Archive-name: graphics/animation-faq
Last-modified: 20 Jan 1995
Version: 2.2
Posting-frequency: Monthly
Last-issue: comp.graphics.animation FAQ v2.1 (25 nov)
Anyone interested in taking over the maintenance of the FAQ or any
of the chapters, please step forward. See To Do for more information.
You've come this far, you may as well read the introduction...
Introduction
************
Please read this faq before posting to `comp.graphics.animation'.
Computer animation is a large and growing field, and people want
different things from it; this FAQ tries to cover all bases, and as a
result is rather thin on many of them! So feel free to contribute, or
to offer suggestions -- the FAQ will *never* be complete or free of
errors, but your help will make it better.
In this (introductory) chapter, we try to give some guidelines on
posting to `comp.graphics.animation', and deal with some matters
concerning the FAQ document itself.
In *Related Resources*, we look at related newsgroups, define some
conventions for resource references in this document, and point to some
general resources that may be of use.
In *Using Animation*, we cover animation file formats, animation
players, and point to some sites where animation may be found.
In *Hobby Animation*, we give an overview of the stages in the
animation process, and note some venues for computer animation.
*Animation Media* tries to cover the various forms an animation may
end up in, and how to get there and back again.
*Career Animation* is intended for those who want to make a living
out of animation, and *Animation Theory* is intended for those
interested in the internals of computer animation packages, and the
research behind them.
The *Animation Software* chapter is cheifly a list of available
computer animation packages, including pointers to net resources
specific to those packages, and to wrap up is *Miscellaneous*.
Changes
=======
Practically nothing has changed since the last posting two months
ago. My apologies both for the tardiness of this posting, and the lack
of improvement. See To Do for how you can help!
* the alias web site
* RCS-Revelation 3d and RCS-Animator Broadcast now correctly under
Vision Images. Also new details for animator broadcast.
* new newsgroup `comp.graphics.rendering.renderman'
Should I Post to comp.graphics.animation?
=========================================
`comp.graphics.animation' is a forum for discussion of all things
relating to computer animation. This includes, but is not limited to
the following. Please remember that these are not hard-and-fast-rules,
simply guidelines. (If there are any glaring omissions here, someone
please point them out to me.)
* computer animation research
* implementation of animation systems
* animation software packages
* animation-related hardware
* computer animation in film and tv
* working in the animation industry
* net-accessible animation
If your post is not of general interest (to
`comp.graphics.animation'), but you think `c.g.anim' is the most
specific, the most appropriate, or is likely to be the most fruitful
forum -- don't hesitate to post. But `c.g.anim' is not for discussion
of things for which there *are* more specific resources available (ie
newsgroups, mailing lists, etc) and which are not of *general interest*
(to `c.g.anim' readers). Ie: if it happens that there is a mailing
list for the package that you're having problems with, mail to it
before posting to `c.g.anim'; if you want to know how to implement
double-buffering on your video card, and there's a newsgroup
specifically about video cards on your machine, use it, not `c.g.anim'.
If you're not sure, you may as well post -- the group's not
moderated, and is frequented by mostly polite people -- you're not
likely to get flamed, but please do spare a moment's thought before you
post.
The next chapter (see Related Resources) lists some places you may
find more suited to your particular query.
Availability / Distribution
===========================
I can now easily generate plain-text (ASCII), HTML, DVI, PostScript,
GNU Info, and AmigaGuide versions of this FAQ (see see Creating this
FAQ), although external links from the HTML document aren't properly
implemented yet.
The plain-text version of the FAQ is available once a month on
comp.graphics.animation, and the post (like all other `official' FAQs)
is archived on `rtfm'
.
All official FAQs, and then some, are available on the WWW
.
Some of these are plain text, some are not.
The FAQ in the above formats is available by FTP in
`ftp://godzilla.cgl.rmit.edu.au/pub/angus/cga-faq/'.
The HTML version is available via WWW
or alternatively
. A slightly
different HTML version is
.
There are active URLs in this version, but many (the partial ones) are
bogus (the two versions should soon be the same now that links work
properly in my HTML version).
To Do
=====
The FAQ needs a new maintainer or maintainers: I'm currently
finishing off my Master's, and then I'll be overseas for at least six
months. I haven't done any work on the FAQ for the last two months,
(ie since November) and (unsurprisingly) it's suffering. It's likely
that the earliest I'll be able to pick it up again is in October 1995.
What I'd like to see is someone pick up the FAQ where I've left off,
rather than starting all over again from scratch, but anything's better
than nothing! It's possible that no-one wants to take on the *whole*
FAQ, so anyone who's willing to take on just one chapter please make
yourself known. In the case of many maintainers, it may be easier if
the FAQ is split up, and the chapters go their own ways. I don't mind.
I don't care if the format and content of the FAQ are completely
changed by the new maintainer(s). What I don't want to see is no
progress on resources for this group between now and when I return.
Get in touch with me, and we'll work something out.
New sections needed (these are definitely FAQs):
* animation schools
* i wanna be an animator, how do i go about it?
* how much should i charge?
Sections that need a lot of work:
* venues, conferences and events
* animation media chapter (incl. i/o h/w)
* animation theory chapter (esp. references)
* career animation chapter
Related Resources
*****************
or, does my post really belong in `comp.graphics.animation'?
Computer animation, like its progenitor computer graphics, abuts on a
large number of fields. If everyone from all related fields posted
here, the newsgroup would be swamped with irrelevance. The following
sections indicate where your comments, information, or questions might
be better directed. Of course, if `comp.graphics.animation' really
*is* the most appropriate group -- post away!
Newsgroups
==========
Read these groups' FAQs before posting to them -- don't be
flamebait. DO NOT post animations to `comp.graphics.animation' -- a
pointer to some remote access site (for FTP retrieval, etc) is much
better, or use one of the `alt.binaries.pictures*' newsgroups if you
must post.
comp.graphics : image generation, modelling
comp.graphics.algorithms : algorithms for graphics
comp.graphics.raytracing : bouncing light around
comp.graphics.visualisation : scientific / data visualisation
alt.movies.visual-effects : SFX for film and TV
comp.graphics.XXX : \
comp.sys.XXX.graphics : \
comp.sys.XXX : } how do I do YYY
comp.sys.XXX.hardware.video : } on/under XXX
comp.os.ms-windows.* : /
comp.windows.* : /
comp.soft-sys.wavefront : wavefront graphics software
comp.graphics.packages.alias : graphics software from alias research
comp.graphics.packages.lightwave: animation software from NewTek
comp.graphics.rendering.* : only renderman at the moment
comp.multimedia : sound and text and vision
alt.3d : SIRDS, holograms, etc. 3d perception.
rec.arts.{anim*,disney} : discussion of anim pieces (mostly trad)
alt.animation.warner-bros : chuck jones and mates
fj.rec.animation : discussion of anime (in japanese)
alt.graphics.pixutils : picture manipulation, conversion
alt.binaries.pictures* : posts of pictures and anims, formats...
rec.video.{desktop,production} : video, desktop video
sci.image.processing : sophisticated image manipulation
sci.virtual-worlds* : anything about VR
comp.compression : compression issues (incl. JPEG, MPEG)
*.test (misc.test, etc.) : test postings (some people...)
Internet Resources
==================
URLs
----
A URL is a Uniform Resource Locator. URLs are an artifact of the
World Wide Web (WWW), and are how the WWW is connected together -- any
reference to a document or other resource on the WWW is via a URL. As
it's an OK format, and WWW use is becoming more widespread, most
references to net resources in this FAQ are in a URL-like format. Many
of these may actually be URLs (further explanation soon).
If you find a reference in this document that is incorrect or simply
unreachable, please inform me so that others do not have to suffer the
same problems. I can't check every reference in every issue. Without
your help, it's inevitable that the FAQ will be full of bogus
references that are of little help to anyone.
HTML URLs
---------
HTML (hypertext markup language) documents are the ones that WWW
likes best, allow the inclusion of `inline' images and further URLs,
and are formatted on the fly to best fit your Web browser. References
to WWW HTML documents look like the following.
http://site/path/document
http://www.crs4.it/~luigi/MPEG/mpegfaq.html
^www-site ^path ^hypermedia-document
FTP URLs
--------
References to anonymously FTP-able files look like the following.
ftp://site/path/document
ftp://avalon.chinalake.navy.mil/pub/format_specs/iffspecs.lzh
^ftp-site ^path ^document
`/pub' at the root of the path is often assumed. Some FTP
references I give in this document are incomplete, indicating a
directory to browse in or whose whole contents are relevant, or some
degree of uncertainty. (These have a trailing slash ('/'), ellipsis
('...'), or Unix-style wildcards.) Many FTP-able files are mirrored on
other sites to reduce bandwidth; use `archie' to find a copy near you.
FAQ pseudo-URLs
---------------
I don't know of an FAQ URL, so these are pseudo-URLs. References to
FAQs in this document look like the following.
faq://archive-path-and-name
faq://graphics/resources-list/part[1-3]
^archive-path ^archive-name
The `archive-path-and-name' is taken directly from the
`Archive-name:' field in the FAQ's header. All `official' FAQs are
cross-posted to `news.answers', and archived for anonymous FTP on
`rtfm.mit.edu' (and other sites), under the directory
`/pub/usenet/news.answers/', using their archive name. So
`faq://archive-path-and-name' is really shorthand for
`ftp://rtfm.mit.edu/pub/usenet/news.answers/archive-path-and-name'.
This FAQ is `faq://graphics/animation-faq', or
`ftp://rtfm.mit.edu/pub/usenet/news.answers/graphics/animation-faq',
and our example above (expanding the wildcard (`[1-3]') as we go)
becomes
`ftp://rtfm.mit.edu/pub/usenet/news.answers/graphics/resources-list/part1',
etc. Most multi-part FAQs have a whole directory dedicated to them,
which is indicated with a trailing slash ('/'):
`faq://graphics/resources-list/'
Note that almost all FAQs (official or otherwise) are also available
through Thomas A. Fine's excellent `Usenet FAQs' WWW site
.
Try expanding `faq://archive-path-and-name' as
`http://www.cis.ohio-state.edu/hypertext/faq/usenet/archive-path-and-name/faq.html'.
pseudo-FAQ pseudo-URLs
----------------------
Some FAQ posts are not yet `official' so they won't have an archive
name, and you won't be able to find them on `rtfm'. These I reference
using the following pseudo-URL format.
post://newsgroup/"title"
post://comp.graphics/"Computer Graphics Resource Listing"
^newsgroup ^title (minus date,part,group info,...)
To follow these references, you'll have to look in the appropriate
newsgroup.
Note that almost all FAQs (official or otherwise) are also available
through Thomas A. Fine's excellent `Usenet FAQs' WWW site
.
Mailing List pseudo-URLs
------------------------
References to mailing lists are pseudo-URLs, and look like the
following.
mail://address/subject/"body"
mail://listserv@netcom.com//"subscribe animaster-l"
^who to mail to ^what to put in the message body
Note that the second (subject) field is often blank (as it is in this
example), as is the third (message body) field.
General Resources
=================
These references are specific sources of information in various broad
areas relevant to this FAQ.
`faq://graphics/faq'
The `comp.graphics' FAQ: graphics references, groups, standards,
various algorithms...
Maintained by John T. Grieggs `'. Thanks John!
`faq://graphics/resources-list/part[1-3]'
The `comp.graphics' resource listing: FTP sites, rendering, 3d
modellers, GUIs, visualisation, image analysis, textures...
Maintained by Nikolaos C. Fotis `'. Thanks
Nick!
`faq://graphics/algorithm-faq'
The `comp.graphics.algorithms' FAQ: graphics algorithms in
abundance.
Maintained by Jon Stone `'. Thanks Jon!
`faq://graphics/animation-faq'
This! The `comp.graphics.animation' FAQ: animating, playing
anims, animation "theory", references, fun!
`http://www.lightside.com/~dani'
3DWEB : an animation WWW
site. Animation % hyphenating this causes troubles... industry
resumes (submit yours!) and job offers, information on CGI
production houses. Literature, references, discussion for
animation (not just computer animation). Also images, animations,
other sites. Information on relevant hardware and software firms,
software packages. Pointers to CGI organisations, laboratories,
projects, and some VR pointers.
Maintained by Daniele Colajacomo `'. Thanks
Daniele!
`faq://graphics/fileformats-faq'
The `comp.graphics' file formats FAQ.
Maintained by James D. Murray `'. Thanks James!
`http://www.cinenet.net/GWEB'
GWEB : An informal trade journal
for the computer animation industry. Includes monthly interviews
with industry luminaries, job postings, and information on
production houses. Also information on relevant hardware and
software.
Maintained by Rob and Sharil `'. Thanks!
`http://mambo.ucsc.edu'
mambo : facial animation
`ftp://avalon.chinalake.navy.mil/pub/'
This FTP site is dedicated to things graphical, and is primarily a
stockpile of 3d objects in various formats. It's mirrored at
kubota `ftp.kpc.com'
Maintained by Francisco X. Dejesus
`'. Thanks Francisco!
More Specific Resources
=======================
More specific resources are scattered throughout the FAQ in the
sections dealing with the specific topic, so for instance for resources
concerning animation file formats, see Animation File Formats, and for
resources concerning individual software packages, see Animation
Software.
Using Animation
***************
This chapter's for those who simply want to see the results of
others' hard labour -- animation file formats and conversions, animation
players and sites.
Animation File Formats
======================
[text by mark podlipec and others]
For code that reads: DL, FLI, FLC, GIF, IFF, MovieSetter, PFX,
Quicktime, and RLE animation formats, see the `xanim' entry in Players,
below. Other players' source may also be useful for these and other
formats.
See also: Murray, Vanryper, "Encylopedia of Graphics File Formats",
O'Reilly & Assoc, 1994, ISBN 1565920589. It covers most 2-d and 3-d
graphics file formats out there today.
AVI (PC):
Resources: `ftp://ftp.microsoft.com/...' (RIFF AVI format. doesn't
include compression format).
DL:
FLI, FLC (Autodesk) (PC): FLI support is for 320x200 images, and is
a series of images and deltas. The colour map can be changed during
the animation. FLC has a few additional chunks and supports larger
image sizes.
Resources: FLC article in DDJ'93 - `ftp://simtel20.../graphic/...'; and
on avalon
(specification of format).
GIF (PC): A GIF file consists of a screen colour map and a series of
images, each with an optional colour map. The images don't have to be
at the origin and can be any size smaller than the screen size. This
allows GIF animations to be created that only update the part of the
screen that changes.
Resources: see `faq://graphics/faq'.
IFF ANIM (Amiga): The Amiga's IFF format was designed as a universal
(extensible) data format. Many different data types and chunks can be
found in IFF ANIMs. Many ANIMs include sound chunks or colour cycling.
There are a plethora of compression techniques (with different
tradeoffs) used. Most IFF ANIMs are meant to be double-buffered, with
deltas applying to frames two distant. A looping ANIM means the last
two deltas produce images that are the same as the first two. The
Amiga has a large number of display modes (a couple of them, EHB and
HAM are unusual; HAM is the hardest to emulate.)
Resources: on avalon
(specification of format).
MovieSetter (GoldDisk) (Amiga): A very flexible animation format.
Animations are stored as a bunch of backgrounds, sounds and sets. Sets
are smaller images that get placed on top of the background (with
transparent pixels). A frame list at the end describes each frame.
Each frame specifies which background to use (backgrounds can also
scroll in different directions and speeds), and a list of sets to put on
that background with depth information so characters can pass behind or
in front of each other. Sound information is contained here as well to
sync it up to the action. There is also colour cycling and specialty
fades and wipes. Can come as one file or as three directories and a
control file.
MPEG (lossy):
Resources: `faq://graphics/mpeg-faq', also in germany
`ftp://ftp.cs.tu-berlin.de/pub/msdos/dos/graphics/mpegfa??.zip' (covers
specification, future, software (players, &c), hardware, incl. pointers
to other information...);
`post://alt.binaries.pictures.utilities/"WHERE TO GET MPEG UTILS"';
Luigi's MPEG FAQ ;
another WWW MPEG site ;
`ftp://ftp.crs4.it' (MPEG, and other image compression techniques).
PFX (PageFlipper Plus F/X) (Amiga): A series of deltas with a play
list at the end. Supports colour map changes, nested loops and dynamic
timing.
RLE (URT) (Unix): One or more runlength encoded images, viewable
with an X11 viewing program. Tools for creating consistent colour maps
and for many other operations are part of the toolkit.
Players
=======
`display' v1.84 (PC) (Jih-Shin Ho). AVI, DL, FLC, GL, MPEG.
`ftp://nctuccca.edu.tw/PC/graphics/disp*' (also on `simtel20')
MPEG players for IBM, Mac, Unix, VMS, Next.
See
`post://alt.binary.pictures.utilities/"WHERE TO GET MPEG UTILS"',
MPEG player for Atari, X11, IBM
here
`xanim' (X-Windows) (Mark Podlipec).
DL, FLI, FLC, GIF, IFF, MovieSetter, PFX, Quicktime, RLE
Official FTP site:
`ftp://ftp.x.org/contrib/applications/xanim???.tar.Z'.
WWW page .
DFV
from the same person who gave you DTA (Dave's Targa Animator),
comes Dave's Flic Viewer (?). Available in
`ftp://ftp.povray.org/pub/povray/utilities'
Anim-Format Conversion
----------------------
*Mainactor* (for Amiga) available on Aminet (in `gfx/edit', will
read 14 formats including GIF, IFF-ILBM, IFF-ANIM[5,7,8], MPEG, FL[CI],
and write most of these (not GIF or MPEG) You can add sound effects and
edit your animations too.
Autodesk *Animator* (for PC) will play and convert IFF ANIMs to
FLI/FLC anims.
This section could do with a few more entries.
Animation Sites
===============
`ftp://ftp.univ-rennes1.fr/Images/ASTRO/anim/'
Space anims
`ftp://ftp.cnam.fr/Fractals/anim/'
Fractal anims
`http://w3.eeb.ele.tue.nl/mpeg/index.html'
here : Various MPEG
anims
`ftp://ftp.wustl.edu/pub/aminet/gfx/anim/Kinetic.lha'
here :
Various Amiga anims (also on other aminet sites)
`ftp://ftp.povray.org'
POV-anims
`http://www.cs.ubc.ca/nest/imager/imager.html'
here : mpeg
animations done using hierarchical b-splines More on the modeller
in See Dragon.
Mat Carr's animations
Find them here
.
Red's Nightmare (a ray-traced animation)
Here:
.
"Grinning Evil Death" (featuring a cockroach and a breakfast cereal
superhero) and other computer animation is available in video stores as
"The Computer Animation Festival, Volume 1".
See 3DWEB for more sites.
See `faq://graphics/faq' for PIXAR ordering info.
Hobby Animation
***************
This chapter's for those who want to make their own animation.
Animation Process
=================
[by charles king and angus]
Things don't necessarily have to happen in this order (or at all),
and there's room for plenty of feedback between them, especially in
computer animation, but here's the basic flow. Although it's an
advantage (both for the animator and the software) to integrate as many
stages as possible in the one package, and most `animation' packages do
so, in practice all packages have their relative merits and work may be
swapped from package to package to exploit their strengths, especially
in `high end' studios. This sequence assumes that the animation has
already been scripted.
*Model Design*
input
script
tool
Modeller
task
making the models to be animated
output
models
*Animation Design*
input
models, script
tool
Animation Package
task
planning and tuning sequences of motion, action, interaction,
...
output
animation script
*Production / Rendering*
input
models, animation script
tools
Renderer front-end, Renderer
task
generating images from which the animation is to be
constructed
output
images
*Post-Production*
input
images, script
tools
Editor, Compositor, Paint, Image Processing, other SFX
Packages
task
modifying, compositing, sequencing the images
output
final sequence of images
*Transfer*
input
sequence of images
tools
various media, media i/o hardware
task
transferring the frames to the desired medium
output
the product
Venues
======
[See Animation Sites, for FTP sites that carry animation.]
Conferences
-----------
[See References, for more information on these.]
SIGGRAPH (siggraph)
EG w'shop (eg)
CGI (cgs)
Computer Animation (cgs)
Graphics Interface
Events
------
Imagina
Prix Ars Electronica: International Competition for the Computer Arts.
This is a biennial event, so won't be on again until 1996. 1994
information follows.
~$42k US in prizes for animation.
General Info '94: (Peter Schoeber)
mail: ORF-Prix Ars Electronica, Europaplatz 3, A-4010 Linz,
Austria.
phone: +43 (732) 6900-267, fax: -270, telex: +21616
email: `schoeber@jk.uni-linz.ac.net'
Presentation: 22 jun 94.
Animation Info '94: (Christine Schpf) phone: +43 (732) 6900-218
Deadline: 28 feb 94.
Animation Media
***************
This chapter's about the various media an animation might end up on,
and how to get it there.
Both GWEB and 3DWEB
have information on animation
hardware and software.
Media Properties
================
Video
-----
(NTSC PAL SECAM HDTV fields composite component synch RGB analog
digital...)
To subscribe to the NewTeK Video Toaster mailing list:
`mail://toaster-request@bobsbox.rent.com//"subscribe toaster-l ()"'.
Video Formats
-------------
-format- -by- -use- -A/D- -comp...- -other-
VHS JVC home analog composite 1/2"
Video8/8mm Sony home analog ... 8mm
Betamax Sony home analog composite 1/2"
SVHS JVC prosumer analog ... 1/2"
Hi-8 Sony prosumer analog ... 8mm
ED Beta Sony prosumer? analog component ...
M (M1)? Matsu industrial? analog ... ...
U-Matic 3/4" Sony? industrial analog composite 3/4"
Betacam Sony industrial? analog component 1/2"
M2 Matsu broadcast? analog component ...
U-Matic SP Sony? broadcast? analog ... ...
Betacam SP Sony broadcast analog component ...
D-3 Matsu broadcast digital composite ...
DCT Ampex broadcast digital component compressed
D-2 Ampex master on-air digital composite uncompressed?
D-1 Sony master RGB digital component uncompressed
other formats?
other properties (image encoding techniques, sound quality, effective
number of `lines', ...)
notes: D-1 endorsed by SMPTE committee
Matsu == Matsushita == Panasonic
Film
----
(8mm super-8 16,32,72mm anamorphic stock ...)
normal film grain ~2500 lpi resolution.
slow film <-> higher resolution.
32mm: 0.875" x 1.3125" (2:3)
Media I/O
=========
(VCRs genlocks frame-stores film-scanners)
*Film Recorders:* most film recorders have at least 2000 lpi
resolution, 4000 is typical. for optimum quality, your image should be
a little over twice the resolution of the recording medium.
*Screen-To-Camera:* a cheap (but surprisingly effective) option for
images that can be displayed at full resolution on your monitor is to
photograph the screen directly using a single-framing camera. film
better than super-8 is likely to be overkill. any lights on your
monitor should be taped over, and the whole lot should be put under a
black hood (made of cardboard or anything else handy). A slow film
(100 ASA or slower, the slower the better), f8 exposure, and loong
exposures should eliminate any scanline artifacts.
Resolution / Aspect
-------------------
film recorders: 2000+ lpi (4000 typical).
35mm: ~2500 lpi at .875" x 1.3125" ~= 2200 x 3300 pixels. (2:3)
lpi == lines per inch.
Career Animation
****************
This chapter's for those who want to make a career of computer
animation.
(see Hobby Animation for Animation Process, Software, Venues)
3DWEB holds resumes, and
has information on job offers, CGI production houses, organisations,
laboratories and projects.
GWEB has industry interviews,
information on production houses, and job listings.
Your Union
==========
The Motion Picture Screen Cartoonists and Affiliated Optical
Electronic and Graphic Arts, Local 839 IATSE (California) has an ftp
site with copies of their negotiated awards, news, courses, etc:
`ftp://ftp.netcom.com/pub/mpsc839/' (email `mpsc@netcom.com' for more)
Animation Theory
****************
This chapter covers the basics of what computer animation is about
according to graphics academics (well, it's meant to).
Types of Computer Animation
===========================
2-d
---
Most computer animation takes place in the 3-d world, as our world is
itself basically 3-d, and model interpolation becomes a problem in
fewer dimensions, due to a lack of context. 2-d animation packages
mostly replicate the processes of cel-based animation, where
"key-frames" are used to plot the course of the animation, and the
"inbetweens" (interpolating the keys) are filled in later (by an
animator, not the computer). The main difference is that the images
are created using pixel-based, rather than oil-based techniques.
"Morphing" is probably the major 2-d animation technique in use today.
Like most other computer work used for SFX in film (wire-removal,
compositing, other retouching, etc), it is largely a matter of image
manipulation (image processing) rather than image creation (computer
graphics), although morphing *is* an animated technique, unlike many
other SFX `graphics' techniques. A good starter on morphing by Valerie
Hall (1992) is here
,
it references more detailed works for those interested, she's also
written a morphing article in DDJ (1993).
3-d
---
Almost all `computer animation' done today is done within the
"event-based" or, interchangeably, "track-based" computer animation
paradigm, which is based loosely on the key-framing system used in
cel-based animation. Most computer animation systems today are built
around time-varying parameters, known as "tracks", which determine the
state of the animation world at any time. Tracks take the place of the
variables which determine the state of a static scene: they're
`animation variables'. A track's value at a given time depends on the
"events" (