Physics for Game Developers, 2nd Edition

Chapter 20. Touch Screens

It is hard to deny that we are currently moving toward a post-PC computing environment. The proliferation of smartphones, tablets, and other mobile computing platforms will have far-reaching implications for how people interact with computers. These form factors do not allow for the more traditional mouse and keyboard of input for games and therefore rely heavily on the use of touch screens. This chapter aims to give you some background on the different types of touch screens, how they work, and their technical limitations. Note that we will extend our particle simulator to work with the iPhone’s capacitive touch screen; the final product is very similar to the mouse-driven version but provides a starting point for a touch-driven physics simulator.

While this chapter will primarily deal with the most two most common types of touch-sensitive screens, resistive and capacitive, the following section gives an overview of many different types. In the future we may see a move to more exotic devices, especially for large-format computing devices.

Types of Touch Screens

Resistive

Resistive touch screens are basically a giant network of tiny buttons. Some of them have 4,096 × 4,096 buttons in a single square inch! OK, so they are not quite just normal buttons, but they come close. Resistive touch screens have at least two layers of conductors with an air gap between them. As you press on the screen, you close the gap. Bam, circuit complete, button pressed. We will flesh ...