Game Development Reference
In-Depth Information
pedals, dance mats, fishing rods, bongo drums, cameras, and microphones. If you
build a game that requires these items, you limit the size of your market to a spe-
cialist audience, and there isn't room to discuss such issues in a work on general
game design. You should design for the default control devices shipped with a
machine if at all possible. Only support extra-cost devices if using them signifi-
cantly enhances the player's experience, or if you are intentionally designing a
technology-driven game to exploit the device.
For most of their history, input devices for personal computers differed greatly from
those of game consoles, so the two were best discussed separately. Console games
never used analog joysticks; PC games never used D-pads. Now, both types of
machines can use either, so we'll look at the various input devices independently
of the platforms.
Terminology
The following discussion uses the game industry's standard terminology for the
kinds of data that control devices send to the processor as the result of player
inputs. You may find some familiar terms that nevertheless require explanation,
because the game industry uses those terms in ways that may differ from what
you're used to.
Most input devices—the mouse being a notable exception—default to a neutral
position. To send a signal to the game, the user must push, pull, grasp, or press the
device to deflect it, and a spring-loaded mechanism returns it to the neutral posi-
tion when the player releases the device. Joysticks and D-pads return to center;
buttons and keys return to the
off
state.
A device that can return only two specific signals is called a
binary device
, the sig-
nals generally being interpreted as
off
and
on
. Another common kind of input
device transmits a value from a range of many possible values and the industry, for
historical reasons, calls these
analog devices
. Any game control device can be classed
as either analog or binary, though all of the technology is digital.
Don't confuse the type of data (binary or analog) with the
dimensionality
of the
device. A one-dimensional device transmits one datum, and a two-dimensional
device transmits two data, and so on, regardless of whether they transmit binary
or analog data.
A device that returns data about its current position as measured from the neutral
position provides
absolute
values. Such a device—a joystick, for example—can
travel only a limited distance in any direction, and so it transmits values in a range
from zero to its maximum.
Other devices offer effectively unlimited travel and have no neutral position. These
return
relative
values, that is, the relative distance that the device has traveled from
its previous position. Mouse wheels and track balls are examples; the player may
rotate them indefinitely.
