Participants of the interactive "Videoplace" system by Myron Krueger are identified by a real-time video camera. The image is analized as a "shadow" on the graphic screen. Each participant (shadowpeople) can now interact with objects provided by the computer system and other shadow people.

The "Videoplace" system perceives one or more participants and responds to their movements in realtime. Video cameras view participants standing in front of a backlighting assembly that makes it easy for the computer to distinguish their images from the background. The video image of the participants is reduced to a binary image which is analyzed by a series of hand-made specialized computers that can perform their algorithms thousands of times faster than a standard personal computer.

The "Videoplace" system identifies each participant's head, arms, legs, hands and fingers and determines their rate of movement, This analysis is performed on separate processors for each participant. Once each person's image is understood, it is analyzed with respect to the objects and creatures on the graphics screen. For instance, the computer maycheck to see whether a participant is touching a graphic object. Since the participant's image may be moved, scaled or rotated anywbere on the screen, the relationship of the transformed image to other objects on the screen must be considered.

Once each person's actions have been interpreted with respect to the graphic world, the computer must determine the consequences of these actions and initiate responses of its own. It then schedules its responses and directs subordinate processors dedicated to the generation of graphics, image transformation and sound to effect responses.

"Videoplace" is exhibited in two modes. In one, it selects a new interaction automatically when a person enters. It continues that interaction until all the participants have left the environment. When a new person enters, the next interaction in the sequence is triggered. In th second mode, the exhibit operates as a dialog between two participants: one who understands and controls the system and a second naive participant who is visiting the exhibit for the first time. The knowledgeable participant is seated at tbc "Videodesk" which operates in a manner similar to the "Videoplace" environment. The person at the desk can interact with the person in the "Videoplace" environment using the image of his or her hands. In addition, the "Videodesk" operator controls the selection of interactions from a menu. The person at the desk, a stand-in for an artificial intelligence system with a Vaudevillian sense of humor that will ad lib invent interactions on the fly, makes decisions that someday will be made by the computer.

Technical Background

Overall control of the system is asserted by a National 32016 processor running on a Multibus. "Videoplace" hardware runs on a specialized bus structure that allows great flexilbility in the intermingling of video images, standard graphics and the output of specialized graphics generators. Much of the programming is done in C, although each of the subordinate processors has a specialized architecture that is controlled by a unique microcode. The twelve specialized processors operate in parallel to the main processor. They are told what kind of processing to perform and do so automatically until their rules of behavior are changed. The sound is generated by two ATT WE32 digital signal processors, one of which performs Fourier synthesis and another which modulates the behavior of the sixteen channels of the first once a millisecond.