Josef Svoboda’s Polyecran was a very fascinating audio-visual experience which was presented during the Expo 1967 in Montreal. One entered a large room and sat on the carpeted floor where you watched a wall of 112 cubes whose ever shifting and changing images moved backwards and forwards. Inside each cube were two Kodak Carousel slide projectors which projected still photos onto the front of the cubes. In all there were 15,000 slides in the 11 minute show. Since each cube could slide into three separate positions within a two foot range, they gave the effect of a flat surface turning into a three-dimensional surface and back again. It was completely controlled by 240 miles of memory circuitry which was encoded onto a filmstrip with 756,000 separate instructions. Viewers watched a wall of 112 projected cubes while seated on the floor. The show was about The Creation of the World of Man. On the 112 part screen, the earth came awake, flowers bloomed, tigers suddenly appeared, the first men walked the earth, then machinery was invented. Sometimes the image sequences would first appear complete, then be broken up abstractly in a modern art composition. It was pure multi-visual technique that enchanted the viewer. (Source: Michael Bielicky, «Prague–A Place of Illusionists, » in Jeffrey Shaw/Peter Weibel (eds), Future Cinema. The Cinematic Imaginary after Film, exhib. Cat., The MIT Press, Cambridge, MA/London, 2003, p. 99.)
The Diapolyecran was not an environment, strictly speaking. It was restricted to one wall and the audience sat on the floor or stood watching the 14/2-minute show. Only slide projectors were used. According to the "Brief Description":
The Diapolyecran is technical equipment which enables a simultaneous projection of slides on a mosaic projection screen consisting of 112 projec- tion surfaces. The surfaces are projected on from behind and they may be shifted singly, in groups, or all at once. This enables one to obtain with still images pictures of motion, and the picture groups thus obtained are best characterized as "mosaic projection."
Each of 112 slide projectors was mounted on a steel frame that had three positions: back, middle, forward. The images could be thrust out toward the audience or moved back from it. The mosaic was achieved by complex programming-there were 5,300,000 bits of information memorized on tape; 19,600 impulses were emitted per second. 
- Svatopluk Malý, Vznik, rozvoj a ústup multivizuálních programů, Akademie múzických umění, Prague, 2010. (Czech) review