@skidpad/replay

Deterministic replays and lightweight ghosts for @skidpad/core. A replay records inputs and keyframes and re-simulates bit for bit (seekable); a ghost records a pose track and plays back with no simulation.

import {
  ReplayRecorder,
  ReplayPlayer,
  createReplayWorld,
  encodeReplay,
  gzip,
} from "@skidpad/replay";

const rec = new ReplayRecorder(world, sp, { definitions: [def] });
rec.step(1 / 60); // instead of world.step
const bytes = await gzip(encodeReplay(rec.finish()));

const player = new ReplayPlayer(createReplayWorld(sp, replay), replay, {
  beforeStep: (step, world) => game.applyRules(world), // host-side logic
  onRestore: (step, state) => game.load(state), // on seeks
});
player.seek(60 * 30);

Per-wheel surfaces are recorded and re-applied. A replay is about 48 bytes per car per step plus keyframes before gzip.

Guide: replays and ghosts.

License: MIT OR Apache-2.0.