Early Graphics at Livermore

I think that Livermore’s first computer able to produce images was the IBM 704 computer which was equipped with the IBM 780 CRT display for direct viewing and the 740 film recorder with its own CRT. A program would put 10 bit x and y values in a word and execute an IO command that would cause that point to be plotted. The operation required 151 µsec. The CRT display had a slow phosphor and the point image would linger for a number of seconds on the display but the image was permanently captured on the film. By turning out the computer room lights substantial images could be seen on the display. The film recorder captured permanent images for better viewing however. A different IO command would cause the non-sprocketed film to advance one frame.

We requested a similar device for the LARC and it was delivered. We equipped the LARC with a sprocketed film magazine that was fast and precise. This allowed the production of black and white movies. An early production code on the LARC computed a general circulation weather model. Chuck Leith, of Livermore, wrote a general circulation program for the LARC and programmed the LARC to draw isobars. He gave a talk and showed his movies before a group of weather modelers. Someone in the audience remarked that the jet stream was plainly visible in the movies. It had been thought that more physics was needed to produce the jet stream. The other weather modelers soon acquired computer graphic output.

A commercial machine called the “Houston Fearless” would take a strip of film and “color mix” it onto color film. Every third frame of the input strip would be exposed thru a filter of the same color. Each color frame would be exposed to three of the input frames each thru a different color filter, producing color movies.

By all obvious accounting methods color movies were the cheapest way to extract information from the computer for human consumption. They complemented and partly displaced traditional printing numbers on reams of paper. Most movies were not color. There was an owl shift that would produce movies from over-night computer runs.

There were then U.S. government budget office restrictions on buying computer equipment. Those restrictions generally forbad such frivolous things as graphic output. Livermore had been buying computer equipment since before that office had been established and out politics was good enough that we could ignore those rules.

Our first computer from Digital Equipment Corporation was the PDP-1. It was an 18 bit computer and each PDP-1 came with a CRT. We programmed the PDP-1 to do a variety of image tasks. The PDP-1 had a light pen which was used for a number of early graphical input ideas. Some were used in production. See this for a great deal more information of Livermore’s use of the PDP-1.

A few years later Livermore acquired a machine from Stromberg Carlson which used a charactron to produce an image on a Xerographic drum which was then transferred to paper and then heated to fuse the ‘toner’. It handled text only for it could not stop the paper for complex images.

The CalComp plotter arrived at Livermore in the late 50’s. This produced 30 inch by many inch drawings with a drum upon which the paper was wrapped, and a pen. Both the drum and pen were moved by a stepping motor that took individual step instructions from a mag tape. The plotter was fairly slow (300 steps/sec; 100 steps per inch) but it was reliable and good for short turn-around jobs. It was also low cost and high accuracy.