Great topic. The core insight most people miss is that rollback isn’t really about eliminating latency—it’s about hiding it behind prediction, and the architecture has to be deterministic to work. With a GGPO-style setup, you run each player’s machine N frames ahead (typically 2-6 frames depending on ping) using a rollback buffer, and every frame you compare the actual received input against your prediction. When they mismatch, you rewind the game state to that frame, adjust the buffer, re-simulate from that point, and render the corrected frames. The critical requirement is that your simulation must be fully deterministic—no floating-point randomness, no unseeded PRNG, no reads of system time mid-frame—otherwise the rollback will desync and you’ll get that ugly stutter jump that kills the feel. Input buffering is where most amateur implementations die; you need a clean separation between mobile inputs (queued, never sent raw) and the rollback frames, otherwise you leak input delay straight back into the game.
For real-world tuning, the sweet spot on rollback amount depends heavily on your round-trip time, and I’d argue the biggest practical win is using a “rollback on ping spike” detection loop rather than a static frame count.
You want to measure the actual delay between sending an input and receiving the opponent’s response, then dynamically expand the buffer when jitter creeps?
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