A billiards game with realistic physics was implemented in C++ and OpenGL. The game incorporated some user assists such as line of sight etc, complete haptics integration from the device and auditory feedback. A sample screenshot from the game is given in Figure 10. The game was tested on a laptop having 1 Gb of RAM, 128 Mb ATI graphics card and 1.6 MHz Centrino processor. The game gave a 30 Hz frame rate and around 1 kHz update rate for the haptic loop.

The HAPSTICK interface shown below was designed and constructed for the haptic simulation of the Billiards game. The device allows motion in 3 d.o.f (Two rotations: pitch and yaw, and one translation) with haptic feedback along the translation.

Experimental calibration was done on the system at many levels. The first experiment was performed by attaching a triaxial accelerometer (from PCB Piezotronics) to the tip of the cue stick attached to the device. This sensor has a resonant frequency of 25 KHz while sampling at 10 KHz. A user was then asked to play a normal follow shtot using the cue stick interface. The accelerometer data was passed through a low pass filter to eliminate jitters. The acceleration profile was then compared to the results presented by Alciatore © who recorded the data on a professional billiards player. We found that our data was analogous and comparable to the data recorded by Alciatore © .

• Swindells, C., et al. , “TorqueBAR: An ungrounded haptic feedback device”, International Conference on MultiModal interfaces, ICMI, 2003.

•  Jebara, T., et al. , “Stochsticks: Augmenting the Biiliards Experience with probabilistic visionand wearable computers”, Proc. of the Intl. Symposium on Wearable Computers, ISWC, 1997.

•  Larsen, L.B., “Development of automatic pool trainer”, Proceedings of the Fourth Danish HCI Research Symposium, HCIRN, 2004.

•  Yersin, B., “Virtual Billiards”, Student project, VRLAB, Swiss Federal Institute of Technology, 2004.