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<t><tr><td align="center"><font ="er">Larger than Half-Life</font><p>
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<i>Already receiving industry accolades, Valve's <i>Half-Life 2</i>
computer game, expected to be released this month, features realistic
human character models, including scientist Gordon Freeman (above),
real-world physics, and advanced AI, all within an emotive story.</i>
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<p>
<i>Valve's highly anticipated computer game sequel pushes gaming into another realm</i></p><p>
<b>By Martin McEachern</b><br>Just as motion pictures began as a
technological novelty, interactive storytelling remains in a similar
state, awaiting classics that will finally unleash the emotional
potential of the medium. Millions of players would agree that one such
classic is <i>Half-Life</i>, a 1998 PC title from Valve that
obliterated the formulaic mold of the first-person shooter by charging
its narrative structure and action-packed gameplay with "real" emotion.
</p><p>
Now, a little more than five years later, it appears that this groundbreaking title is being followed by another?<i>Half-Life 2</i>?whose
realism, interactivity, and artificial intelligence have already earned
it industry accolades, including E3's Best of Show, months before its
mid-March release. </p>
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<p>
<i>Half-Life 2</i>'s
story line picks up where the original left off, with Gordon Freeman, a
government scientist, once again battling aliens that are pouring
through an inter-dimensional doorway that he unwittingly opened as a
result of a botched physics experiment. While the plot may seem typical
for the genre, the execution of the original, and now the sequel, by
the artists at Valve was anything but. According to Valve's founder and
managing director Gabe Newell, <i>Half-Life</i> became the new
watermark for first-person shooters because it was the first to present
a "seamless string of surprising events," a mystery that unfolded with
cinematic suspense and pacing, all within a consistently dark and
spooky atmosphere.</p><p>
Unlike similar titles in which the gameplay entails little more than
reaching a level's end or finding color-coded keys to color-coded
doors, <i>Half-Life 1</i> and <i>2</i>
are engrossing because their goals and structural high points elicit a
wider variety of emotional reactions from the player. Gordon Freeman,
far from being a trigger-happy cardboard cutout, is a multi-dimensional
character whose actions and decisions are complicated by simulated
real-life consequences and conflicting motivations, including survival
and heroic altruism. </p>
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In fact, the intensity of the player's immersion in the game is
achieved through two bold departures from current conventions in
computer-game character development, both of which radically affect the
player's point of view. First, at a time when developers are relying
more and more on elaborate cut-scenes, third-person scripted sequences,
and celebrity voice-acting talent to create fully formed characters, <i>Half-Life</i>'s
protagonist never says a word throughout the entire game. Second, the
game doesn't allow the player to experience the story through anyone's
eyes but Freeman's, so the character is never privy to any more
knowledge than the player, thus encouraging the player to empathize
with Freeman. As Newell states, "You are Gordon Freeman." </p>
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<td><font ="suber"><b>Half-Life Retooled </b></font></td>
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<p>
The sequel finds Gordon?now under the employ of the G-Man, a mysterious
briefcase-toting figure from the original?charged with saving Earth
before its resources are depleted and mankind is driven into extinction
by the aliens. His mission takes him to City 17, a fictitious European
locale resembling a hodgepodge of such Northern European towns as
Budapest, Prague, and Amsterdam, where Old World quaintness collides
with high technology and futuristic flourishes. Forging across the
sprawling cityscape and beyond, Gordon uncovers the ambiguous agendas
of those around him, discerns friend from foe, and tries to chart the
right course toward his mission's objective. </p>
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Along the way, Gordon contends with the ubiquitous combine soldiers?the
city's corrupt and heavily armored police force?as well as a rogues'
gallery of aliens, including a 50-foot-tall, flea-like creature with
impaling legs called a strider; the pack-hunting ant lions; the
water-dwelling hydra; and the parasitic headcrabs, which commandeer
human bodies by affixing themselves to a victim's skull. </p>
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<i>The
game features an array of characters, including the corrupt combine
soldiers (above) and a host of unusual alien creatures such as the
50-foot-tall strider, all created using Softimage|XSI. </i>
<br>
<p>
According to Newell, <i>Half-Life 2</i>
was designed from the outset to fulfill the original game's potential
as a medium for first-person storytelling. The sequel, therefore,
abstains from using cutaways and cinematics that disrupt the player's
subjective point of view (POV) on the narrative. In addition, the
player's immersion in the first-person POV is intensified through an
array of technological advancements debuting in <i>Half-Life 2</i>.
The majority of those are embodied in the title's new game engine,
dubbed Source. While the original release was powered by Quake
technology from id Software, Valve spent the past four years
collaborating with Havok, developers of the Havok physics engine, to
deliver enhanced character physics and environmental dynamics, which
allow for unprecedented interactivity with objects adhering to the laws
of nature. </p>
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<i>Half-Life 2</i>
also marks the arrival of Softimage as a major contender vying for
game-authoring software supremacy. Throwing down the gauntlet to
Discreet (3ds max) and Alias Systems (Maya), Softimage worked closely
with Valve, making Softimage|XSI the sole digital content creation
software used to create the game, and, thereby, resulting in an
impressive showcase for its real-time 3D content creation capabilities.
</p>
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<td><font ="suber"><b>Level Playing Field</b></font></td>
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<p>
<i>Half-Life 2</i>'s
environments, which are spread over 10 chapters, range from small
indoor areas to the war-torn City 17, a massive urban dystopia where
streets are lined with burnt-out buildings, and fires smol-der beneath
leaden skies. Valve's unique, multi-pronged pipeline for building the
levels began with the formation of a "cabal," a team of modelers, level
designers, and programmers who were responsible for the design and
gameplay of a particular level. </p>
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<i>The
game's dark, foreboding atmosphere resulted from the use of various CG
light sources. This ominous look was further enhanced with volumetric
fog and effects primitives, such as smoke and fire. </i>
<br>
<p>
In the first branch of the pipeline, the cabal's level designers built
low-resolution texture maps for the environment and then replaced them
with plain "orange" textures that accelerated play-testing and
experimentation, saving the cabal from painting detailed textures for
scenery that would likely undergo substantial changes later. In the
second branch of the pipeline, the programmers worked on the code for
the support "entities" in the level, such as monsters, vehicles,
turrets, and gates. And in the final branch, the modelers built light,
"placeholder" geometry for the various entities. Finally, once there
was enough content to "play," the three branches converged and the
cabal members commenced testing their levels using the placeholder
models, orange textures, and temporary code. </p>
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<p>
During this iterative process, every idea is discussed within the
cabal, and interesting ones are tried, to see if they add to the
gameplay experience. Any of these experiments has the potential to
radically alter the scenery or entities in a level, but with Valve's
cabal-based pipeline, each level can be previsualized and play-tested
with the least possible effort expended on creating detailed content
that ultimately will be changed or deleted. "By separating the art and
gameplay branches of production, we were able to avoid a potentially
huge amount of wasted time and effort on the art side by using
placeholders instead of real art," says senior engineer Rick Ellis. </p>
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The developer further streamlined its pipeline by decoupling the art
asset and level design streams of production as well. All the art
assets were prefabricated in XSI by a team of artists and placed in a
huge "backlot" of props for all the cabals to use. Designed to be
easily editable through a cut-and-paste style, much of this virtual
backlot will be made available to mod authors. It also will house every
texture map and model used in the game, including such ready-made
pieces of scenery as power stations, airplane hangars, and brick
buildings, complete with a lower floor, a roof, and an expandable
mid-section. It also will contain similar information for generic
items, such as barrels, desks, chairs, tables, debris, and vehicles. </p>
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<i><i>Half-Life 2</i>'s level designers used the new Hammer world construction tool to place objects, edit the terrain, and control the AI.</i>
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Valve's world-creation Hammer tool set also features a proprietary
materials system that endows these objects with the physical properties
of their applied textures, including weight, density, and sound. For
example, applying a brick texture to a rectangular object will
automatically make it behave like a brick of that exact size; it will
sink if dropped in water, explode if shot, and so forth. Objects also
will acquire the friction and collision properties of their textures.
Therefore, if a chair is mapped with a wood texture, it will not only
float like wood and sound like wood, but, if scraped against a wall,
also splinter like wood. </p>
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<p>
After the levels were play-tested and textured, the group lit them with
lightmaps, whereby each surface's texture was paired with maps of
various lighting conditions for that surface. For illuminating the
props, the artists used vertex lighting to store the lighting
information at the model's vertex. Depending on the demands of each
scene, they drew upon a wide variety of lights, including spots,
directionals, points, and ambients, to maintain the game's ominous
lighting and tone. </p>
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<p>
The dark, foreboding atmosphere overhanging the entire adventure also
was enhanced with volumetric fog, one of Source's numerous effects
"primitives," which also include fire and smoke. "On top of all this,
Source's shaders allowed us to make virtually any effect we could dream
of," says Ellis, noting that no off-the-shelf tools or plug-ins were
used for the special effects. </p>
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<td><font ="suber"><b>Formidable AI</b></font></td>
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<p>
One of the pivotal sequences in the game unfolds on a dried-up
seafloor, where Freeman tangles with soldiers and ant lions, and speeds
across a sandy gorge in a land buggy to elude an aerial assault by
alien hovercraft, his only shelter provided by the rocky terrain, some
overturned cars, and a half-sunken skeleton of a submarine. While the
level displays Hammer's power in creating dynamic natural environments,
it is more impressive for its demonstration of <i>Half-Life 2</i>'s advancements in contextual AI programming.
</p>
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<p>
If Freeman tries to hide behind a rock, a car, or a closed door in the
submarine, the AI programming provides the aliens and the soldiers with
numerous paths to choose from in order to find him, such as pushing the
car over the edge of the gorge, knocking out windows in the sub and
peering through them, punching or shooting through the door, or
climbing the struts and beams of the sub to continue the pursuit. These
are not scripted sequences, but rather the AI working its way through
the level, checking to see if the player is nearby, searching
relentlessly for new ways to launch an attack, and then encountering
and solving all the obstacles in its way until the target is destroyed.
In a sequence set in City 17, for example, Freeman's attempt to elude
the 50-foot-tall strider by bolting under an overpass is thwarted when
the creature, through its AI programming, "learns" to get past the
bridge by crouching down and clambering underneath it. </p>
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<p>
Maximizing the performance of this highly advanced AI system meant the
artists had to refrain from overpopulating the levels with AI entities.
Conversely, inserting too few entities would have resulted in an empty
and uninteresting level. </p>
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<p>
Achieving optimal AI during gameplay by adjusting the number of
entities in a level also was crucial to the performance of the
brand-new physics engine developed for the game. The new engine not
only melds the gameplay with unprecedented environmental interactivity
and newfound realism in complex physics interactions, but, for the
first time, also makes all the environmental objects available to the
player for solving puzzles, avoiding enemy fire, or even using as
weaponry for combat. "The new physics system allowed us to create
interesting puzzle and gameplay experiences that were not possible with
the Quake-based engine," says Ellis. </p>
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<td><font ="suber"><b>Character Building</b></font></td>
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<p>
Valve's bar-raising mandate for the game's graphics and gameplay also
extended to the modeling, texturing, and animation of the characters.
From their detailed brows, to the radial bands in their irises, to the
imperceptible furrows in their foreheads, Gordon Freeman and the rest
of the main cast are the result of an aggressive mission to leapfrog
the current state of the art in character creation. </p>
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<p>
All the characters, including the humans and the more geometrically
complex creatures, such as the gargantuan strider, were surfaced using
XSI's subdivision surface tools, which, says Ellis, provided not only a
highly refined interface for intuitive, organic modeling, but also the
expedience of automatically converting the finished subdivision surface
models to their component triangles for in-game use. </p>
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<p>
For modeling each character, the team used photographic references of
actual people, importing orthographic and perspective photos overlaid
with grid markings into the XSI viewports to guide the modeling
process. In addition, a second set of photos, comprising front and side
images of the same people, were shot in more diffuse lighting for
creating the face textures. The front and side textures, once resized,
merged, and retouched in Adobe's Photoshop, were mapped to the models
in XSI at a resolution of 2000x1500. The characters' eyes also were
modeled elliptically, outfitted with a series of constraints, and
placed off-center. Consequently, when facing the screen, the characters
stare directly at the player without displaying the cross-eyed look
that plagues most game characters. </p>
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<p>
Next, to ensure that the sequel would be completely devoid of the
generic models that were used in the original game to furnish, for
instance, the Black Mesa lab with a large staff of scientists, Valve
developed a morphing technology that blends a core set of models for
the game's common roles in almost infinite ways to render them entirely
distinct from one another. Using the same morph targets sculpted for
facial animation, the system automatically alters the facial geometry
to create, for example, a flatter or broader nose, or a squarer jaw. As
a result, all the scientists, soldiers, and other homogeneous
characters appear as unique, differen-tiated models. Nevertheless,
because the overall personality of a character's face is forged
primarily by the facial texture, the system also draws upon a large
database of facial texture maps to diversify and individualize the
digital citizenry of City 17. </p>
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<i>Valve's
powerful facial animation system uses 40 different muscles to control
nearly every nuance of a character's expression, with the eyes, lips,
and brows exhibiting the highest level of expressivity.</i>
<br>
<p>
For the characters' bodies, the alien creatures required custom IK
rigs, while all the main human characters were bound to a single,
scalable base skeleton that was easily modified to suit each
character's proportions. Both the humanoid default rig and the custom
alien rigs were constructed in multiple levels of joint detail,
providing the appropriate degree of articulation for the corresponding
levels of detail (LOD) created for all the characters. Artists used
most of these LODs to regulate the geometric complexity of a character
with the proximity of the camera. However, one low-polygon version and
its respective low-bone rig was used to create collision models
showcasing the breakthrough rag-doll effects of the Havok 2 physics
engine that simulate the involuntary behavior of the human body when
acted upon by external forces, such as gravity, inertia, or concussive
blows. </p>
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<td><font ="suber"><b>After Half-Life</b></font></td>
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<p>
In addition to more sophisticated AI, real-world physics, new
technology for facial expressions, body language, and lip-synching, <i>Half-Life 2</i>'s
Source engine features drivable vehicles and a terrain generator. It
also sports advanced displacement mapping technology?another boon for
mod makers?which enables dynamic, fluid scenery elements such as water,
sand, or snow to deform in real time. </p>
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<i>The artists gave the characters, including Alyx, Freeman's sidekick throughout the game, a wide range of facial expressions.</i>
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<p>
Unfortunately, the engine is so revolutionary that Valve has already
fallen victim to a major code theft by hackers eager to acquire the
technology. While forcing Valve to delay the game's initial October
2003 release date until mid-March, the theft and continued assault by
hackers are telltale signs that fans are bursting with anticipation for
the sequel, not to mention a testament to the powerful hold the
distinctive <i>Half-Life</i> narrative style has exerted over game players.
</p>
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<p>
In attempting to trace the source of this power, <i>Half-Life</i>
writer Marc Laidlaw points to the game's distinctive narrative
structure, and its ability to transfer the same drama experienced by a
passive observer into a medium where the audience is an active
participant in the story. "Games require a new way of looking at the
concept of a 'dramatic moment,' because the meaning of drama is
different for a passive observer than it is for an active participant,"
he says. "Structure is not something the actors in a story are usually
aware of. That awareness is traditionally reserved for the audience.
But for an actor in a game (the player), the moments when you perceive
structure and realize that you're playing a significant part in
assembling some larger pattern can be very compelling." </p>
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<p>
In fact, the narrative structure in the <i>Half-Life</i>
games is there to support this experience, Laidlaw notes, and to
provide opportunities for surprise and revelation that feel inevitable
rather than random. "Ideally, when you are most involved in playing <i>Half-Life 2</i>,
whether you're part of a scene with other actors, solving a puzzle, or
fighting enemies, you not only feel challenged and fully engaged, you
feel that it all means something," he says. Mastering the dichotomy of
simultaneously participating in and perceiving the story structure may,
therefore, be the key to unlocking untapped levels of emotional
involvement in computer-game storytelling. And if Laidlaw and his
teammates at Valve can achieve that goal with <i>Half-Life 2</i>, their pioneering efforts could put them on the cusp of the next era of gaming.
</p>
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<p>
<i><b>Martin McEachern</b>, a contributing editor for </i>Computer Graphics World<i>, can be reached at martin@globility.com.</i>
</p>
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<td><font ="suber"><b>Toolbox</b></font></td>
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<p>
Adobe www.adobe.com<br>Havoc www.havoc.com<br>id Software www.idsoftware.com<br>Softimage www.softimage.com</p><hr>
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<td><font ="suber"><b>High Expectations</b></font></td>
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<p>
Garnering more than 50 Game of the Year awards, the first <i>Half-Life</i>
spawned a number of successful expansions and, with the subsequent
release of the game's basic programming code, yielded a flood of
user-created modifications resulting in new, free downloadable levels
and characters. These, in turn, have led to "total conversions,"
entirely new games freely distributed over the Internet (such as <i>Counter-Strike</i>)
that have formed the basis for a massive online gaming community that
is continually weaving new threads into the ever-expanding fabric of
the <i>Half-Life</i> mythos. Consequently, during the last five years,
fan enthusiasm and the boundless creativity of the mod community have
stoked anticipation for a sequel to such a fever pitch that, upon its
release this month, <i>Half-Life 2</i> is expected to single-handedly spark a revival of the PC game industry.</p><hr>
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<td><font ="suber"><b>Mod Ware</b></font></td>
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<p>
To firmly entrench itself in the future of game development, Softimage
will package XSI EXP, a lite version of XSI, with every PC copy of <i>Half-Life 2</i>.
With this, Softimage joins Discreet (which offers gmax, a free,
scaled-down version of 3ds max) in adopting the increasingly popular
strategy of cultivating a user base from the massive mod communities
forming around blockbuster PC games. (Valve will still provide
exporters for both max and Maya, but contends that XSI EXP?which allows
modders to build models of similar complexity to those in the game?will
yield the best results.) </p>
</td>
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<tr>
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<p>
Rolled into the mod SDK will be XSI EXP, the programming code for the
AI and client systems, and nearly all the other tools developed for the
new Source engine, including the Hammer world construction tool, which
will allow modders to place objects and characters they've created in
XSI in a world, edit the terrain, add water, provide pathing
information for various AI entities, and control the AI through a
system of inputs and outputs, just as Valve's level designers did. This
move reflects Valve's continued commitment to the mod community, which
has been responsible for much of <i>Half-Life</i>'s staying power and commercial success over the past five years.</p><hr>
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<td><font ="suber"><b>Digital Actors Studio</b></font></td>
</tr>
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<p>
Surprised by how endeared they had become to some of the characters
after finishing the original game, Valve's founder, Gabe Newell, and
his fellow designers were determined to make <i>Half-Life 2</i>
a more emotional experience, to give the cast full personalities, and
to force the player to identify and empathize with many of them. </p>
</td>
</tr>
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<p>
Heightening the game's emotional involvement was the impetus for the
development of a highly sophisticated, proprietary face-acting
technology based, in part, on the facial expression studies of Paul
Ekman, a psychiatrist from the University of California, San Francisco.
Ekman's systematized facial lexicon comprises 40 keyframes of
expression, of which Valve selected 25 that could be blended into
enough hybrid expressions to serve as the basis for a new facial
animation system capable of endowing the characters with more natural
speech and greater emotional expressivity. </p>
</td>
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<tr>
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<p>
To create these keyframes of expression, the team modeled 34 blend
shapes for each character in XSI, and controlled them with an internal
proprietary tool called Faceposer, which also offers precise control
over lip synchronization. These targets were modeled below the level of
actual expressions, depicting, instead, individual facial muscles in
their flexed state, enabling the artists to create more natural facial
animation. That's because each muscle group is accessed independently,
so all the muscle movements don't occur with the same envelope and
"hit" at the same time. </p>
</td>
</tr>
<tr>
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<p>
In real time, the Source engine can combine the 34 blend shapes
non-linearly to make the characters smile, sneer, snarl, or look
fearful, menacing, sinister, victorious, condescending, and so forth.
It also automatically lip-syncs the dialogue in any one of numerous
languages, extracting phonemes from a .wav file and forming the
corresponding phoneme blend shape for the mouth. In addition, the
engine allows the characters to shift between expressions independently
of the context of the line. The result is a finely calibrated and
unique performance for every exchange between the player and a
character. </p>
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<tr>
<td><i>Computer Graphics World</i> March, 2004</td></tr></t>
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