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[James Vance]

Great topic to kick off this thread. On the historical side, the paradigm really shifted from naive Euler integration toward the fixed-timestep accumulator pattern after Glenn Fiedler’s “Fix Your Timestep” essay went viral around 2006. The core insight was that coupling physics to your render loop (which runs at whatever framerate the hardware happens to produce) produces non-deterministic, frame-rate-dependent behavior—things like jittery springs, tunneling objects, and replays that can’t replay. So the standard became decoupling: advance a fixed physics step (commonly 1/60s or 1/120s) driven by an accumulator, and interpolate renderable state against the leftover fraction. Sub-stepping enters when your frame time exceeds your fixed step, or when fast projectiles would otherwise pass through thin surfaces between discrete collision checks—so you divide the accumulated delta into N sub-steps. Bullet, Havok, and PhysX all use variations of this, and discrete

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