The Geowall Hardware List

The Geowall can be assembled from off-the-shelf components that include, minimally, a PC or Mac with a decent dual-head graphics card, two DLP projectors, polarizing filters with matching glasses, and a screen that preserves polarization. The sections below describe in some detail the type of hardware many in the Geowall community use with remarks on exchangability. We also list a number of vendors that we have used, who have been beneficial in keeping the price of components down. In addition, they know the ins and outs of the geowall setup or stereo projection, and we recommend new Geowall developers to use their expertise to save time and money.

Projectors
Screens
Polarizing Filters and Glasses
Linear Polarized Filters
Circular Polarized Filters
Linear Polarized Glasses
Circular Polarized Glasses
Projector Stackers
Filter Holders
Computers
List of Tested Graphics Boards
Stereo Cameras
Carrying Cases

Projectors

Manufacturer: NEC and Panasonic
Vendors: Zach Boxrud at Projectorpoint.com

Most DLP projector will allow polarization (LCDs generally won't). Most GeoWalls have been built with the InFocus LP530 and more recently NEC LT240K projectors. The current models that have been tested and approved by the manufactures are...

NEC LT240K/LT245
2000/2200 Lumens, XGA resolution, 2000:1 Contrast

NEC LT265
2500 Lumens, XGA resolution, 1600:1 Contrast

Panasonic D-5500
5000 Lumens, XGA resolution, 1600:1 Contrast

Other projectors may work, but it is important to keep in mind that DLP projectors run VERY hot. The approved projectors above can tolerate stacking, but other projectors can overheat. They may shut themselves down after 10-30 minutes because of inadequate cooling. Some manufactures may not honor warranties for unapproved projectors used in stacked systems.

Screens

Manufacturers: Stewart and DaLite
Vendors: Zach Boxrud at Projectorpoint.com

This system requires that the light from the projector be polarized. The screens must preserve the polarization. Low-cost, portable, front projection screens from Da-Lite will work fine. They are not best with ambient light in the room but work fine in a semi dark room. Remember to buy a carrying case or a ski bag if you are going to move them a lot.

We have found the best screens to be from Stewart Filmscreens, Inc. Both front and rear projections are available. Talk to Rob Gag or Zach Boxrud at ProjectorPoint.com about sizes, prices and delivery times. We've found it to be much easier to talk to Zach or Rob than to try to buy them from Stewart Filmscreens directly. If you want to do rear projection you need to worry about the size of the room (you need a few meters behind the screen for the projectors and a few meters in front for your audience) and setting up the screen. The standard rear projection screen comes with a frame but without a stand; talk to Zach or Rob about ordering the stand and screen together unless you feel like constructing a stand yourself.

Polarizing Filters and Glasses

There are a number of different options available to filter your passive stereo projection system. We have found the simplest process is to talk to Zach at projectorpoint.com. He carries all of the filters, filter holders, and glasses you will need.

Linear Polarized Filters

Manufacturers: Hoya and American Polarizers, Inc.

Some Geowallers use the Hoya 72mm PL linear polarized camera filters. These filters will thread right on to the lens of the NEC LT240K and LT245 projectors. However be cautious that this type of set up can burn out the filters very quickly, and you may be replacing filters often. This type of setup is nice for traveling with your Geowall, and just threading the filters on to the projector lenses. These filters can be found at any local camera store.

We recommend using the Linear Polarizing Square Filters from American Polarizers, Inc. There are a number of ways to mount these in front of the projectors, but the easiest way is to use the custom filter mounts available from Zach at projectorpoint.com.

Circular Polarized Filters

Some of our more picky GeoWall users have gone to circular polarization so that you can tilt your head farther when looking at a GeoWall. Michael Redmond of the eMedia Center at the University of Wisconsin has written a very good white paper about how he did it. Some people say the circular polarizers give you a better filtered image than the linear polarizers.

Order the following:

Glass circular polarizers
Filter size to order should be calculated as: sqrt(Lumens / 145) e.g. if you have a 2000 lumen projector, you should order sqrt(2000/145) = 3.7in x 3.7in (round it up to 4in).
Thickness should be: 0.115 inches

From:

American Polarizers, Inc.
141 South Seventh Street Reading, Pennsylvania 19602 USA
Toll Free: 800-736-9031 · Tel: (610) 373-5177 · Fax: (610) 373-2229
Mary Lorah (mlorah@apioptics.com)
http://www.apioptics.com/3d.htm

Linear Polarized Glasses

Vendors: Reel3d.com
Craig T. Jones, American Paper Optics, Inc.

Linear Polarization Glasses are the cheapest and most common polarized (gray) glasses available. This is what you use at Disneyland or an Imax theater. They cost between $0.50 and $3.00 a pair depending on volume and type (paper/plastic.)

If you are using your GeoWall in a classroom we suggest you use Theme Park style plastic glasses. They are rugged, cheap and stylishly nerdish.

Circular Polarized Glasses

Craig T. Jones also carries the circular polarized glasses.

Projector Stackers

Manufacturer: Chief
Vendors: Zach Boxrud at Projectorpoint.com

We use a number of different ways to stack the projectors. The lenses of the projectors should be as closely together as possible and the projected images should be aligned as precisely as possible. The simplest way is to physically place the projectors on top of one another. One can use patented stereo alignment tools (doorstops) to easily align the projectors. One can also use standard stackers for slide projectors, such as the Chief ASU-2000. These stackers provide accurate positioning control and can be used conveniently on a table or cart. Reason and Projectorpoint.com have developed a stacker for the traveling Geowaller. It is a tabletop stacker with removable feet, and a removable custom filter holder. All of this fits in the Jelco Carrying case available from projectorpoint.com.

We have outfitted several classrooms with the projectors ceiling mounted stackers, such as the Chief_LCD2C double stacking ceiling mount.

Filter Holders

Projectorpoint.com now carries 4 different styles of filter holders.

Filter Rings  Holds the Hoya 72mm filters for the Infocus LP530s.

Goal Post Filter Holders  Will hang on a tiled ceiling in front of a stacked ceiling mounted projector system. This will allow you preserve the life of the filters.

Computers

The key part of a computer being used in a GeoWall is the graphics board. See our list of graphics boards that have been tested with the GeoWall. The computer could be any late model

Windows

Vendor: Reason Computers

The computer could be any late model Intel or AMD machine running Windows 2000 or Windows XP.

MacOSX

Macintoshes are a minority in the GeoWall world. See Andy Johnson's McGeoWall page for current configuration information. The McGeoWall has two requirements: OSX and one of the graphics boards from the tested graphics board list.

Linux

Both Red Hat and SuSE have been tested with most of the GeoWall software. Make sure that you have installed the latest drivers for you graphics boards.

List of Tested Graphics Boards

On the most general level the graphics card needs to have two monitor outputs to provide output to left and right projector. The most sophisticated Quadro4 cards produce a Quad Buffered Clone Mode that allows the standard OpenGL Stereo Mode to be supported in the GeoWall.

GeForce2 Twinview
GeForce4 Ti4400/Ti4600
Quadro4 550,700,750 or 900 XGL
The Quadros are the only boards that do Quad Buffered Clone Mode.

ATI cards that have two video outputs have been found to work but are not widely used in GeoWalls.

Stereo Cameras

Stereo photography with digital cameras is rapidly evolving, but and all-in-one digital stereo camera has yet to emerge. The links below describe a few options for putting together a digital stereo camera setup using off-the-shelf components.

• Dr. Monte Ramstad's most recent digital stereo camera setup
• University of Michigan's digital stereo camera page

Carrying Cases

Projectorpoint.com carries custom Jelco cases so you can take your Geowall on the road. These cases will hold the projectors, Reason shuttle PC, Keyboard, Mouse, Cables, Collapsible Stacker, and any other small accessories you may have. The only thing it won't carry is the screen.