A developer successfully ported software-only 3D graphics rendering logic, originally developed for an ATmega328P microcontroller, to the classic ZX Spectrum 48K+ using Z80 assembly language. This project involved significant optimization due to the Spectrum's limited resources. The initial C-based implementation achieved 6.2 frames per second (fps). By rewriting the core logic in highly optimized Z80 assembly, replacing costly divisions with multiplications using reciprocal lookup tables, the frame rate jumped to 14.0 fps. Further optimization in a separate branch involved pre-calculating paths and screen memory writes, resulting in a phenomenal 40 fps, though this required several minutes for the initial pre-computation. The resulting demo files, including a statue and a sphere model, are available for testing in emulators like FUSE using the z88dk cross-compiler toolchain.

Key Points:

- A developer ported 3D rendering logic from an ATmega328P to the ZX Spectrum 48K+ using Z80 assembly.

- Optimization techniques included replacing divisions with reciprocal lookups, boosting performance from 6.2 fps (C) to 14.0 fps (ASM).

- A pre-computation branch achieved 40 fps by calculating paths beforehand, albeit with a multi-minute setup time.

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