Everything There Is To Say In Explaining How Computer Graphics Work


This office has received a number of letters asking it to explain computer graphics. “What about computer graphics,” they’ll say. “Explain yourself, if you are a computer graphics. If you are not a computer graphics, then why or why not?” It’s a bit stressful. I had thought we were to take a multiple choice question. “But,” reads one follow-up letter, “an essay answer is a multiple choice; there are just a Borgesian infinitude of possible answers.” Who among us would dispute this charge?

The first images produced by computers were by our standards low-resolution affairs. The earliest known images used the technologies of old-time radio, or as they knew it in the old times, “time radio”. In this the computer would just describe what the image should be, trusting to the “theatre of the mind” to fill in the details. “It’s a calendar for February 1949, but with Snoopy beside it,” would come the voice from the warm glowing hearth of a Harvard Mk II. The listener could fill in all the perfect little details of which days of the week were in February, and which Februaries were in 1949, and what this Snoopy fellow was all about. It extended naturally to more serious applications. “Here’s a wireframe cube rotating as if it were three-dimensional,” UNIVAC famously reported on Election Night, 1952. It was so plausible that critics came to ask whether the demonstration was rigged. It was not, precisely, but UNIVAC was warned ahead of time that the topic of shapes in dimensions would come up.

The first digital images were formed by taking photographs of the pointer fingers of the lead programmers and aiming them in different directions. This finger was chosen for the ease of indexing. It was a great format for pictures of fingers. It was also decent, if you had a big enough screen, to make for pictures of strange-colored grasses. Maybe the fur of some animal that had a lot of jointed fur with the occasional fingernail. So resolution was a bit of a problem.

Everyone understood this to be a transitional phase, just something to prove out the technology that would let them use numbers instead. Well, everybody but Ray, but you know what he’s like. Which numbers were a great debate. 1 was an obvious choice, since it already looked so much like a finger. It would need almost no new code worth mentioning, especially if you used a font that was easy on the serifs. The other number, though? That took a lot of fighting. 0 seems, today, to be the obvious choice. But a good argument was made for -1, on the grounds that then they could keep using fingers for both the 1 and the – sign. The dispute continued until a standard was finally agreed to, last year, in which everyone uses a 3 and a 4. The argument took some weird turns. Vestiges of the old system remain in how computer systems do not speak exactly of a three, but rather of a “quarter-dozen”, or “quatre-vingt” as they say in French, incorrectly.

A fascinating variation developed in the 1960s when research indicated there were maybe six things we needed a computer to show anyway. So why not set up a computer with a filmstrip containing six or, for deluxe systems, seven images, and simply have it show whatever seemed most relevant? People were indeed happy with this, especially if they got to work the projector, and doubly so if they were allowed to make a “beep” noise whenever it was time to move to the next slide. These slides were: Abraham Lincoln, a brontosaurus, a Mercator projection map of the world, a diagram of the heart, Snoopy, the Pioneer 4 space probe, and in the deluxe system, Times Square.

This is still at heart how computer images work. A modern computer image is a gathering of millions of colors, represented. Admittedly, some of the colors get reused. But to keep all these sorted out and in the right locations we have to simplify some. A classic organization or “compression” scheme is to break the original image up into millions of pieces, then individually wrap each piece in a protective medium, and then forget where they were. This is known as a “lossy” image format. When called on to show the image, the computer panics and puts together what it can using the same original seven base images, plus — since 1989 — that picture of astronaut Bruce McCandless spacewalking using his cool rocket backpack. There are also “lossless” image formats, but these are annoying to use because every time you do beat them in a game they insist that it was best-three-of-five, or best-four-of-seven, or best five-of-nine, and on and on until you give up.

Further questions to this office may be sent in care of this office at this address. Thank you.

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Author: Joseph Nebus

I was born 198 years to the day after Johnny Appleseed. The differences between us do not end there. He/him.

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