Virtual Reality (VR) Kyle Maitland Department of Computer Science University of Wisconsin Platteville



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Virtual Reality (VR)
Kyle Maitland

Department of Computer Science

University of Wisconsin Platteville

Platteville WI, 53818

maitlandk@uwplatt.edu


Abstract
The current level of virtual reality systems is not as advanced as it is portrayed by movies. However, virtual reality systems are more widely used than thought. A VR system is simply a three-dimensional image or environment that can be interacted with, whether it is a simple 3D game or an interactive simulator. VR systems can be described by their system type, hardware, and hardware level. Their systems’ type describes the kind of environment; the hardware is how the VR is interacted with by a user stand-point; its hardware level describes the degree to which the hardware is implemented. VR systems can be a useful tool in a learning environment, for example a VR system was used in the teaching and training of med school students to practice a simple surgery routine with a head-mounted simulator.


Introduction
This paper will identify and explain the different types of 3 categories that make a VR-System (system type, hardware, hardware levels). A good, yet simple definition of a VR is any computer generated simulation of a three-dimensional image or environment that can be interacted in a seemingly real or physical way by a person or computer.

System Types
Window on world systems (WoW) uses the monitor to display the visual environment, and is sometimes referred to as Desktop VR. The main challenge to windows on worlds is making the environment look real, sound real and have the objects act real.

Video mapping is a variation of the windows on worlds system. It merges the video input of the user with 2D computer graphics. The user will watch a monitor that will show their body’s interaction with the VR environment. A good example would be the early Kinect for the Xbox 360. It simply mirrored your body movements on the screen with a motion sensor for video input.

The immersive system completely immerses the user’s personal sight within the virtual environment. The simplest way to utilize the immersive system is with the use of a head mounted display, such as a helmet or face mask that can be free ranging, tethered, or even attached to some stand. The HUD will have a form of a visual and audio display so as to bring out the full effect of the VR system. A nice immersive system set up is called the “cave”, which consists of multiple large projecting displays set up around a room so as to create the VR environment. (Fig. 1)vr cave.jpg


Telepresence is a visualizing complete computer generated world. The world is created using remote sensors in the real world on a form of a human operator and/or robot, and even in some cases, on the ends of a tool. This kind of VR system is used a lot of times in the movie world when animating CG environments around actors on a green screen. This type of VR system is useful with surgeons using small instruments on cables to perform detailed surgeries without cutting too major of a hole in a patient. With the use of telepresence on robots, deep sea and volcanic exploration can be achieved much easier and safer by simply sending in the robot with a camera attached.

Mixed reality is a form of mixing telepresence and other VR systems, such as immersive systems. Using the generated input of the telepresence system, mixed reality systems will generate a VR environment in which a user can then interact with. A good example of this would be a fighter pilot using previously record flights to test a new jet’s capabilities in a VR environment.

Hardware
Image generators
The most time consuming task of any VR system is the creation of the 3D environment. A computer with faster graphic generating is ideal when working with VR systems. Because of this, image generating cards, most of which are based on the Intel i860 processor, is the first item to be taken into effect when working on a set budget. Image generating cards can cost up to 10,000$, and on much more advance VR systems can even end up costing around $100,000.

Position tracking
Ultrasonic sensors can be used to track position and orientation. A set of emitters are pulsed in sequence and the time lag to the receiver is then measured. Once data is collected, triangulation allows us to calculate positions. A problem with ultrasonic sensors is interference from echoes or other devices, which can lead to un-accurate data collection resulting in poor 3D environment creation.

Magnetic trackers use sets of coils to pulse magnetic fields, which allow magnetic sensors to determine the strength and angle of the pulse fields. The drawback to magnetic tracking is possible interference with ferrous materials in the fields, the range limits on the magnetics, and high latency for the processing. Even with the drawbacks, magnetic tracking is the preferred method.

Optical position tracking systems uses grid LEDs and a head mounted camera. The LEDs are pulsed in a sequence with the cameras image to detect the flashes so as to project the environment. Optical positioning is limited to spacing with the LED grid set up and the limit of rotation on the head mounted camera. Another method of optical positioning is using a number of cameras to capture images of an environment simultaneously to track objects.

Stereo vision
Stereo vision is the process of creating two different images of an environment, one image for each “eye”. The images are computed with the viewpoints offset by the equivalent distance between the eyes. The two images can be displayed sequentially on a conventional monitor or projection display. The user’s brain then receives the images in a rapid succession. It will fuse the images together into a single image with a perceived depth. This method is dependent on a higher display swap rate.

Another method to stereo vision is to use computer screens to split an image. The image will be divided into two parts and displayed on the monitor at the same time. One way to do this is to place the split image side by side or conventionally oriented (one above and one below). The image splitting may not take up the whole screen or it may alter the display ratio.



Head Mounted Displayed (HMD)
As is sounds, HMD is the use of some kind of helmet, goggle, or other mounted device to place a small display in front of the user’s sight. Most HMD’s use two displays, so as to provide stereoscopic imaging; however some HMD’s will only use one display, so as to display a higher resolution. Most HMD devices require a position tracker in addition to the helmet or goggle.
Hardware Levels
The entry level VR system is just a simple stock computer or workstation set and will normally implement a window on worlds system. The next level up is the basic level, and will have some system add on such as a basic interaction device and display device. An example of an interaction device would be a power glove or multidimensional mouse. The next level up is the advance VR level, which will add on a rendering accelerator for input handling. With the adding of an accelerator card, the system can improve dramatically in the rendering process. The advance level could also have a sound card added to improve audio output and/or voice recognition. The next level up is the immersion level. At this level, a VR system will have added some type of immersive display system, such as a head mount display, or large projection displays (much like the “cave” set up I mentioned earlier). One of the highest hardware levels is the cockpit simulator. In this level the VR system uses a form of Cab or compartment the user may enter to experience the 3D environment. The 3D environment is viewed through some kind of screen display. The cockpit simulator is most often used in aircraft simulators for training pilots, and to give the best training experience the cockpit will be placed on a motion platform to give a better sense of the environment.

Main Functional Module of a Virtual Reality Substation Simulation (fig.2)

Before any VR system can be created, it must first have a design. The main design of a VR system is the Virtual Reality Substation Simulation (VRSS). The data acquisition module is to acquire the original simulation parameters. Next, we have the Communication module to transmit the orders and messages between the different functional models. The simulation calculation module is used to calculate the simulation results according to preset mathematical model. The display module is for highly visible display of simulation processes and results vividly and directly by fully employing VR models of electrical devices, substation virtual scenes, 3D geometric graphs, data etc. VRS-engine is the basis kernel of the Virtual Reality Substation Simulation system, integrating different key VR technologies to provide technical support in the pattern of Application Program Interface (API) for the whole Virtual Reality Substation Simulation system.

The Kernel of a VRS-Engine (fig 3.)
The kernel is the most important part of VRS-engine, and provides the basic handling functions for VRS-engine. Components of the kernel can be classified as the following ones:



Objects Management is the inter-bus of VRS-engine; it manages all the things in VRS-engine and regards them as objects. Environment Modeling can set up a corresponding VR environment model for Virtual Reality Substation Simulation and then submit to View Prejudgment component. View Prejudgment can prejudge (judge before having good evidence) the visible parts of VR environment model observed by normal human sight and then submit to Scene Rendering component. Scene Rendering is responsible for depicting the basic 3D models and dealing with light and texture in the current and visible VR environment model and then generating VR environment. As one of the most important components in VRS-engine, it determines the performance of Virtual Reality Substation Simulation based on VRS-engine to a large extent. Collision Detection is an inevitable element of VRS-engine. It can catch the interaction-events triggered in the VR scene, and greatly determine the interactive ability of Virtual Reality Substation Simulation. Events Transaction can send different messages to the corresponding components according to different interaction-event. Script Compilation is data construction or language which can depict behavior of objects. Script in VRS-engine can be divided into 3 types:
A) Action Script, for modifying the location, direction and related attributes of objects;
B) Trigger Script, on an occurrence of interaction-events such as approach and touch, the script will trigger the relevant messages to deal with the event;
C) Connection Script, for the connection between output/input equipment and objects. It is much easier to control the electrical devices in VR scene with the help of these three scripts. This component compiles all the scripts for their exact execution.

Other Components of VR Kernel
Virtual Devices component provides many VR models with electrical devices. As an important segment of Virtual Reality Substation Simulation, Virtual Devices component is in charge of carrying and displaying messages in the process of simulation. However, this component is not a pure but compound (consisting of multiple devices), including:
A) Electric Model, receiving and storing simulation data and reflecting the main parameters of electrical devices such as voltage, power;
B) Geometric Model, displaying simulation messages and reflecting the appearance of electrical devices;
C) Behavioral Model, referring to the relevant interactive mechanism and the coordinating rules.
The Sound Effect component deals with the sound of VRS-engine such as sound effects of stereo to enhance the reality-sense of VR environments. Auxiliary Tools mainly include editors of electrical devices, VR model, and substation VR environments. They can edit virtual module visually and store its results in the data bank with the usage of editing instrument. I/O Interface is responsible for receiving control-orders from input equipments such as keyboard, mouse, joy stick or data glove, and in charge of administering input/output functions such as printing, import/export data, etc.

Internet Communication provides such functions as data transmission for VRS-engine.



Conclusion

VR systems are very detailed and versatile, with many different useful applications. However, even with everything described in this paper, VR systems are always changing and improving for the better. As technology continues to advance so will the uses of VR systems and the degree to which they are implemented. In time, even the average person will benefit from VR and all we can do is look forward to results of improvement.



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