What is Virtual Reality?
Virtual reality (VR) refers to a world that appears to be real and has many of the properties of an actual world. As a term, virtual reality describes a system that allows one or more people to move about and react in a computer-simulated environment. In this environment, virtual objects are manipulated using various types of devices as though they were real objects. This simulated world gives a feeling of being immersed in the real world, such as the inside and outside of a product or building; the simulation includes sound and touch.
A walk-through can be characterized as a camera in a computer program that creates a first-person view of walking through a building, around a product or building, or through a landscape. A fly-through is similar to a walk-through, but the first-person camera view is like a helicopter flying through the area.
Fly-through is generally not used to describe a tour through a building. Walk-through or fly-through is the effect of a computer-generated movie. The computer images represent the real architecture or the VR presentation in which the computer images turn or move as you turn your head in the desired direction. Realistic renderings, animations, and VR are excellent tools to show the client how the building will look inside and out or how a product will operate. Design ideas can be created and easily changed at this stage.
VR requires special interface devices that transmit the simulated world’s sights, sounds, and sensations. In return, these devices record speech and movement and transmit them back to the simulation software program. Virtual reality technology is a logical step in the design process.
A VR system provides the capability of interacting with a model of any size, from molecular to astronomical. Surgeons can learn from virtual patients and practice real operations on a virtual body constructed from scanned images of the human patient. Home designers can walk around inside a house, stretching, moving, and copying shapes to create a finished product.
Buildings can be designed and placed on virtual building sites. Clients can take walk-through tours of a building before it is built and make changes as they walk through. Scientists can conduct experiments on a molecular level by placing themselves inside a model of chemical compounds. Using telerobotics, a person can see through the eyes of a robot while in a safe virtual environment in order to guide a robot into a hazardous situation.
Passive VR
Through-the-window VR, also referred to as passive VR, is a common basic VR application. Passive VR is the manipulation of a 3-D model with input from a mouse, trackball, or 3-D motion control device. This allows more than one person to see and experience the 3-D world. A variation on this is a flat-panel display with handles for movement. The window VR unit in Figure is designed to allow natural interaction with the virtual environment. Museum and showroom visitors can walk up, grab the handles, and instantly begin interacting. Observers can follow the action by moving beside the primary user. A variety of handle-mounted buttons imitate keyboard keystrokes, joystick buttons, or 3-D motion control device buttons.
Another type of through-the-window VR consists of a special stereoscopic monitor and sensing devices. The viewer wears lightweight, passive, polarized eyewear. The monitor sends the images directly to the screen to generate 3-D images by users wearing the special glasses. This technology also allows several persons to view the same image on the screen.
Head Mounted Display (HMD)
To interact visually with the simulated world, you wear a head-mounted display (HMD), which directs computer images at each eye (see Figure). The HMD tracks your head movements, including the direction in which you are looking. Using this movement information, the HMD receives updated images from the computer system, which is continually recalculating the virtual world based on your head motions. The computer generates new views quickly, preventing the view from appearing halting and jerky and lagging behind your movements. The HMD can also deliver sounds to your earphones. The tracking feature of the HMD also can be used to update the audio signal to simulate surround sound effects. The three most important HMD attributes are
- field of view (FOV)
- resolution
- weight
Field of View (FOV)
Field of View (FOV) The human visual field is approximately 2008 wide for both eyes, about 1508 for each eye, and 908 vertically. The portion of the visual field that is visible to both eyes is called the binocular overlap and is about 1008. The greater binocular overlap allows a stronger sense of depth. The necessary vertical field of view depends on the application. For example, driving simulators typically require only a narrow vertical field of view because the out-of-window view in most cars is limited in the vertical direction. In addition, scientific research into motion and balance often requires taller vertical fields of view so that test subjects can see below and above them.
Resolution
Resolution Higher resolution throughout the visual field brings out fine detail in a scene (such as the ability to read text on a car’s dashboard), makes images look more realistic, and increases the amount of information that can be displayed. The characteristics of a computer monitor are often specified as a size measure (such as 21 in.) and as input resolution (such as 1920 3 1200 pixels). Input resolution is useful in determining compatibility with a particular image generator, and pixel density is at least as important in determining visual quality. A reasonable estimate of the visual sharpness for a person with 20/20 vision is 60 pixels/degree. This means that to match human visual quality, an HMD with a field of view of 408 3 308 (H 3 V) would need to present 2400 3 1800 pixels.
Weight
A lightweight and balanced HMD helps users feel comfortable and allows for greater freedom of movement. Professional HMDs can be as light as 350 g (12 oz) or as heavy as 2 kg (4.5 lbs). A way to assist HMD weight is to install a boom mechanism that suspends the HMD from the top, although this typically restricts movement and makes the system more cumbersome. There is a dramatic range in the weights of offered HMDs.
Binocular Omni-Orientation Monitor (BOOM)
The Binocular Omni-Orientation Monitor (BOOM), developed by Fake Space, Inc., is a head-coupled stereoscopic display device (see Figure). The display is attached to a counterbalanced multilink arm system. The person can guide the counterbalanced display while looking into it like binoculars. The system is guided with tracking attached to the counterbalanced arms.
Cave Automatic Virtual Environment (CAVE)
The Cave Automatic Virtual Environment (CAVE) projects stereo images on the walls and floor of a room. CAVE was developed at the University of Illinois at Chicago to allow users to wear lightweight stereo glasses and to walk around freely inside the virtual environment. Several persons can participate within the CAVE environment as the tracking system follows the lead viewer’s position and movements, as shown in Figure.
Haptic Interface
The sense of touch is the most challenging physical sensation to simulate in a virtual world. A haptic interface is a device that relays the sense of touch and other physical sensations. In this environment, your hand and finger movements can be tracked, allowing you to reach into the virtual world and handle objects. Haptic interfaces of this type hold great potential for design engineers, allowing various team members to manipulate a product design in a virtual environment in a natural way. Although you can handle an object, it is difficult to generate sensations associated with the human touch, for example. These sensations are felt when a person touches a soft surface, picks up a heavy object or runs a finger across a bumpy surface. Very accurate and fast computer-controlled motors generate force by pushing against the user to simulate these sensations.
Haptic devices are synchronized with HMD sight and sound, and the motors must be small enough to be worn without interfering with natural movement. A simple haptic device is the desktop stylus shown in Figure. This device can apply a small force, through a mechanical linkage, to a stylus held in the user’s hand. When the stylus encounters a virtual object, the user is provided feedback that simulates the interaction. In addition, if the stylus is dragged across a textured surface, it responds with the proper vibration.
In the future, engineers may use VR to increase productivity in various areas, including virtual mock-up, assembly, and design reviews. These applications may include the realistic simulation of human factors, such as snap-fits, key component functions, and the experience of virtual forms. Virtual assemblies may include fit evaluation, maintenance path planning, manufacturability analysis, and assembly training.
Web-Enabled Virtual Reality Modeling Language (VRML)
An emerging area in the world of virtual reality is Web-enabled virtual reality modeling language (VRML). VRML is a formatting language that is used to publish virtual 3-D settings called worlds on the World Wide Web (www). Once the developer has placed the world on the Internet, the user can view it using a Web-browser plug-in. This plug-in contains controls that allow the user to move around in the virtual world as the user would like to experience it. Currently, VRML is a standard authoring language that provides authoring tools for the creation of 3-D worlds with integrated hyperlinks. The current version of VRML is viewed using a basic computer monitor and, therefore, is not fully immersive. However, the future of VRML should incorporate the use of HMDs and haptic devices, making for more truly immersive environments.
In the future, engineers may use VR to increase productivity in various areas, including virtual mock-up, assembly, and design reviews. These applications may include the realistic simulation of human factors, such as snap-fits, key component functions, and the experience of virtual forms. Virtual assemblies may include fit evaluation, maintenance path planning, manufacturability analysis, and assembly training.
VR Opportunities
A field of opportunity is available in the creation of virtual worlds. These worlds are detailed 3-D models of a wide variety of subjects. Virtual worlds need to be constructed for many different applications. Persons who can construct realistic 3-D models can be in great demand. The fields of VR geographic information systems (GIS) are combined to create intelligent worlds from which data can be obtained while occupying the virtual world. In the future, many cities will have virtual models on their Web sites.
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