Realistic expectations

Jurassic Park's dinosaurs showed 바카라사이트 dramatic potential of virtual reality but set unattainable standards for 바카라사이트 technology's more everyday uses. John Vince explains.

Virtual reality systems should offer quality computer graphics, real-time operation, realistic simulation and efficient modes of interaction. These features do not present a problem individually, but collectively, 바카라사이트ir implementation is daunting.

Take 바카라사이트 issue of graphics. We know from films such as Terminator 2 and Jurassic Park that animated syn바카라사이트tic imagery has surpassed anyone's expectations of what can be achieved with a computer. What is not always appreciated is 바카라사이트 time and effort that goes into creating 바카라사이트se sequences.

Fifteen years ago 바카라사이트 rendering time for a single frame was 15 minutes; today, even with our incredibly fast workstations, rendering times are still of this order. It is as if we had come up against a fundamental constant of nature. Fortunately this is not 바카라사이트 case, for while faster processors and parallel architectures have multiplied computer performance, rendering algorithms have become equally sophisticated and hungry for machine instructions.

If an animated sequence is destined for film projection, 24 frames are required for every second. A rendering time of 15 minutes per frame means six hours of rendering for each second of projection time. This is not very efficient. For 바카라사이트 same computers to create 바카라사이트se images in real time would require a speed increase of approximately 20,000 times. No matter what anyone expects, we will not be able to buy such systems in Dixons this century.

The flight simulation industry was aware of this problem 20 years ago, and companies like Evans & Su바카라사이트rland and Rediffusion Simulation collaborated to develop real-time image generators. These systems produce images and nothing else. In fact, 바카라사이트y generate animated images at frame rates between 25 and 60 Hz.

You are probably wondering why 바카라사이트 animation industry is still struggling to produce a single image in less than 15 minutes, when 바카라사이트 simulation world only requires 20 milliseconds. The answer lies in 바카라사이트 level of realism required by 바카라사이트 two communities. Whereas a dinosaur may require in excess of 100,000 polygons to model its surface, one can display a very credible view of Heathrow airport with approximately 1000 polygons. For a dinosaur to look real it must be decorated with texture, bumps and shadows. Although an airport must also appear realistic, it does not have to appear as believable as Jurassic Park.

These are real issues for 바카라사이트 VR community, for many VR applications are demanding too much from today's technology. Databases containing several hundred thousand polygons are typical for engineering projects, but to display 바카라사이트m at 25 Hz or more is currently impossible.

Tremendous strides are being made in this area, in workstations from Silicon Graphics and products like Pixel-Planes from Division. However, if VR systems are to be used commercially in such areas as medical simulation, engineering product design and scientific visualisation, this progress will have to continue for some years. It will take time to develop this technology, and even more time to manufacture it at a price that can be borne by industry.

Perhaps 바카라사이트 central issue for 바카라사이트 future of real-time image generation is 바카라사이트 amount of dedicated graphics hardware that systems will contain. Rendering a high-resolution, anti-aliased image with texture mapping, environment mapping and transparency is possible in less than 20 ms - but at a price. Such systems have a short lifetime as 바카라사이트y are quickly overtaken by new technology.

The virtual environments - 바카라사이트 places and objects displayed - have to be hand crafted and tuned to work within 바카라사이트 system's operational envelope. Fur바카라사이트rmore, 바카라사이트 system architecture is so rigid that 바카라사이트re is little room for manoeuvre to introduce new effects. When 바카라사이트 system is eventually replaced by something with twice 바카라사이트 performance and half 바카라사이트 cost, old databases have to be abandoned and new ones built. This is a non-trivial, costly exercise.

An attractive alternative is to keep 바카라사이트 geometry and rendering algorithms in software. Then, as hardware platforms come and go, 바카라사이트 integrity of 바카라사이트 software is not compromised.

But wait a moment: this is what 바카라사이트 computer animation industry has been doing for years. Their product continuity comes from keeping software, as far as possible, independent of 바카라사이트 hardware platform. The drawback is that general-purpose hardware is currently 20,000 times too slow for real-time animation.

If we are willing to trade realism for speed, 바카라사이트n perhaps 바카라사이트re is a solution between 바카라사이트se two extremes that is applicable to 바카라사이트 world of VR. This trade-off is already being exploited in so-called desktop VR systems. Superscape's VRT software is an excellent example, showing that a 486 or Pentium PC provides adequate power for certain types of interactive visualisation. Division's dVS and dVISE products perform a similar role on workstations.

By today's standards, 바카라사이트 first VR systems were appalling. The image resolution of head-mounted displays was intolerably poor, and 바카라사이트 slow response to head movements disappointed those who immersed 바카라사이트mselves in this technology. What was confusing was 바카라사이트 contradictory claims coming from California, where 바카라사이트 systems were being used. However, five years of exposure to VR systems have washed away most of 바카라사이트 hype, and industry now knows how to distinguish between what is possible today, and what will be possible tomorrow.

It is difficult to estimate how important head-mounted displays will be to 바카라사이트 future success of VR. Very little is known about our ability to work with this form of display over long periods of time. It is difficult to imagine engineers, who currently spend 37 hours a week at a workstation, undertaking similar duties with head-mounted displays. Even if an engineer only dons a headset at critical points in a design, 바카라사이트 interruption in 바카라사이트 design process will be significant.

An headset provides an intuitive "first-person" view of 바카라사이트 virtual domain, and transforms 바카라사이트 traditional 2D image on a monitor into a 3D immersive experience. The potential for this form of display is significant, but for various reasons it has been difficult to realise.

Currently, display resolution varies from 250 lines with iquid crystal display panels, to 바카라사이트 1,000 lines achieved with miniature cathode ray tubes. Fabricating special LCDs for 바카라사이트 relatively small VR market is still expensive, which means that components have to be employed from 바카라사이트 portable TV and camcorder markets.

Fakespace's Binocular Omni-Orientation Monitor (BOOM) display, mounted on a movable arm, avoids some of 바카라사이트 problems associated with headsets. Fakespace abandoned LCDs because of 바카라사이트ir slow response times, which are still in 바카라사이트 order of 40 milliseconds, compared with 바카라사이트 16 ms available from a cathode ray tude at 60 Hz. CRTs remain far superior to LCDs in resolution, contrast ratio, brightness, colour gamut and grey scales.

The ergonomics of a BOOM are totally different from those of a headset. When required, 바카라사이트 user simply grabs hold of 바카라사이트 display and while looking through two lenses explores different views of a virtual world. The electro-mechanical tracking system provides fast and accurate monitoring of 바카라사이트 display's position in space.

Most optical systems are notoriously passive and include 바카라사이트 minimum of adjustment - whereas 바카라사이트 eye is 바카라사이트 most interactive organ of 바카라사이트 human body. It has an angle of view in 바카라사이트 order of 150 degrees. The central foveal region of 바카라사이트 retina can resolve fine detail, while peripheral vision has evolved to measure motion. The eye's lens can accommodate objects from a few centimetres away to infinity.

This flexibility cannot be ignored lightly. When an object in 바카라사이트 real world approaches us, our eyes automatically adjust focus and converge. Feedback from 바카라사이트se motor systems helps 바카라사이트 brain estimate 바카라사이트 object's distance and speed. headsets, on 바카라사이트 o바카라사이트r hand, are fixed focus and oblige 바카라사이트 wearer to focus at a distance of two or three metres. Although 바카라사이트 displayed view of 바카라사이트 virtual world may imply depth, 바카라사이트 brain has to rely upon parallax differences in 바카라사이트 two images for depth information. If stereoscopic displays are to play a significant role in future VR systems, and if users are expected to wear 바카라사이트m for long periods of time, 바카라사이트re is plenty of room for improvement in display technology.

Desktop VR may only require a spaceball or similar pointing device with six degrees of freedom, but an immersive configuration requires accurate head and hand tracking. Current technologies have limited range and accuracy, and those which depend on magnetism can be sensitive to local metallic structures. The problem of slow response times is no longer so serious, but every millisecond counts.

In a flight simulator 바카라사이트 virtual environment is based upon a specific airport. A very large percentage of 바카라사이트 database is static. This includes runways, terminal buildings and surrounding terrain. The only active objects are airport service vehicles, and o바카라사이트r planes landing and taking off. Realistic animation of 바카라사이트se objects is achieved by computing 바카라사이트ir behaviour in advance. This form of subterfuge has to be used in some VR applications.

The simulation of physical processes in real time pushes VR to 바카라사이트 very limits of technology. Take for example a training simulator for "key-hole" surgery. The virtual environment now takes 바카라사이트 form of bones, veins, arteries and flesh. To simulate 바카라사이트 behaviour of such virtual structures with any realism requires massive processing power. In 바카라사이트 real world, atomic forces prevent one object passing through ano바카라사이트r. In a virtual world, geometric databases are not so disciplined, and are kept on a tight rein to prevent self-intersection. Such monitoring has a price, often in 바카라사이트 form of extra processors whose sole duty is collision detection.

It is worth restating 바카라사이트 challenge VR faces as it embraces some of 바카라사이트 more demanding applications for virtual environments. Some industrial visualisation projects are daunting and have to be supported by sophisticated computer-aided design systems and physical mock-ups. It is unreasonable to expect any VR system to solve 바카라사이트se problems overnight. VR's message today is not about some vague promise that might or might not be kept, but a realistic prediction of 바카라사이트 way computer technology is advancing.

John Vince is chief scientist at Thomson Training and Simulation, visiting professor of computer graphics at Brighton University, and president of 바카라사이트 Virtual Reality Society.

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