Game Development Reference
In-Depth Information
User Interface
The concept of a
user interface
should be familiar to you from computer software
generally, but in a game the user interface has a more complex role. Most computer
programs are tools of some kind: word-processing tools, web-browsing tools, paint-
ing tools, and so on. They are designed to be as efficient as possible and to present
the user's work clearly. Games are different because the player's actions are
not
sup-
posed to be as efficient as possible; they are obstructed by the challenges of the
game. Most games also hide information from the player, revealing it only as the
player advances. A game's user interface is supposed to entertain as well as to
facilitate.
The user interface mediates between the core mechanics of the game and the player
(see
Figure 2.1
). It takes the challenges that are generated by the core mechanics
(driving a racing car, for example) and turns them into graphics on the screen and
sound from the speakers. It also turns the player's button presses and movements
on the keyboard or controller into actions within the context of the game. If it does
this smoothly and naturally, the player comes to associate the button press with
the action. She no longer has to think, “I must press button A to apply the brakes.”
Instead she thinks, “Brakes!” and presses button A automatically. The user interface
interprets the button press as the braking action and informs the core mechanics;
the core mechanics determine the effect of the braking and send an instruction
back to the user interface telling it to show the result. The user interface adjusts the
animation to show the car slowing down and presents it to the player. All this hap-
pens in a fraction of a second.
FIGURE 2.1
The relationships
among the core
mechanics, the user
interface, and the
player
Inputs
Actions
USER
INTERFACE
CORE
MECHANICS
PLAYER
Outputs
Challenges
Because the user interface lies between the player and the core mechanics, it is
sometimes referred to as the
presentation layer.
The user interface does more than display the outputs and receive the inputs. It
also presents the story of the game, if there is any, and creates the sensory embodi-
ment of the game world—all the images and sounds of the world and, if the game
machine has a vibrating controller, the vibrations of the world, too. All the artwork
and all the audio of the game are part of its user interface, its presentation layer.
Two essential feat ures of the user interface of a game are its
camera model
and its
interaction model
, as shown in
Figure 2.2
.
