blendAt method

ClipBlend blendAt(Duration t)

The blocks' answer at t. Inside one block, that block. Inside two, the earlier leads and the later comes in, blend running 0 to 1 from the later's start to the earlier's end. Between blocks the last one to end holds its end; before the first, the first holds its start.

Implementation

ClipBlend blendAt(Duration t) {
  var active = [
    for (var c in clips)
      if (t >= c.at && t <= c.end) c,
  ];
  if (active.isEmpty) {
    MotionClip? before;
    for (var c in clips) {
      if (c.end < t && (before == null || c.end > before.end)) before = c;
    }
    var hold = before ?? clips.first;
    return (
      clip: hold.clip,
      time: hold.timeAt(before == null ? hold.at : hold.end),
      clip2: '',
      time2: 0,
      blend: 0,
    );
  }
  var a = active.first;
  if (active.length == 1) {
    return (clip: a.clip, time: a.timeAt(t), clip2: '', time2: 0, blend: 0);
  }
  var b = active[1];
  var overlap = (a.end - b.at).inMicroseconds;
  var blend = overlap <= 0
      ? 1.0
      : ((t - b.at).inMicroseconds / overlap).clamp(0.0, 1.0);
  return (
    clip: a.clip,
    time: a.timeAt(t),
    clip2: b.clip,
    time2: b.timeAt(t),
    blend: blend,
  );
}