Fable-5.1 rewrites Trackmania physics engine in pure C, ~2400x/core faster

adonis_singh · x · 2026-09-02

A developer had Fable-5.1 fully rewrite the Trackmania Nations Forever physics engine in pure C, taking about a day.

Performance: 2400x faster per core in realtime (for a full RL step); batched over 28 CPU cores it reaches 1.2M+ steps/s — measured during a heavy training run so it's a floor, with 1.9M/s expected on a clean machine. The demo video recreates the game with its assets rendered in a browser, driven by a small PPO policy trained for only 20 minutes.

Related event: Fable-5.1 Rewrites TrackMania Physics Engine in Pure C in a Day(2 posts)→

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