Pro AV Magazine, KS
09-01-07
Education Install: 3D Simulation to the Max
The modernized C6 at Iowa State University sets new precedent for immersive
virtual reality systems.
by Katie Parrish
Challenge:
Update a six-sided virtual reality system to meet today’s needs and lead it into
the next generation.
Solution:
Design a system that employs the highest resolution projectors available and one
of the world’s largest graphics computer clusters.
[Left: Viewers experience a 100 million pixel virtual cell simulation, partially
funded by National Science Foundation grants, in the C6, located at Iowa State
University’s Virtual Reality Applications Center.]
Immersive virtual reality enables a broad range of researchers to overcome
challenges posed by space constraints, scale, or time variances. Biologists use it
to shrink themselves down to the cellular level. Manufacturers apply it to
developing new products and managing business models. The military employs it
to train for real-world combat.
At Iowa State University in Ames, Iowa, the Virtual Reality Applications Center
(VRAC) is at the forefront of virtual reality technology. In 2000, VRAC opened the
C6, the first six-sided immersive virtual reality system in North America. A new
variation CAVE design (Cave Automatic Virtual Environment, see sidebar), the
C6 is a 10-foot-by-10-foot-by-10-foot room in which computer images are rear
projected on soft vinyl screens supplied by Stewart Filmscreen on all four walls
and the ceiling. A single 2,000-pound, 2 3/4-inch thick piece of optically-correct
acrylic allows images from the bottom projector to appear on the floor. One of the
wall screens is mounted on a pneumatically actuated frame to allow for access to
the C6.
Likening the 3D virtual reality experience to a very sophisticated version of a
child’s Fisher Price ViewMaster, in which the circular disk shows one image for
the right eye and another for the left, Dr. James Oliver, director of VRAC, says
the brain fuses those images together to make them appear three dimensional.
“You don’t see the edges of the boundaries; the walls just melt away, and objects
come at you from outside or go out to infinity, he says. However, this vision is
difficult to convey in a photograph or video because it becomes only two-
dimensional. “Without the stereo effect, it looks like a big box with lights on the
walls,” he adds.
For its first five years, VRAC’s C6 was one of most widely used virtual reality
systems in the world. But by 2005, Oliver says that every performance dimension
of the C6 needed improvement. “It had some unique innovations in its day,” he
says. “But five years is a long time in technology.”
Securing nearly $5 million in funding from the U.S. Air Force Research
Laboratory to upgrade the C6, VRAC set out to solicit bids for the project in mid2005. VRAC received five bids for the project and selected Fakespace Systems,
the display system integration division of Marshalltown, Iowa–based Mechdyne
Corp., as the installer for the C6 updates in January 2006. Mechdyne was the
original installer on the C6 project in 2000. Updates on the system began in May
2006.
Visual Solutions
In its detailed functional specifications, VRAC required that the new solution be
capable of producing a minimum of 4 megapixels at a resolution of 2000 x 2000
per wall for a density of 16.67 pixels per inch. Knowing that increased resolution
was high on the list of priorities, Kurt Hoffmeister, vice president of engineering
for Mechdyne, says his company wanted to offer VRAC a solution that far
exceeded this minimum requirement.
Fakespace incorporated 24 SRX-S105 SXRD projectors, manufactured by Sony
Electronics, in the update. Introduced in July 2006, the SRX-S105 ultra highresolution projector — one of four units in Sony’s SXRD projector series — was
specifically designed for large-venue and high-resolution applications. The 4096
x 2160 resolution of this projector is four times greater than the highest definition
television currently available to consumers. On the 10-foot-by-10-foot walls of the
C6, pixel density is greater than 34 pixels per inch, and with a total 24 projectors,
the system achieves a 100 million pixel stereoscopic display, which is 16 times
greater than C6’s original display. Of the initial $5 million bid, the facility and
technology upgrade — including projectors, electronics, and optics — made up
more than $3.5 million of the cost.
[Left: A diagram of the C6 structure, showing the framework and image overlap
requirements. ]
Fakespace knew that the only way to meet VRAC’s resolution requirement and
support stereoscopic viewing with the current technology available was to
provide multiple projectors per wall. Four projectors were stacked vertically for
each surface, reaching about 10 feet high. “Two blend together to make up a
4096 x 4096 right eye image, and because it is stereoscopic, the other two
projectors are providing the left eye image,” Hoffmeister says. “Because the
projectors have to overlap each other to produce a square image, we’re using
Fakespace’s own version of optical blending.”
Graphics Generator
Driving the C6 is a 96-channel workstation cluster — four separate graphic inputs
for each projector — that was configured and installed by VRCO, the software
division of Mechdyne. According to Matt Szymanski, vice president of VRCO, the
cluster is comprised of 48 separate HP xw9300 workstations, each with two
graphics outputs, plus an additional workstation to serve as a master node that
houses the application and interaction software.
“Each workstation is responsible for generating an image for one-eighth of a
given wall,” Szymanski says. “Each video signal coming from a PC is at the
slightly greater than HD resolution of 2048 x 1080. Therefore, each wall is
comprised of eight PCs generating two contiguous images — one for the left eye
and one for the right eye — of 4096 x 4096 resolution, or more than 16 million
pixels per side of the C6.”
Viewer Tracking and Sound
Providing the sound for the C6 is a custom, eight-channel audio system.
Components include an M-Audio Delta 1010 computer multi-channel audio
interface; Peavey MediaMatrix X-Frame 88 audio DSP mixer/processor and MM8802 audio mixer/processor interface, and A/A-8P audio preamplifier; five Extron
BUC102 audio balanced-unbalanced converters, and one pair of JBL Control
25AV loudspeakers. Existing audio equipment carried over from the original C6
design include two ATI1604 four-channel power amplifiers, three pairs of M&K S85TV speakers, an M&K MX-5000 MK II THX subwoofer, and an Audio
Technologies BU400 balanced-unbalanced converter.
[Right: The C6 computer cluster is made up of 49 HP workstations; 48 provide
two graphics outputs and one serves as the master node. ]
“I guess you would describe it as 8.1,” Hoffmeister says. “Basically, there are
eight channels of sound plus a sub. There is essentially a speaker in each
corner, so the four upper corners and four lower corners have a speaker and can
generate some directional sound when you’re inside the cube.”
A critical portion of the C6 is the viewer tracking system, which links the
computer visualizations to the viewer’s point of view. “Where they’re standing
and where they are looking affects what is drawn,” Hoffmeister says. To enhance
the viewer’s experience, Fakespace incorporated inertial-acoustic IS900 tracking
equipment from InterSense of Bedford, Mass. The viewer wears two or three
sensors — one for the head and one or two for the hands — and built into the
display are a series of small emitters that put out a signal that the tracker picks
up on. From there, the computer application knows the person’s location inside
the C6. “What makes the whole experience so immersive and interactive is that
the graphics are being drawn for your head position and point of view, and then
with your hand position tracking, there’s a certain amount of interaction as well,”
Hoffmeister says.
Tweaking the Design
One of the C6’s most innovative features — the projector stack — was also one
of its greatest design challenges. “Where before we just had one projector for
each surface, now we have four of them,” Hoffmeister says. The real installation
challenge came with the floor and ceiling. On a catwalk above the system, the
projectors are reflected off mirrors to illuminate the ceiling, and the same goes for
the floor. “Just mounting that much additional equipment became a challenge,”
he says. “Each projector weighs a little over 240 pounds, and there were a
variety of safety issues with lifting and mounting that equipment overhead.”
Adding a substantial number of projectors increased the C6’s brightness, but also
led to heating/air conditioning and electrical challenges. While ventilation for the
machine room housing the computers was specified in the design, the projectors
also were emitting a significant level of heat, Oliver says, which was initially
overlooked in the design plan. “We worked with our facilities people to add more
HVAC in the C6 enclosure itself,” he says, which added an additional expense
and delayed the construction schedule.
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