**4. The history of hardware components for VR application development**

Hardware components for VR have evolved since the inception of VR. Hardware components for VR application development are computer workstation, sensory displays, process acceleration cards, tracking system and input devices. Other specialized types of hardware that have been developed or used for VR applications are navigation devices, interaction devices and tactile and force feedback among others (Isdale, 1998; Perry, Smith, & Yang, 2004).

#### **4.1 Computer workstation**

Computer workstation is used to control several sensory display devices to immerse you in 3D virtual environment (Onyesolu & Eze, 2011). A computer workstation is a microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used to refer to a

A Survey of Some Virtual Reality Tools and Resources 27

Small CRT head mounted display uses two CRTs that are positioned on the side of the HMD. Mirrors are used to direct the scene to the viewers' eye. Unlike the projected HMD where the phosphor is illuminated by fiber optic cables, here the phosphor is illuminated by an electron gun as usual (Lane, 1993). CRT head mounted display is in many ways similar to the projected HMD. This type of HMD is heavier than most other types because of added electronic components (which also generate large amounts of heat). The user wearing this type of HMD may feel discomfort due to the heat and the weight of the HMD (Bolas, 1994). Single Column LED head mounted display uses one column of 280 LEDs. A mirror rapidly oscillates opposite from the LEDs, reflecting the image to the user's eye. The LEDs are updated 720 times per oscillation of the mirror. As the LED column updates for each column of the virtual screen, the mirror redirects the light to the viewers' eye, one column at a time, to form the image of the entire virtual screen (Aukstakalnis & Blatner, 1992). Single Column LED HMDs allow the user to interact with a virtual world and the real world simultaneously. This type of display can be used to create a virtual screen that seems to float in the real world.

One of the common problems of HMDs is that the cable connecting the HMD and a computer restricts the mobility of the user. The user can only move as far as the cable allows. If the cable is not properly managed, the user could trip over it or become entangled in it. In addition, switching frequently between a virtual world and the real world is tedious

The BOOM is mounted on a jointed mechanical arm with tracking sensors located at the joints. A counterbalance is used to stabilize the monitor, so that when the user releases the monitor, it remains in place. To view the virtual environment, the user must take hold of the monitor and put her face up to it. The computer will generate an appropriate scene based on the position

Some of the problems associated with HMDs can be solved by using a BOOM display. The user does not have to wear a BOOM display as in the case of an HMD. This means that crossing the boundary between a virtual world and the real world is simply a matter of

and orientation of the joints on the mechanical arm (Aukstakalnis & Blatner, 1992).

Fig. 1. Visette 45 SXGA head mounted display (HMD)

**4.2.2 Binocular Omni-Orientation Monitor (BOOM)** 

moving your eyes away from the BOOM.

and tiresome.

mainframe computer terminal or a personal computer (PC) connected to a network. Workstations had offered higher performance than personal computers, especially with respect to CPU and graphics, memory capacity and multitasking capability. They are optimized for the visualization and manipulation of different types of complex data such as 3D mechanical design, engineering simulation animation and rendering of images, and mathematical plots. Workstations are the first segment of the computer market to present advanced accessories and collaboration tools. Presently, the workstation market is highly commoditized and is dominated by large PC vendors, such as Dell and HP, selling Microsoft Windows/Linux running on Intel Xeon/AMD Opteron. Alternative UNIX based platforms are provided by Apple Inc., Sun Microsystems, and Silicon Graphics International (SGI) (http://en.wikipedia.org/wiki/Workstation).

## **4.2 Sensory displays**

Sensory displays are used to display the simulated virtual worlds to the user. The most common sensory displays are the computer visual display unit, the head-mounted display (HMD) for 3D visual and headphones for 3D audio.
