special effects in the first three Star Wars movies (1977 to 1983).
Not sure which special effects you refer to, but the animations in the original movie, especially the ones during the briefing scene before the attack on the Death Star, were prepared on a PDP-11 using a Vector General 3D terminal and programmed using the GRASS language.
The VG terminals had a series of lamps that could be turned on or off using command strings. They removed one of these lamps and connected its wires to the shutter release of a stop-motion camera. The system would render one image on the terminal, which had its own "frame buffer" for the vectors, and then trigger the camera.
You will note there are two sorts of animations during this scene. One shows a distant view of the DS which then rotates and zooms. This is done entirely in the VG hardware, which did the math internally using its own math processor. So these could be quickly filmed by sending "rotate 1 degree Z, turn on lamp".
The ones where you are flying down the trench require new scenery to be drawn, which you can see "popping" into view. Between the appearances the existing items were individually zoomed to provide the illusion of motion, which you could get away with for a few frames before the perspective started to get wonky. So this section took an overnight run to film.
I tracked down the actual machine a few years ago. At the time it was in a warehouse outside Chicago. I contacted the Computer History Museum to see if they could get it - it still runs the graphics BTW! - but have not followed up.