Immersive Visualization / IQ-Station Wiki
This site hosts information on virtual reality systems that are geared toward scientific visualization, and as such often toward VR on Linux-based systems. Thus, pages here cover various software (and sometimes hardware) technologies that enable virtual reality operation on Linux.
The original IQ-station effort was to create low-cost (for the time) VR systems making use of 3DTV displays to produce CAVE/Fishtank-style VR displays. That effort pre-dated the rise of the consumer HMD VR systems, however, the realm of midrange-cost large-fishtank systems is still important, and has transitioned from 3DTV-based systems to short-throw projectors.
3D Displays
3D Display Technologies
It was the introduction of consumer-level (aka COTS) 3D Displays in 2007 that was the primary catalyst that made-reasonable the ability to construct a VR display affordable to small research efforts.
Since the introduction in 2007 of Active-stereo DLP TVs from Samsung and Mitsubishi, there have been a multitude of products released, using a wide variety of technologies. Not all of these consumer-3D technologies work well as VR displays however. Thus here we will sort out the advantages, disadvantages and disqualificating features of each.
Features to evaluate include active vs. passive stereo, auto-stereo, LCD vs. plasma technologies, and more.
Method of Stereoscopic presentation
The two primary methods of presenting separate views to each eye (Stereoscopy) are frequently referred to as Active and Passive stereo. These names refer to the need (or not) for active electronics contained within the eye-glasses used to separate the left and right views. A third technology uses thin barriers placed at the screen to direct the left and right views in particular directions, allowing users to position their eyes such that no glasses are required for the stereoscopic pair. This glasses-free technology is referred to as auto-stereo displays. A fourth method of presenting stereo that certainly falls into the realm of low-cost is the color-filter based method referred to as Anaglyphic stereo. Anaglyphic stereo is still useful in a pinch, but is not recommended as a technology for daily 3D viewing.
Active Stereo
Systems using active stereo glasses have long been the mainstay of the virtual reality (and indeed scientific visualization) community. For many years, the company StereoGraphics sold a line of glasses known as "CrystalEyes". These glasses were used in CAVE-style VR systems throughout the world. There are now many manufacturers of 3D Active viewing glasses, including many of the television manufacturers.
Pros of Active Stereo
- Higher frequency displays may render full-resolution
Cons of Active Stereo
- Systems using infrared (IR) to transmit signal to glasses can interfere with IR of tracking systems and remote controls
- More expensive
- More fragile
- Require battery replacement (or recharging)
Passive Stereo
Passive stereo systems have become the standard for theatre 3D presentations, and are growing in use for home 3D systems. Passive stereo works by multiplexing a stereoscopic pair of images through some form of light filter. The glasses then use simple optical filters to allow only the image for the desired eye to pass through the view. Light polarization is the technique typically employed by consumer 3DTVs. The other common form is the use of color filters. Color filters can range from the simple red/blue (anaglyphic) style to the more sophisticated Infitec multi-hue method.
Because polarized-light is used in most public theater 3D systems, passive 3DTV's are frequently marketed as "Cinema-style" 3D. However, the method of transmitting polarized-light passive stereo differs between theater and home. In the theater, the left & right images are shown simultaneously, allowing each image to be presented in full resolution. On a 3DTV, a technology called Film-type Pattern Retarder (FPR) is used, which dedicates alternating rows (or sometimes columns) to one eye or the other — thus reducing the physical resolution by half. (However, some experiments on perception suggest that the existence of redundant information in the two images leads to a result that is not as poor as 50% resolution.)
Pros of Passive Stereo
- Less expensive to purchase (can even use glasses obtained attending a 3D movie)
- Less expensive to maintain (don't break as often and no batteries)
- Do not interfere with other IR-based technologies (e.g. tracking and remote controls)
Cons of Passive Stereo
- FPR technology reduces resolution
- NOTE: However, not all active stereo provides full-resolution either
Method of Stereoscopic Rendering
Rendering (as opposed to displaying) is how the 3D image is created. This image is then transmitted to the screen. There are a handful of techniques used to relay this 3D information to the screen.
Time-interlaced
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Side-by-side (or tom/bottom)
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Checkerboard
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HDMI 1.4 (left/delta)
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Experience with Specific Models
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