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 Features
Creating an Interactive
Audio Environment
Audio
Object Vocabulary
An audio
object vocabulary is a method by which game objects (not necessarily just
speaking ones) talk to each other and the player. The methods of communication
vary from object to object and from context to context. There are three
types of object interaction: direct, indirect, and environmental.
Direct Communication
An object communicates directly as a cause of direct action on its part.
When the ball hits the paddle in the old arcade game Pong, it makes
a bleep. This is direct object interaction. Unfortunately, most games
haven't explored far beyond this simplistic level of object interaction.
Direct communication is important when you want to convey specific audio
cues, such as a scream of pain when you shoot a monster, or the creak
of a wooden rocker when you push back a rocking chair. In Monolith Production's
Claw, I found it important that every character had something different
to say when you interact with him or her (or it), even if it's in combat.
For example, a melodramatic character, while dying, would say "I'm dying...
I'm dying... I'm dying... I'm dead," with an animation to suit. A more
primitive character would emit a squawk, and a more substantial enemy
would yell out, "I curse you, Claw" as he falls to his death. When you
hit a lounge-lizard-turned palace-guard-merman, he would say, deadpan,
"Ouch that hurt quite a bit."
As always, a variety of audio cues are paramount in ensuring that a set
of quotes doesn't become repetitive. From a programming standpoint, that
may require a bit more intelligence to pick out the quotes. A buffer with
an index to the most recently used quotes helps a lot because it shields
the player from experiencing the same "random" set of sounds in rapid
succession.
Indirect Communication
This is an indirect method of object interaction. That is, by causing
something to happen in the game, something else responds sonically. A
typical example of this is a "sighting" state for an enemy. When an enemy
sees you, and his or her AI changes, a sonic cue that signifies that change
may be appropriate. In Monolith's Blood, for example, cultists
scream in a terrifying foreign language (created for the game drama) a
series of epithets when they spot the player (Figure 2). In Claw,
every enemy has something different to say in the "sighting" state. A
female boss taunts Claw in a mildly suggestive manner when they come into
contact. A goofy bear sailor exclaims "I don't like you" when he sees
a player.
Other sonic cues may convey indirect object interaction. Your character
may begin breathing heavily when he or she is tired (health is less than
some coefficient). Your metal body suit emits a rubbing, squeaky noise
that signifies rusting. In addition to sonic cues that help convey complex
visual phenomena, certain characters within the game display behaviors
that can be conveyed easily through sonic cues, even if they aren't represented
visually. Indirect cues can be based on a number of different motivating
factors, the rules of which can be determined at the game design stage.
For example, in Blizzard's Warcraft II, clicking on an ax-throwing
troll more than once causes it to respond with annoyance, even though
no animation is being shown. This is highly effective character enhancement.
Environmental Communication
A character or object in the game may generate a system of audio cues
on its own, irrespective of its communication to the player. This is purely
a function of a character's existence in its environment. It may be busy
chatting to itself or other characters. It may generate a sound or a series
of sounds on its own. Our goofy bear sailor from Claw will comment
on how hungry he is or where his pet rat might be when he's in an idle
state (Figure 3). Depending on where he is in the game, Caleb (the character
you play in Blood) may pick from a variety of different show tunes
to sing while he's taking a break from the carnage. A thespian tiger from
Claw recites different Shakespearean passages as he muses on his
own omnipotence.
Environmental communication need not be comic, nor does it need to be
vocal. A swishing blade and a humming motor sound signifies an industrial
fan in Blood, while a phone may be ringing intermittently. A character
may pass by an alien hive, with pods emitting a terrifying whine.
Environmental communication is paramount in reinforcing a character or
object's existence in the game environment. The character literally comes
alive as a personality or physical entity. But as with all different types
of object interaction, it's important to remember to keep a consistent
set of sounds from character to character. In Claw, I made a decision
to use three different idle cues (environmental communication), four different
sighting cues (indirect communication), and between eight and nine sounds
(direct communication) to describe each character sonically. In the end,
most characters used more and some less than that average. However, planning
the audio object vocabulary ahead of time helped to maximize the use of
memory allotted to sound in the game.
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