Tomorrow's Treasures, Day 4 - SIGGRAPH 2006

Wednesday, August 2, marked the fourth day of activity at ACM's SIGGRAPH 2006 graphics and animation conference in Boston, and after all the commotion of the initial days of the show, yesterday saw attendees finally settling into a routine. Though the convention remained a constantly bustling hive of technological revelation and wares-peddling, the amazed faces so abundant during its first few days were replaced with visages of introspective interest in the future of technology.

As I mentioned in my last post, much of the content in the various exhibition halls at SIGGRAPH falls into a few recognizable subcategories of what is admittedly a very broad 'graphics' theme. Having already covered examples of next-generation input devices and future developments in game-related technology, I thought I'd spend some time today touching on the show's 3D VR offerings.

One of the more frequently-used technologies in the realm of VR here at SIGGRAPH is a subsonic noise-based tracking system developed by a company called InterSense. Though several booths were showing off giant VR screens for various marketing purposes, they all used InterSense tracking systems to allow users to interact with their virtual wares. The tech works by implementing a set of three tracking bars on the top and sides of a given VR screen (itself little more than a rear-projection screen about 10 feet diagonally). Each bar both emits and receives sonic waves to and from a pair of wireless devices: a glasses-mounted sensor to track eye position (and thus modify a projected VR image on the fly to align it perfectly with the user's eyes) and a handheld sensor attached to an interacting pointer device. In order for the pointer to emit a virtual beam on the screen, giving it a presence in the virtual world, InterSense's sensors must track its location and orientation so that its virtual reflection can be displayed to match.

Thus, when a user pops on a pair of stereo glasses and grabs the pointer, a virtual beam of light is "emitted" from its tip, perfectly aligned no matter where the user is standing or the device is held. Given a virtual representation of a human heart, for instance, a user could hold the pointer horizontally, casting its beam in front of the heart, and then literally step forward, swing the beam around, and cast it through or behind the heart. The effect is startlingly convincing, as though you're moving a handheld pointer around and behind an actual three-dimensional object, pointing at (or modifying at will) different parts of it.

Different VR projectors are provided by different companies and paired with different kinds of eyewear, even though InterSense's technology is used for tracking purposes almost universally. There are two different kinds of stereo projection techniques: passive and active. Passive stereo is what you're probably used to: two projectors simultaneously emit images to the screen, but each projector emits polarized light at different angles. A user wears a pair of polarized glasses to view the image, so that each eye is fed a view from a different projector. Assuming that the distance and angle of the two projected images are calibrated correctly to each other and the viewer (helped along under optimal conditions by one of InterSense's glasses-mounted trackers), you end up with a very decent 3D image. IMAX uses such technology to full effect every day; here at SIGGRAPH, Purdue University is using passive projectors to drive a VR flythrough of its entire campus.

Active stereo, however, takes things a step further than their counterparts. A single projector emits a flip-flopping image to the VR screen, toggling back and forth between the view designed for one eye and the view designed for the other. The user wears special glasses that have tiny shutters in the lenses, opening and closing in time with the projector (which, as you can imagine, is far too fast for the eye to notice). The left shutter opens to view the left image exactly when the projector displays it, and then the process shifts to the right eye. Back and forth, dozens of times a second, and you end up with a 3D image that doesn't suffer from the slight hazing that passive stereo is so often plagued with. InterSense itself is using active stereo at its booth here at SIGGRAPH, as is Barco -- though the latter company has taken things a step further than anyone else by providing six-sided VR cubes for highly immersive experiences.

Screen-based VR is definitely a glimpse of the future of interactivity, but it's not the most immersive solution available. Thursday is the last day of SIGGRAPH 2006; be sure to stop by tomorrow for a wrap-up of the convention's offerings, and an interesting discussion: how the combination of technologies offered by three different organizations could be potentially used to create the ultimate, fully immersive, fully tactile 3D virtual experience. It's not quite perfect yet, but it is there, and it's getting better and better.

See you next time. Dan out.

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ACM SIGGRAPH 2006 Coverage:

• Tomorrow's Treasures, Day 1
• Tomorrow's Treasures, Day 2
• Tomorrow's Treasures, Day 3
• Tomorrow's Treasures, Day 4
• Tomorrow's Treasures, Day 5