I’m fascinated by things that are, to be fair, quite dull. Usually, these things are related to old-school computing or lack of it. I’m intrigued by ingenuity of people who had to solve problems that simply don’t exist today. Here’s an example.

Turn away now if you are in any way cool. You won’t be after you’ve read this.

These days, you can create anything you like on a desktop PC with a 3d graphics package. Back in the indistinct period of time known as “the day”, it wasn’t so easy. Various tricks had to be used, be it miniatures or combining simple computer generated effects to give the illusion of something much more complex than it was.

The BBC, during continuity announcements, used one of these before 1985:

It’s a camera that points at various panels that hold mechanical versions of the BBC world (top left of the picture), the clock, various “techinical difficulties” captions (bottom) and the school’s programmes countdown clock. You may remember that one if you went to school at any point in the 80s.

Here’s another look at the mechanical globe.

It had mirrors and lights around it meaning that after a bit of video colouring it came out looking like this:

In 1985, a computer generated title card was created to replace this. How, in 1985, did they created such a smooth, antialiased bit of CG when my BBC Micro outputted pixels the size of a baby’s fist. Was this really a fully rendered, shaded and textured globe?

Nope.

Here it is:

For anyone too young to remember, the globe spun.

The images is made up of three components. The sea is a single shaded circle, and the land is another shaded circle, both drawn on a Quantel system. Data is then read from a rack of EEPROM chips for each frame, telling the video hardware which bits of the gold globe to render, and which bits of the blue globe to not render. This means that only two full colour frames are stored (the “BBC1” text was part of the blue globe’s frame) and the rest is smaller chunks of data read in for each frame. There was data for 600 frames. Some compression was used, meaning the two full frames were 600KB each, and each frame of land mass data was just 7KB. All this was placed into a single metal box with a switch. The switch triggered the “SUBTITLES 888” text to appear under the “BBC1” text. The BBC also had to produce versions of these boxes for each region, so that on regional programs, the correct regional identifier appeared beneath “BBC1” (ie “Northern Ireland”, “East Midlands”.

In all, 6000 EEPROM chips had to be sourced and filled with data, for which the BBC used a VAX-11.

There’s a few more pictures of the hardware, some test output and links to some further, more technical reading here.