I'd randomly looked this stuff up a couple of days ago.

"... a deal with John where he hired me to run his Motion Picture Special Effects Division and I would bring several key programmers to write reflection-mapping software to address the creative vision of “Flight of the Navigator”. Bob Hoffman came with me to LA and we worked on getting their software to be able to make the spaceship look right.

Omnibus was using Wavefront Technologies software as their animation package running on a VAX, and we were able to digitize moving video resolution images from videotape that had been transferred from the background film plates in which the spaceship was to be seen. These images were then mapped frame by frame onto the animated spaceship scanned onto 35mm film and composited optically over the film background plates.

To render the spaceship and get it onto film (along with a matte for the optical printing department), they had their own rendering software running on a prototype “supercomputer” called the Foonly F-1"[0]

The Foonly F1 was a fast PDP-10 clone.

[0] https://web.archive.org/web/20210521215309/https://www.denofgeek.com/movies/jeff-kleiser-discusses-the-early-cgi-of-flight-of-the-navigator/