Isometric surface plotting on a Vectrex CRT using analog voltages

Stuff and Nonsense posts:

A while back I converted an old Vectrex vector CRT games console so that the display could be controlled directly by voltage signals from a modular synth (after being inspired by a demo I saw from Andrew Duff)

Since then I have occasionally thoughts about making synth modules that might work well with the setup and one idea was something to enable isometric “3D” surface plotting from the synth. Back in my school days I messed around with making little isometric 3D demo programs on the BBC Micro computers at school and remembered it being pretty easy to do.. Basically if you have “logical” x and y position and a z position which is some function of x and y, then you can plot on the screen as basically

Xscreen = (x – y)
Yscreen = (x + y + z)

with appropriate scaling and offsetting to place (0,0) at the bottom centre of the screen. The line x=y then runs vertically up the middle of the screen.

See more in the post and in the video above.