Class AnimationTrack<T>

A typed keyframe sequence over clip-local time (§17).

const track = new AnimationTrack({
  path: "transform.position",
  adapter: vector3Adapter,
  times: [0, 0.5, 1],                      // seconds (§7a)
  values: [new Vector3(0, 0, 0), new Vector3(0, 2, 0), new Vector3(0, 0, 0)],
  interpolation: "cubic",
});
track.sample(0.25, out);                   // → out, mutated
Copy

Sampling outside the key range

Clamped, not extrapolated: below the first key the first value is returned, at or above the last key the last one. This differs from §13's trajectories, which extrapolate their closed forms, and the difference is deliberate — a trajectory is a curve that happens to be parameterized by time, while a clip track is authored content with a beginning and an end. Repeating, ping-ponging, and holding past the end are the player's decisions (WP-4.6), made by transforming the time it passes in; a track that extrapolated would fight every one of them.

Sampling time must be finite: nothing is validated on the sample path (it is per-frame, per-track code), so a non-finite time propagates into the result rather than throwing.

Overshoot

"cubic" and "hermite" can leave the interval spanned by their keyframes — that is what makes them useful for anticipation and follow-through — and nothing here clamps them back. A track whose values must stay in range uses "linear" or "step".