Game Development Reference
where CFDictionaryRef is an immutable dictionary object that allows the copying of
the object and its key value. One last consideration for this example is that as you are
now creating multiple physics simulations simultaneously, you may have to decrease
the frequency of the time steps to allow the animations to proceed smoothly. Multitouch
can become programmatically complex, but the physics are pretty simple. The event-
handling guide for your particular development language should give detailed guidance
on handling the event chain.
One of the major advantages of touch screens is that their layout and actions are entirely
software based. That is to say, if a certain button does not pertain to the current layout,
it can be discarded and the freed space used for additional relevant controls. We will
discuss other less obvious considerations in the following sections.
The flip side of the advantage of not being locked into a set of physical buttons is that
the user must rely almost entirely on vision to interact with the controls. At least one of
the authors of this topic uses a keyboard with no letters on it at all, instead relying totally
on the physical position of the keys to determine which key to strike. This would be
much harder without the tactile and audio cues to signify that the correct key has been
pressed. Indeed, it is easy to tell when he is typing poorly because the backspace key is
much louder than the rest!
The method of including physical feedback to assist a user in interaction with entirely
virtual objects is known as haptic feedback . The first use of haptic feedback in games
was limited to arcade games such as Motocross , in which the handlebars shook after an
in-game impact. It is now considered standard on video game controllers, which vibrate
to inform the user of some event.
In the realm of touch screens, haptic feedback is used to inform the user of a successful
key strike or other touch-based event. Some touch screens even incorporate some
movement of the entire screen when pressed. This feedback still doesn't allow touch
typing, as it only dynamically responds and provides no static tactile feedback for dif‐
Modeling Touch Screens in Games
Given their planar nature and the lack of inherent haptic feedback, touch screens can
be an easy way to implement controls with which a character in a game can interact.
The amount of physical modeling required to create a realistic in-game keyboard is
pretty intense. Thus, there are very few examples of an in-game character having to sit
down and type a code in to a terminal via a standard keyboard.