There are times when a project becomes such a big part of a maker’s life that they find themselves revisiting it even years later. [Thanassis] combined this phenomena with his love for the ZX Spectrum when he ported one of his old 3D rendering projects to the ZX Spectrum 48K. The video below shows the result, and they speak for themselves.
The roots of this project go back around three years, when [Thanassis] posted a similar project for the ATMega328 which employed fixed point math tricks for achieving the graphics. The code needed to be even tighter to run on the Spectrum, eventually getting boiled down to just a handful of calculations. This got the proof of concept working with the z88dk compiler, but it wasn’t quite fast enough.
In the end, hand assembly optimizations nearly doubled the performance to a blistering 10 frames per second. There’s also a version that kicks it all the way up to 40 FPS, but only if you give it a few minutes to do the calculations ahead of time. With a few teaks and the right display, this project could produce some very cool retro visuals.