In the preceding chapter, we looked at some simple interaction techniques, that included ray picking (via touch interaction), sensor interaction, or camera to target proximity. There are a large number of other interaction techniques that can be used in Augmented Reality.
One standard technique that we will also find on other mobile user interfaces, is a virtual control pad. As a mobile phone limits access to additional control devices, such as a joypad or joystick, you can emulate their behavior via a touch interface. With this technique, you can display a virtual controller on your screen and analyze the touch in this area as being equivalent to controlling a control pad. It's easy to implement and enhance the basic ray-casting technique. Control pads are generally displayed near the border of the screen, adapting to the form factor and grasping the gesture you make when you hold the device, so you can hold the device with your hand and naturally move your...