Low-Cost VR

In the past, 3D stereoscopic displays and 3D tracking systems have kept the prices of fully immersive VR environments very high. Recently, however, new commodity technology has become available, and it is now possible to build a fully immersive VR environment, i.e., a head-tracked stereoscopic display system with tracked input devices, for about $7000. This web page documents how to assemble one such system, based on a 3D-capable high-definition DLP projection TV, such as those offered by Samsung or Mitsubishi, and the NaturalPoint OptiTrack optical tracking system.

Figure 1: A quartz crystal being manipulated using the Nanotech Construction Kit on a Samsung 3D TV and a tracked Wii controller. The "tracking antler" mounted on the Wii controller, consisting of three retro-reflective balls, is picked up by the optical tracking system to determine the controller's position and orientation in space.

Low-low-cost VR

With the release of the Razer Hydra 6-DOF desktop input device, it is now possible to build even lower-cost entry-level VR environments. While not head-tracked, and therefore not immersive or "holographic," these are still very useful for a wide variety of 3D applications, such as the Nanotech Construction Kit as shown in this video and in Figure 2. The only required components are a graphics-capable PC, a 3D TV, and the Razer Hydra (for around $150). See the installation instructions.

Figure 2: A low-low-cost VR environment using a 3D TV and a Razer Hydra 6-DOF desktop input device.

Stereo Quality

One of the more important factors when deciding what 3D TV to buy is stereo quality; unfortunately, this is also the most difficult to evaluate, because it is typically not mentioned in the specifications for a particular TV model, and it cannot easily be gauged by viewing a TV model in a showroom. This is because typical 3D content is low-contrast and has low eye separation, following the "standard" guidelines for 3D content. These guidelines originate from rules of thumb put up by people who are doing stereo wrong, and tried to minimize the ill effects of their fundamentally flawed approach by "flattening" the 3D images they display. It's a long and sad story. Anyway, using 3D TVs as we do exposes limitations of the technology that the manufacturers might not even be aware of.

By "stereo quality" we primarily refer to the amount of cross-talk between the displayed left and right eye images. Ideally, cross-talk should be 0%, in which case left and right eye images are completely separate. In non-zero crosstalk, images from one eye show up more or less faintly in the other eye, which causes problems when the viewer's brain tries to fuse the two images into a 3D view. The more cross-talk there is, the more difficult is it for the viewer to perceive the 3D effect, and at some viewer-dependent level of cross-talk, 3D breaks down completely.

Cross-talk is caused by both the TV, and whatever eyewear is required to view the TV. In active (time-interleaved) stereo, it is caused by the TV's ability to switch between images rapidly, and by the active shutter glasses' ability to switch between opaque and transparent rapidly. On the TV side, projection DLP TVs have 0% inherent cross-talk, because the main benefit of the DLP display technology is its ability to switch between images extremely rapidly. LCD-based TVs have inherent cross-talk because the per-pixel LCD elements cannot switch rapidly enough. Active shutter glasses use (large) LCD panels as well, and have the same problems. Polarization-based "passive" 3D TVs use polarization filters on the display, and polarized glasses, to create separate left/right images. Here cross-talk is caused by the less-than-perfect polarization filters on both ends.

Evolution of 3D TV Technology

The first generation of 3D TVs were all based on DLP projection technology, since their 3D capability was an incidental side effect of the then-current method of creating a 1920x1080 HD picture with a micromirror with only half as many pixels using a method called "wobulation." These days, there are several types of 3D TVs based on different combinations of technologies:

DLP projection TVs using wobulation and active stereo: These are the first-generation 3D TVs mentioned above, and shown in the pictures on this page. Pros: large screen area for low cost, very good stereo quality (dependent on shutter glasses), can use 3rd-party shutter glasses. Cons: low brightness, limited viewing angle, bulky footprint.
LCD-based flat panel TVs using active stereo: These are the most common 3D TV models right now. They rely on fast-switching LCD panels that can generate different images at around 120Hz refresh rate. Pros: high brightness, good viewing angle, small footprint, low power use. Cons: higher cost per screen area, worse stereo quality due to higher cross-talk, typically only work with proprietary per-model shutter glasses.
Plasma-based flat panel TVs using active stereo: These are not very common anymore, but they are typically cheaper than LCD-based TVs at the same screen area. We cannot give much details about their performance as we have never tested one in-house. Pros: high brightness, good viewing angle, small footprint, potentially good stereo quality. Cons: higher power use, danger of "burn-in."
LCD-based flat panel TVs using passive stereo: This is the most recent technology, and its main benefits are potentially better stereo quality due to use of polarization instead of active switching, and their use of cheap polarized stereo glasses. Passive 3D TVs rely on interleaving, where alternating pixel rows have opposing polarization. The main drawbacks of this approach are that it reduces vertical resolution, and limits vertical viewing angle. Viewers have to be located in a horizontal plane going through the TV's center in order to get a proper stereo effect. Moving away from this ideal plane causes linear increases in cross-talk up to 100%, after which stereo flips. Pros: high brightness, small footprint, low power use, decent stereo quality, cheap unpowered glasses. Cons: reduced vertical resolution, limited vertical viewing angle.

The bottom line is that there is no clearly superior technology; all stereo methods have their drawbacks. Picking the proper TV model is a matter of what exact setup one has in mind, what screen size and footprint is desired, and how much money one has to spend. The good news is that all technologies listed above are supported natively by our software, and work out-of-the-box.

News

Fry's recently had a 70" Sharp LED/LCD 3D TV on sale for about $2200 (update: out of stock now). This is a steal for a flat-panel TV of this size. The same model is still available at Amazon, but for $3100.
Just last Saturday (12/06/2008), I saw a 73" Mitsubishi 3D TV for sale at the CostCo in Woodland, CA, for $2099 including a matching stand. That's a steal, compared to the 72" Samsung HL-T7288W with stand at Amazon.com for about $3000 (see shopping list). I have not seen the Mitsubishi in 3D mode, but it should be just as good as the Samsung.

Pages In This Section

Pictures: Some pictures and movies showing our prototype low-cost VR environment.
Shopping List: List of all hardware components required to build a low-cost VR environment, with links to online vendors where available. Note: The list is somewhat outdated, as there are now too many options for 3D TVs to cover them all. The good news is that any commercially available 3D TV will work out-of-the-box, with some caveats regarding stereo quality (see paragraph above).
Installation Instructions: An evolving and very detailed document describing how to install and calibrate a low-cost VR environment.
Calibration Utilities: Page describing several utilities to calibrate a low-cost VR environment that are bundled with the Vrui VR toolkit.
Low-Low-Cost Installation Instructions: An evolving document describing how to install and calibrate an even lower-cost VR environment based on a Razer Hydra 6-DOF desktop input device.