# **AGAVE: Access Grid Augmented Virtual Environment**

Jason Leigh+, Greg Dawe, Jonas Talandis,

Eric He, Shalini Venkataraman, Jinghua Ge,

Dan Sandin, Thomas A. DeFanti

Electronic Visualization Laboratory

University of Illinois at Chicago

\+<spiff@evl.uic.edu>

## Introduction

The goal of AGAVE (pronounced agavay) is to augment the Access Grid to
allow collaborators to immersively share three dimensional content, such
as scientific and engineering data, in conjunction with their 2D Access
Grid content. AGAVE accomplishes this with a low-cost passive
stereographics projection system and accompanying networked PC.
Audiences will view the immersive content using inexpensive 3D movie
glasses. If desired an additional 3D tracking system and pointing device
can be incorporated to support 3D interaction. AGAVE can be deployed as
a separate display screen placed on one side of the Access Grid display
screens so that both standard 2D content can be viewed simultaneously
with 3D content.

## The AGAVE Hardware Configuration

The display system will consist of a pull-down polarization-preserving
silver screen, two LCD projectors with linear or circular polarizers in
front of each lens, a dual processor Linux driven PC with a high-end
graphics card capable of dual display output, such as the Evans and
Sutherland (E&S) Tornado 3000. To mediate the stereo, viewers will don
low-cost polarized movie glasses. Disposable glasses can be purchased in
bulk at a cost of approximately \$0.50 a pair or individuals may
purchase their own personal glasses for approximately \$12 a pair.
Circularly polarized filters and viewing glasses will cost slightly
more.

When 3D is not in use, the projectors and the silver screen can be used
as a standard powerpoint projection system hence providing additional
utility to the display system.

In choosing the graphics card for AGAVE the primary constraints were: 1.
Linux support on dual screens; 2. OpenGL acceleration under Linux for
dual screens; 3. performance; and 4. cost. Linux support is required
because our CAVERNsoft software, used to drive AGAVE, relies on
Performer, which only works under Linux and Irix. The E&S Tornado 3000
satisfies these requirements. The Matrox G450 is another possibility,
but up until recently, the Linux support did not provide OpenGL
acceleration on dual screens. We are currently in the process of
evaluating this card. The Intense3D Wildcat would have been the ideal
candidate if it were not for the fact that there is currently no Linux
support for it.

To support 3D tracking and interaction, Ascension Technology's Flock of
Birds (Extended Range Transmitter version), and EVL's Wanda can be used.
Wanda is a wand with an imbedded tracker, joystick and three buttons. It
is the standard interaction device used in CAVEs. The Flock is typically
driven by a Windows9X or Linux PC. An alternative to the Flock is
Ascension's pcBIRD. Whereas the Flock is a self-contained unit that
communicates with the PC via RS232, the pcBIRD consists of a circuit
board that plugs into 3 full-sized ISA bus slots in a PC.

## Projector Placement

Three projector configurations are possible. The first, and easiest,
stacks two projectors on top of each other. This solution requires
projectors that have integral shift lenses that are needed to converge
the images on each projector into the same area of the projection
screen. This solution is more costly (\>\$7500 per projector.) The Sharp
XG-E3500U is an example of projector with this capability. EVL has
already confirmed that this solution works.

The second and less costly solution uses standard powerpoint-style
projectors with factory fixed keystone offsets (\~\$5000/projector). In
this solution one projector is mounted on the ceiling, approximately
flush with the top of the projection screen, while the other is mounted
approximately flush with the bottom of the screen. Figure 1 shows the
display cones for two Proxima DX-1 DLP projectors mounted in this
manner. The intersection of the cones for each projector is where the
screen will be placed. The projectors are placed approximately 5' apart
(i.e. desktop to ceiling) to produce an image size of approximately 5\'
x 4\' at a 10' projection distance.

The third solution sacrifices display resolution for cost by attempting
to stack low-cost DLP projectors. Because of the factory fixed keystone,
the projection cones of the two projectors will not intersect perfectly.
To compensate for this the viewports for each eye's image needs to be
reduced and shifted vertically as shown in Figure 2. Unfortunately this
means that a portion of the display screen's resolution will be wasted.
EVL has confirmed that this solution works.

## Immersive Collaboration over AGAVE

## The CAVE library can easily be configured to work in dual-display mode under both Windows and Linux.

## To support collaboration in AGAVE, CAVERNsoft can be used. A separate CAVERNsoft server can be deployed at a known site. AGAVE participants will all launch their applications and connect directly to the known site. CAVERNsoft is a widely deployed cross-platform C++ toolkit to allow programmers to quickly develop collaborative, immersive virtual reality applications. Included with CAVERNsoft is an application called coanim (collaborative animator) that will allow collaborators to load up 3D data sets and begin collaboration immediately. Collaborators will see each other as avatars and may point at, rotate and scale the object being viewed. They may also cycle through a sequence of data sets to generate a 3D animation flip book. As Coanim is based on the CAVE library and SGI's Performer product, users on the Access Grid can interact in 3D with fully immersed participants in the CAVE and ImmersaDesk. Audio streaming will be supported by the existing Access Grid architecture. 

## Broadcasting AGAVE Visualizations

AGAVE visualizations can also be shared with Access Grid nodes that do
not have AGAVE systems. Images generated by AGAVE can be shared with
standard Access Grid viewers by feeding one of the AGAVE display signals
into one of the video inputs of an existing Access Grid node. A scan
converter (such as the Extron VSC 200) will be needed to convert the
AGAVE display signal to an NTSC signal. EVL is currently evaluating this
option.

## Cost Estimate

-   PC - \$5000-10000

-   Polarization-preserving silver screen -- 70"x70" - \$320

-   2 DLP projectors - \$10000 for low cost solution, \$15K-20K for
    higher cost solution.

-   100 pairs of glasses - \$50

-   Polarizing filters and projector mounts -- \$1000 (this is only an
    estimate- the cost will depend on the complexity of the mounting
    system.

-   Extron VSC 200 - \$3995

-   Wanda 3D Joystick - \$2560

-   Ascension Flock of Birds with extended range transmitter and 3
    sensors -- \$12580

-   Ascension pcBird with extended range transmitter and 3 sensors -
    \$11020

## References

# Intense3D Wildcat 4210 : <http://www.intense3d.com/4210/4210data.html>

Matrox G450 : <http://www.matrox.com/mga/products/mill_g450/home.cfm>

Evans and Sutherland (E&S) Tornado 3000 :
<http://www.es.com/wg/tornado.html>

CAVE Library : [http://www.vrco.com](http://www.vrco.com/)

CAVERNsoft : <http://www.evl.uic.edu/cavern/cavernG2>

Coanim :
<http://www.evl.uic.edu/cavern/cavernG2/modules/coanim/coanim.html>

SGI Performer : <http://www.sgi.com/software/performer/>

DLP : <http://www.dlp.com/dlp/default.asp>

Extron VSC100 : <http://www.extron.com/product/product.asp?id=vsc100>

Wanda 3D Joystick : <http://home.att.net/~glenmurray/>

Ascension Technology - Flock of Birds :
<http://www.ascension-tech.com/products/flockofbirds/>

Ascension Technology -- pcBIRD :
<http://www.ascension-tech.com/products/pcbird/>

![](media/image1.wmf){width="4.373611111111111in"
height="2.3777777777777778in"}

Figure 1 : Projection Cones for Two Low Cost LCD Projectors at
approximately 10\' away from the screen and separated by approximately
5\'.

![](media/image2.wmf)

Figure 2 : Stacked projector solution using low-cost LCD projectors with
factory fixed keystone offsets. Because of the keystoning the display
cones of the two projectors do not overlap completely. This is accounted
for by reducing the viewport for each eye's image accordingly.