Context

Interaction of users with virtual worlds in computer games is usually done through the available hardware devices, which in most cases are mouse, keyboard, or a joystick. In some cases the joystick can be an advanced version, providing additional control elements such as steering wheel or application-dependent controls. These devices translate actions by the user from the real world into actions and events in the virtual world.

One of our interests is to extend the capabilities with which a game player can interact with the virtual game world, employing the ways in which the user would interact with his/her real environment. This requires to employ additional sensors and link them to natural interaction paradigms.

Tilt Sensing

We have connected tilt sensors to a laptop computer, using the USB port for power and data transfer. The tilt data which are continuously reveived, are processed using Virtools^TM, which provides the platform for physical interaction with virtual devices. As an example implementation, we have written a board game in which the user has to balance a rolling ball along a labyrinth. The sole interaction to move the ball is through tilting the laptop, which results in virtual gravity forces which act on the ball.

Blowing into Virtual Space

A very direct interaction is to blow onto a virtual object and make it move through the air flow pressure. We have developed a prototype of such an interaction, allowing the user to blow towards the computer screen. Users who experience this interaction for the first time, are always surprised and puzzled when they see the virtual object moving as a consequence of their breath blow onto the screen.

The technical implementation of this interaction does not measure the actual air pressure, but senses a secondary side effect of the user's blowing action: the sound which is created when someone blows onto a microphone. We assume that the sound level is approximately proportional to the speed and intensity of the air flow. The built-in microphone in our demonstration laptop pics up this sound, and the signal is processed using Virtools^TM. From here, the "force" from the blowing can be applied to any virtual object, either moving it away, or changing its behavior (e.g. a virtual flame).

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