as well.
IM Raster Toolkit by Alan Paeth (awpaeth@watcgl.uwaterloo.ca)
Provides a portable and efficient format and related toolkit.
The format is versatile in supporting pixels of arbitrary
channels, components, and bit precisions while allowing
compression and machine byte-order independence. The kit
contains more than 50 tools with extensive support of image
manipulation, digital halftoning and format conversion.
Previously distributed on tape c/o the University of Waterloo,
an FTP version will appear someday.
Ed. Note: This is a very old blurb. Is this kit available on
the net? If so, where? If not, how does one get it? Is it
obsolete?
Utah RLE Toolkit
Conversion and manipulation package, similar to PBMPLUS.
Available via FTP as cs.utah.edu:pub/urt-*,
princeton.edu:pub/Graphics/urt-*, and
freebie.engin.umich.edu:pub/urt-*.
Fuzzy Pixmap Manipulation by Michael Mauldin
Conversion and manipulation package, similar to PBMPLUS.
Version 1.0 available via FTP at network.ucsd.edu as
/graphics/fbm.tar.Z.
Xim (X Image Manipulator) by Philip R. Thompson
It does essential interactive image manipulations and uses
x11r4 and the OSF/Motif toolkit for the interface. It supports
images in 1, 8, 24 and 32 bit formats. Reads/writes and
converts to/from GIF, xwd, xbm, tiff, rle, xim, and other
formats. Writes level 2 postscript. Other utilities and image
application library are included. Not a paint package.
Available at gis.mit.edu as /pub/xim3i.tar.Z.
xloadimage by Jim Frost
Reads in images in various formats and displays them on an X11
screen. Available via FTP as in your nearest comp.sources.x
archive.
xli, by Graeme Gill
This is an updated xloadimage with numerous improvements in
both speed and in the number of formats supported. Available at
ftp.x.org as /contrib/applications/xli.1.16.tar.gz.
TIFF Software by Sam Leffler
Nice portable library for reading and writing TIFF files, plus
a few tools for manipulating them and reading other formats.
Available via FTP as sgi.com:graphics/tiff/*.tar.Z.
xtiff This is an X11 tool for viewing a TIFF file. It was written to
handle as many different kinds of TIFF files as possible while
remaining simple, portable and efficient. xtiff illustrates
some common problems with building pixmaps and using different
visual classes. It is distributed as part of Sam Leffler's
libtiff package and it is also available on ftp.uu.net and
comp.sources.x. xtiff 2.0 was announced in 4/91; it includes
Xlib and Xt versions.
ALV This is a Sun-specific image toolkit. Version 2.0.6 was posted
to comp.sources.sun on 11dec89. Also available via email to
alv-users-request@cs.bris.ac.uk.
popi This is an image manipulation language. Version 2.1 posted to
comp.sources.misc on 12dec89.
ImageMagick
This is an X11 package for display and interactive manipulation
of images. Includes tools for image conversion, annotation,
compositing, animation, and creating montages. ImageMagick can
read and write many of the more popular image formats.
Available from ftp.x.org as
/contrib/applications/ImageMagick/ImageMagick-3.3.tar.gz.
Khoros
This is a huge (~100 meg) graphical development environment
based on X11R4. Khoros components include a visual programming
language, code generators for extending the visual language and
adding new application packages to the system, an interactive
user interface editor, an interactive image display package, an
extensive library of image and signal processing routines, and
2D/3D plotting packages. Available at ftp.eece.unm.edu as
/pub/khoros/*. A newsgroup exists for the discussion of khoros
and khoros-related topics, comp.soft-sys.khoros.
LaboImage
This is a SunView-based image processing and analysis package.
It includes more than 200 image manipulation, processing and
measurement routines, on-line help, plus tools such as an image
editor, a color table editor and several biomedical utilities.
Available via anonymous FTP on nic.funet.fi in
/pub/graphics/packages.
The San Diego Supercomputer Center Image Tools
These are software tools for reading, writing, and manipulating
raster images. Binaries for some machines are available at
sdsc.edu as /pub/sdsc/graphics/imtools/*.
Independent JPEG Group's free JPEG software
The Independent JPEG Group has written a package for reading
and writing JPEG files. FTP to
ftp.uu.net:graphics/jpeg/jpegsrc.v?.tar.gz
bit (Bitmap Image Touchup) by T.C. Zhao
This is a full color viewer/editor with a variety of features.
SGI only. It may be obtained via FTP at monte.svec.uh.edu in
/pub/bit.
"Libreria de Utilidades Graficas" or "Graphic Utilities Library"
This is a library of subroutines for image manipulation. It has
routines for loading, viewing and manipulationg a variety of
formats. It may be obtained at ftp.uniovi.es as
/uniovi/mathdept/src/liblug.tar.gz.
Dore' (Dynamic Object Rendering Environment)
Dore' is a powerful 3D graphics subroutine library. It provides
a comprehensive set of tools for creating graphics
applications. It is also easy to use, portable, and extendable.
This version has interfaces/drivers to X11, PEX, IrisGL,
OpenGL, Postscript and more. It is known to run on NetBSD 1.0,
Linux, FreeBSD, Solaris 2.3, and OSF/1. It has also been ported
to Windows NT 3.5. The official distribution site is
sunsite.unc.edu, where it may be found in
pub/packages/development/graphics/Dore as pdore-6.0.tar.Z.
XMegaWave
XMegaWave is a graphics window environment oriented to image
processing. It is based in the collaboration between
researchers from the University of Balear Islands (U.I.B.), The
University of Las Palmas (U.L.P.G.C.) and the University of
Paris IX Dauphine (U.P.D.). XMW is oriented to UNIX
workstations which work with X11R4 and Motif1.1 libraries (this
XMW version). Currently, it is available for HP-Apollo and SGI
workstations. Full source is not available as of yet, but the
authors say they will cooperate in getting other versions
built. XMW may be obtained on ftp.dis.ulpgc.es in the
/investigacion/ami/XMegaWave directory.
Please do *not* post or mail messages saying "I can't FTP, could
someone mail this to me?" There are a number of automated mail servers
that will send you things like this in response to a message. Refer to
the section of this document titled How do I get files if I can't ftp?
for more help.
Also, the newsgroup alt.graphics.pixutils is specifically for
discussion of software like this. You may find useful information
there.
WHERE CAN I GET FREE PLOTTING SOFTWARE?
Gnuplot is a command-driven interactive data/function plotting
program. It runs on just about any machine, and is very flexible in
terms of supported output devices. The official North American
distribution site for the latest version is dartmouth.edu in
/pub/gnuplot. More information is available from the USENET newsgroup
comp.graphics.gnuplot and its FAQ, graphics/gnuplot-faq.
ACE/gr (xmgr - Motif/xvgr - XView) is a data/function plotting tool
for workstations or X-terminals using X. Available from
ftp.ccalmr.ogi.edu in /CCALMR/pub/acegr.
robotx (Robot) is a general purpose plotting and data analysis
program. Requires XView, X-terminal or workstation. Available from
sunsite.unc.edu in /pub/academic/data_analysis.
Xgraph is a popular two-dimensional plotting program that accepts data
in a form similar to the unix program graph and displays line graphs,
scatter plots, or bar charts on an X11 display. Available from
ic.berkeley.edu in /pub.
Drawplot is a program for drawing 2D plots on X10/X11 windows, SUNVIEW
displays, or HP2648 terminals. Available from xcf.berkeley.edu in
/src/local.
WHERE CAN I GET STANDARDS DOCUMENTS?
The American National Standards Institute sells ANSI standards, and
also ISO (international) standards. Their sales office is at
1-212-642-4900, mailing address is 1430 Broadway, NY NY 10018. It
helps if you have the complete name and number.
Some useful numbers to know:
* CGM (Computer Graphics Metafile) is ISO 8632-4 (1987)
* GKS (Graphical Kernel System) is ANSI X3.124-1985
* PHIGS (Programmer's Hierarchical Interactive Graphics System) is
ANSI X3.144-1988
* IGES is ASME/ANSI Y14.26M-1987
Language bindings are often separate but related numbers; for example,
the GKS FORTRAN binding is X3.124.1-1985.
Standards-in-progress are made available at key milestones to solicit
comments from the graphical public (this includes you!). ANSI can let
you know where to order them; most are available from Global
Engineering at 1-800-854-7179.
WHERE CAN I GET 3D OBJECTS?
So far, I know of only one really large clump of them on the net. It
is located at avalon.vislab.navy.mil. The site administrators request
that major downloads be kept to non-peak hours. Their official mirror
site is ftp.kpc.com.
WHERE CAN I GET MRI AND CT SCAN VOLUME DATA?
Volume data sets are available from the University of North Carolina
at omicron.cs.unc.edu (152.2.128.159) in /pub/softlab/CHVRTD.
(Commercial use is prohibited.)
* Head data - A 109-slice MRI data set of a human head.
* Knee data - A 127-slice MRI data set of a human knee.
* HIPIP data - The result of a quantum mechanical calculation of a
SOD data of a one-electron orbital of HIPIP, an iron protein.
* SOD data - An electron density map of the active site of SOD
(superoxide dismutase).
* CT Cadaver Head data - A 113-slice MRI data set of a CT study of a
cadaver head.
* MR Brain data - A 109-slice MRI data set of a head with skull
partially removed to reveal brain.
* RNA data - An electron density map for Staphylococcus Aureus
Ribonuclease.
WHERE CAN I GET MPSC AND AOEGA INFO?
The Motion Picture Screen Cartoonists and Affiliated Optical
Electronic and Graphic Arts, Local 839 IATSE is pleased to announce
the availability by anonymous FTP of information files about our
organization.
Local 839 IATSE is the largest local union of motion picture graphic
artists in the world. We have over 1,500 active members employed in
animation and CGI in Southern California.
These files are available at ftp.netcom.com:/pub/mp/mpsc839 via
anonymous ftp.
For further information, contact them at mpsc839@netcom.com.
_________________________________________________________________
Graphics-related Mailing Lists
There are a variety of graphics-related mailing list out there, each
covering either a single product or a single topic. I have been an
active participant in several of these for some time now, and find the
focus and expertise which can be brought to bear on an isolated topic
to be nothing short of amazing.
Please send corrections if you notice outdated or erroneous
information in this list! Also, feel free to send me any other lists
you would like to see added.
IMAGINE MAILING LIST
The Imagine mailing list provides a discussion forum for users of the
Imagine 3D Rendering and Animation package from Impulse. Currently,
Imagine runs on the Amiga and the PC.
To subscribe, send mail to imagine-request@email.sp.paramax.com with
the word "subscribe" in the subject line.
DCTV MAILING LIST
The DCTV mailing list provides a discussion forum for users of the
Digital Creations DCTV box, software, and file formats. DCTV is an
Amiga graphics module.
To subscribe, send mail to DCTV-request@nova.cc.purdue.edu with the
word "subscribe" in the subject line.
RAYSHADE USERS MAILING LIST
The Rayshade Users mailing list provides a discussion forum for users
of the Rayshade raytracer. Rayshade is a public domain raytracer, with
source available on the net. It runs on most Unix boxes, as well as
the Amiga, Mac and PC platforms. To subscribe, send mail to
rayshade-request@cs.princeton.edu with the word "subscribe" in the
subject line.
LIGHTWAVE MAILING LIST
The Lightwave mailing list provides a discussion forum for users of
the Lightwave 3D Rendering and Animation package from Newtek.
Currently, Lightwave runs on the Amiga, but it will soon be available
on various other platforms.
To subscribe, send mail to lightwave-request@bobsbox.rent.com with the
"subscribe lightwave-l address" in your message.
VIDEO TOASTER MAILING LIST
The Video Toaster mailing list provides a discussion forum for users
of the Video Toaster product from Newtek. The Video Toaster is an
Amiga board which includes Lightwave and a lot of video functionality.
To subscribe, send mail to toaster-request@bobsbox.rent.com with
"subscribe toaster-l address" in your message.
MAILING LIST FOR MASSIVE PARALLEL RENDERING
This list title seems pretty self-explanatory. I believe it is
primarly a Unix-oriented list.
To subscribe, send mail to mp-render-request@icase.edu with the word
"subscribe" in the subject line.
NETPBM MAILING LIST
The Netpbm mailing list provides a discussion forum for the
net-supported netpbm package. I believe this to be largely a developer
forum. Netpbm runs on just about any platform you could name.
To subscribe, send mail to oliver@fysik4.kth.se with the word
"subscribe" in the subject line.
POV-RAY MAILING LIST
The POV-Ray mailing list provides a discussion forum for users of the
POV-Ray raytracer. POV-Ray is a public domain raytracer, with source
available on the net. It runs on most Unix boxes, as well as the
Amiga, Mac and PC platforms. To subscribe, send mail to
listserv@vm3090.ege.edu.tr with "subscribe dkb-l" in the subject line.
RAYDREAM MAILING LIST
The Ray Dream mailing list provides a discussion forum for users of
the Ray Dream Rendering and Animation package. Currently, Ray Dream
runs only on the Mac.
To subscribe, send mail to listserv@cornell.edu with "subscribe
raydream-l address" in your message.
COMPUTATIONAL GEOMETRY MAILING LIST
The Computational Geometry mailing lists are meant for those working
or interested in computational geometry. There are actually three
separate but related lists:
* compgeom-announce: for announcements about professional activities
* compgeom-discuss: for discussion or questions
* compgeom-tribune: a newsletter in LaTeX.
To subscribe to one of these lists, send mail to
compgeom-request@research.att.com with the message "subscribe xxxx" in
the message body or subject line, where xxxx is the name of one of the
three lists.
The compgeom list also provides some other neat stuff, such as a
bibliographic search service. Send mail to
compgeom-request@research.att.com with the message "send readme" for
more information.
PHOTOSHOP MAILING LIST
The Photoshop mailing list provides a discussion forum for users of
the Photoshop image conversion and manipulation package from Adobe.
Adobe Photoshop runs on Windows, Macintosh, and SGI platforms. The
latest version, 3.0, does not work properly under OS/2 and Adobe
refuses to address the problem (editorial comment).
To subscribe, send mail to photshop@bgu.edu with "subscribe" in the
body of your message.
3DSTUDIO MAILING LIST
The 3dstudio mailing list provides a discussion forum for users of the
3D Studio modelling and rendering package from Autodesk. Autodesk 3D
Studio runs only on the PC platform, AFAIK.
To subscribe, send mail to majordomo@autodesk.com with "Subscribe
3dstudio &LTaddress&GT" in the body of your message. The &LTaddress&GT
section is optional, and should not include the &LT&GT.
KPT MAILING LIST
The KPT mailing list provides a discussion forum for users of Kai's
Power Tools, a set of cool texture plugins for Adobe Photoshop and
other packages. Kai's Power Tools work on Windows and the Mac.
To subscribe, send mail to listserv@netcom.com with "subscribe
kpt-list" in the body of your message.
KODAK PHOTO CD MAILING LIST
The KODAK Photo CD mailing list is a public mailing list for
discussion of the Photo CD format and related topics.
To subscribe, send mail to listserv@info.kodak.com with the command
"SUBSCRIBE PHOTO-CD &LTfirst-name&GT &LTlast-name&GT", substituting
your own first and last names in the obvious spots. Both these names
and the address you subscribe from will be used by the mailing list
software.
CALIGARI TRUESPACE MAILING LIST
The Caligari mailing list provides a discussion forum for users of the
Caligari TrueSpace Rendering and Animation package from Caligari. I
believe Caligari currently runs on the Amiga and PC (Windows)
platforms.
To subscribe, send mail to truespace-request@cs.uregina.ca with
"subscribe" in your message.
GLOBAL ILLUMINATION MAILING LIST
The Global Illumination mailing list is a forum for the discussion of
research issues pertaining to the simulation of 'global illumination',
that is the balance of radiant energy between a set of surfaces of
radiatively active media. This is not a list for the newbie or the
dabbler - 75% of the current members are researchers in academic
environments.
To subscribe, send a message to globillum-request@imag.fr containing
your name, affiliation, and 2 lines describing your interests.
_________________________________________________________________
SIGGRAPH
SIGGRAPH, the Special Interest Group for Graphics of the Association
for Computing Machinery, is the premiere professional organization in
the computer graphics world. It is so active and so pervasive that I
feel it deserves its own section.
SIGGRAPH INFORMATION ONLINE
ACM-SIGGRAPH provides an online information site at siggraph.org
(128.248.245.250). This site provides SIGGRAPH information via both
anonymous ftp and an electronic mail archive server.
The anonymous ftp service is very standard, and the ftp directory
includes both conference and publications subdirectories.
To retrieve information by electronic mail, send mail to
archive-server@siggraph.org and in the subject or the body of the
message include the message send followed by the topic and subtopic
you wish. A good place to start is with the command send index which
will give you an up-to-date list of available information.
The coolest way to get SIGGRAPH info, of course, is via their WWW page
at http://www.siggraph.org.
HOW TO JOIN ACM/SIGGRAPH
Probably the easiest way to join ACM/SIGGRAPH is to trot over to your
local technical library and find a copy of Communications of the ACM.
Somewhere within the first few pages will be an application blank.
Fill it out and mail it in. ACM membership for students costs $24.00,
Voting or Associate Membership $79.00 (yearly).
SIGGRAPH student membership costs an additional $50.00, $59.00 for
Voting or Associate Members (also yearly). To get TOG (Transactions on
Graphics) it's another $27.00 for students and $32.00 for Voting or
Associate Members (TOG is an ACM publication, not a SIGGRAPH
publication).
If you just want to join SIGGRAPH without joining ACM, it'll cost you
$85.00 (no student discount).
There are surcharges for overseas airmailing of publications.
ACM Member services may be contacted via email at
acmhelp@acmvm.bitnet. Their phone number is (212) 626-0500. FAX number
(212) 944-1318. Snailmail address ACM, PO Box 12114, Church Street
Station, NY, NY 10257
SIGGRAPH `95 will be held in Los Angeles, California, August 6-11,
1995.
SIGGRAPH ONLINE BIBLIOGRAPHY PROJECT
The ACM SIGGRAPH Online Bibliography Project is a database of over
15,000 unique computer graphics and computational geometry references
in BibTeX format, available to the computer graphics community as a
research and educational resource.
The database is located at "siggraph.org". Users may download the
BibTeX files via FTP and peruse them offline, or telnet to
"siggraph.org" and log in as "biblio" and interactively search the
database for entries of interest, by keyword.
Web users may also access the SIGGRAPH Online Bibliography Project via
the URL http://www.siggraph.org
http://siggraph.org/library/bibliography/bibliography.html.
Additions/corrections/suggestions may be directed to the admin,
"bibadmin@siggraph.org".
_________________________________________________________________
Check out John Grieggs' Home Page
_________________________________________________________________
grieggs@netcom.com / grieggs@primenet.com / JohnG@cup.portal.com
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