How Scanimation Was Done

Analog Computing

The Scanimate is basically an analog computer connected to a scan converter. This means that high-contrast artwork is placed onto a light table under a "high rez" camera. In the late seventies, that meant it was about a 500 line vidicon camera, but was not interlaced video, for reasons I'll get into below.

The image then appeared on a "high rez" CRT, (cathode ray tube) which in turn was scanned by a regular monochrome NTSC video camera. The reason for this "re-scanning" is that the analog computer could do all sorts of wierd and wonderful things to the sweep on the CRT, thus animating the artwork. The only trick was that the "animator" actually had to "program" the move by wiring up a complex analog circuit and adjusting any (and sometimes all) of about 250 knobs. The wiring was done at several "patch panels" where you had access to the innards of the analog "CPU" waveforms. You had horizontal and vertical sawtooth waveforms, a variety of oscillators which could phase lock to the horizontal or vertical sweep or each other, and summing amps and multipliers. Ramp generators could be fired off in sync with a specific timecode on videotape, and each ramp could "multiply on" an oscillator, offset, or whatever you needed to wire up to "bend" the raster to the client's content.

The original raster could be "sectioned" so that if the artwork had up to five words, the words could be individually animated. The second camera's output (the one viewing the CRT) was colorized according to the greyscale values it saw, and that image could then be layered by keying it over videotape of previous "passes". The passes were recorded on 2" IVC helical analog video recorders, which could (sometimes) manage an embarrasing number of generations before the client noticed it. You could never get away with it when you needed to.

The client(s) would sit on couches at the rear of the room, and at least at Image West, there were two Scanimates, one on either side of the room. A video switcher and monitors were at the front of the room, and through a door were the video tape machines, which were 2,000 pound monsters that ran on megawatts of power and required compressed air.

Because the Scanimates produced output in "real-time", the clients could literally sit down and say things like "Make it move a little faster", or "Can you make it more of a teal color?", and the animators would tweak it, get an approval, tape it, and the guy would walk out with his master. It was hundreds of times faster than cel animation, and so $2,500/hour to command the entire facility was a bargain. If the client wanted something more complex, of course it took longer, and cost more. If he couldn't make up his mind, we could keep trying this and that, and he paid for his own indecision.

But as wonderful as it sounds, it was a real pig! Animators that know about form, composition, design, motion, and all those asthetic concerns are usually not analog circuit engineers too! And, analog circuit designers don't tend to have the training to know what's ugly and what's not! Animators would tend to be "in training" for years, until they'd look around and figure out that they had been doing it longer than anyone else.

There are many legends in Scanimate Lore, and hopefully I can get some of the Scanimate alumni to mail me some of them so I can share them here.

Scanimate was put out to pasture by the new digital technology. With digital computers and frame buffers and digital video recorders, animators could literally do anything the client could imagine. But only recently has the digital technology gotten fast enough to allow the kind of "real-time" interactivity that these old engines took for granted.

Here is an mpeg movie (3.4M) of Scanimate in Action circa 1981. You will see all of the above as it was.

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