The tracking camera that's mounted to the bridge of the castAR frames has a FOV of 110 degrees.
The tracking targets are made up of five IR LEDs. They're arranged in a square pattern with the fifth LED offset diagonally a short distance from the lower left corner. The fifth LED does two jobs - it identifies the lower left corner of the tracking target (and thus its orientation) and its output is modulated by a cheap micro-controller. This allows individual tracking targets to be identified.
Technical Illusions will be releasing the modulation method for the tracking targets so people can build them if they don't want to buy them - the system is simple enough that you could build one for about $7 at the high end.
castAR can track up to 200 targets - I suspect because they're using an 8 bit modulation code which would limit the total to 255 combinations and they're reserving some for "internal" use.
If you want to build a complete 360 degree environment, you would place a tracking target about every 90-100 degrees to give yourself a bit of overlap. This would pretty much ensure that no matter where you looked, you'd ever lose tracking. Because they're going to be including an IMU as well, even if the tracking camera were to lose sight of the available targets, the IMU could take over until such time as the camera was able to re-acquire a target.
Tracking is handled by an FPGA (currently - an ASIC will be created for the production model once the feature set is set in concrete) mounted to the castAR. This keeps all the tracking load on the castAR and not on the host, which makes for very, very fast tracking. I don't know what the actual latency is, but I've read that it's as-good or better than the currently published figures for the Rift. Tracking data is passed to the host via USB cable and according to Jeri & Rick's interview on Triangulation (
http://twit.tv/show/triangulation/124) the data packets are 72 bytes long. I don't recall what the data rate is however. (Watch the episode, it's got a lot of good information in it by the people that created it.)
castAR connects to the host via HDMI cable for video. The host considers castAR to be a single 2560x720 display. The current version of castAR utilizes two 720p pico projectors mounted over the center of each eye. The projectors put out a very low level of light. So low that unless you're looking at a retro-reflective surface, you won't see the output of the projectors. However, with RR material, the output is clean and bright, even in normal room lighting. The reason this works like this is because the retro-reflective surface (essentially the same fabric used for safety stripes on clothing) has a very, very narrow angle of reflection. This means that nearly all the output from the projectors is reflected directly back at the source with very little loss due to scattering effects. This phenomenon allows more than one castAR user to share the same retro-reflective surface without causing display interference. For example, given an RR surface on a table and one tracking target, user two can sit shoulder to shoulder with user one and they'll both see the same thing, from slightly different angles (due to the horizontal offset from the tracking target) and there won't be any image "contamination" from the projectors. Tandem use is also possible, so you fast-mover fans could actually build a tandem cockpit with a practical and affordable video system.
I don't recall what the exact horizontal FOV is, but it's the _actual_ FOV from the projectors, not optically modified as with the Rift. (With the Rift, you're looking at two "halves" of the same LCD panel and its internal optics are broadening what you see, so all the raving about how the Rift's FOV is so much better than x, y or z is mostly nonsense.) castAR utilizes LCD shutters that operate at 120Hz to give the "3D" effect. Each shutter operates at a 50% duty cycle and the projectors have some small percentage of overlap (I don't recall the exact figure.) and each eye "sees" a full 1280x720 image. (There's more going on with the system at this level, but I don't recall the details - I think most of it is covered in the Triangulation episode I link to above.)
castAR also has a VR "clip-on" which is essentially a special pair of lenses that fit on the face of the castAR and reflect the output of the projectors into your eyes. I know very little about this feature because it's not my area of interest.
Finally, the target weight of castAR is 100g and it doesn't interfere with glasses.
Questions?
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