The computer displays a live video feed from the camera, which is connected to one of the computer's two Firewire (IEEE 1394) ports. The computer processes the video signal in real time, to mask out a certain range of colors. (This greenscreen masking is adjustable in a calibration screen.) The computer's monitor signal is sent to the two plasma monitors, turned 90 degrees clockwise. Note that the live video signal is also flipped 180 degrees horizontally (strictly speaking, it is vertically, but since the monitors are turned it appears horizontal). This is done so that the monitor facing the user acts as a mirror -- if the user moves in one direction, they go the same direction on the monitor.

When the Poster software first starts up, it may display the previous poster image with a different background; this is fixed when a button is pressed. When the computer receives a button press, it displays the proper poster behind the masked video signal. The poster image contains an outline which the user(s) can use as a guide in positioning themselves. The computer begins counting down from 10 (the countdown time is also adjustable in the calibration screen). This is accompanied by audio cues, all of which come from the computer, to which a small amp and speaker are connected. At this time, the computer also begins blocking any further button presses.

At zero, the computer changes its masking. It puts up a background image of the poster without outlines (so they do not appear in the picture) and flips the image 180 degrees horizontally (as it appears on the screens). This is done to correct the mirror effect, so that anyone wearing a printed t-shirt will not have the lettering appear backward. The computer grabs a frame of the masked live video feed, and keeps it on the screen for 10 seconds (this time also adjustable in the calibration screen). The computer also tells the show controller to trigger the flash, just after the photo has been snapped, so that the light from the flash does not change greenscreen masking.

While the snapshot is being displayed, the computer saves a copy of it, as well as a smaller, thumbnail-sized copy, in the localimages folder. It then tries to copy the files over the network to the remote location specified in the calibration screen. If the remote computer is not mounted, it tries to mount it. (A spinning cursor appears when this is happening.) If it fails to copy the image on the first try, the computer will beep (sound of ringing glass). If it cannot mount the remote computer, it will write the name of the snapshot file to a text file called IMAGES_NOT_UPLOADED.

Each time the computer takes a snapshot, if the remote volume is not mounted it will try to mount it. When it finally does, if there are images listed in the IMAGES_NOT_UPLOADED file, it will try to copy a few of them along with the newly snapped image. So if the Gift Shop computer has been unavailable for a while while the poster is running, it will take some time for it to copy all of the images -- they will not all appear at once on the shop computer. Once an image has been copied to the remote computer, it is deleted from the Poster computer.

After the specified display time, and after it has tried to copy the image(s) to the remote computer, the computer returns to a live video feed, showing the last selected poster (with people outlines) in the background. It tells the show controller to darken all of the buttons, and it waits for a button press.

The calibration screen is activated by pressing the spacebar on the keyboard (inside the crate on the floor). IMPORTANT: The computer takes a reference snapshot when the calibration screen is activated, so nothing should be in front of the greenscreen. There are four basic steps to adjust masking:

Step 1: First, a reference frame is taken. This is done automatically upon activation of the calibration screen, but one can be taken manually with the button in Step 1.

Step 2 is choosing a color that will be used for masking. First, make sure that the Remove Background button in Step 3 is unchecked. Click the Step 2 button that says Choose Color. It will change to say Click on a Color. Click somewhere in the middle of the video frame, until the button changes back to say Choose Color.

Then adjust the tolerance slider beneath the button. A value of around 99 usually works best. Adjust the tolerance so that most of the green disappears. At this point, it is helpful to stand in front of the greenscreen, or have someone else stand there while adjusting. Or you can stick your hand in front of the camera, or get up in front of the screen yourself, then go back and adjust as needed.

The set of three numbers beneath the slider represent RGB color values; the center one is green and should be the largest number. These are mainly provided for reference, but numbers can be manually input here.

Step 3: Now activate the Remove Background button, and all of the green should disappear. This compares the incoming video (30 times a second) to the reference frame, and makes invisible anything that is the same. The tolerance slider is best left to about 30, but can be adjusted as needed.

If the video feed is not clear: First, try unplugging and re-plugging the Firewire cable going into the computer, then reboot (press ESC to exit the Poster program, click at the top of the screen to activate the menu and select Restart from the Special menu).

Error Messages: The computer has a Control Panel called Okey Dokey which says OK to any dialog box that appears on the screen. If an error keeps flashing on the screen, that means that each time Okey Dokey is dismissing it but the error persists. In this case, try pressing the ESC key repeatedly, or holding the Apple (Command) key and pressing the period key repeatedly.

If the message is a Script Error: please make a note of it and email to kevin@woed.com. Pressing OK to one of these errors will attempt to keep running the program. But if the error prevents continued running it will keep appearing, in which case the error must be cancelled (using the ESC or Cmd-. keys) and the program stopped. Then reboot.

If the message is a communication error between the computer and printer: first try rebooting. If that does not work, check the printer power and data cables. On the computer's desktop, go to the Chooser from the Apple (far left) menu, select POSjet, and verify that a USB connection appears in the right-side window.

If images are not appearing on the Gift Shop computer, first check the Poster computer. Exit the Poster software (by pressing the ESC key; you may need to click the mouse first). Once on the desktop, see if the volume printstation appears on the desktop.

If not, look in the Poster036b folder. Double-click on the file called mountvolume.applet. If nothing happens for a while and there is a spinning cursor, it probably means that Poster cannot see Print Station on the network.

Go to the Apple Menu/Chooser (click at the top of the screen to activate the menubar), and click on Appletalk. If printstation appears in the right-hand window, run the mountvolume.applet again to mount it. If this does not mount the Print Station, then the login information on Print Station may have changed. This information is set in the File Sharing control panel of Print Station.

If login information has changed, it will need to be changed on the Poster computer as well. Open mountvolume.source on Poster, and enter the new information there. Then choose Save from the File menu, then Save As Run Only, and save as a Classic Applet, with the box that says Never Show Startup Screen checked and the Stay Open box unchecked. Save it as mountvolume.applet, replacing the existing file.

If the Print Station does not mount, and does not appear in the Chooser, verify that Poster has network connectivity by opening Internet Explorer (inside Poster/Applications (OS9) or under the Apple menu under Recent Applications. If it does not connect to anywhere, check the Ethernet cable going into the computer. Call IT Partners if necessary.

If the Poster computer has network connectivity but still does not see Print Station, go to the Gift Shop and verify that Print Station is on and the Ethernet cable is connected. Check its network connectivity and File Sharing settings as above.

The machine originally specified for this exhibit was a 933MHz G4 with a fast SCSI-2 drive. However, when a power surge destroyed the Bronc computer, the Poster computer moved there, and the 733MHz/IDE G4 formerly for R04 Ranch Women replaced the Poster computer. A faster processor would probably boost its video processing capabilities, but it was deemed adequate for the task. This particular model has 128MB RAM and a Nvidia GeForce2 MX graphics card.

More information on the G4 is available here.

Stealth Serial Port driver is here.

More information on the CMP307XU is available here.

Data: An Ethernet cable comes in from the floor to the computer. The printer is directly connected by USB with a cable run from the crate, under the floor, to the printer. A keyboard is plugged into the other USB port, with a mouse plugged into one of the two USB ports on the keyboard. The camera is directly connected with a Firewire cable which runs from the side of the camera (bottom as it is mounted), down through the floor, and up into the crate. The show controller is directly connected to the serial port on the computer, with all cables inside the crate.

The large flourescent fixtures on the side of the greenscreen contain greenscreen-compliant Kino-Flo flourescent tubes. The fixtures were pulled away from the screen to provide a more even spread. There is an additional flourescent fixture above the screen, with standard flourescent tubes. Various track lights were aimed to attempt to fill shadows and darker areas.

In the Poster program, printing layout is controlled by a file called "barcodeprinting.cst," in the Poster036b folder on the desktop. (Download it here.) To re-install the Dymo Labelwriter, use this barcodeprinting.cst file.

After heavy use, the Dymo LabelWriter 330 Turbo was deemed unsuitable for this application, due to difficulties with paper spooling and tearing, heat buildup, and communication problems with the computer.