lerp method

@override T lerp(double t)

Returns a lerped value based on theta.

Implementation

@override
T lerp(double t) {
  if (t <= 0.0) {
    return _values.first.value;
  }
  if (t >= 1.0) {
    return _values.last.value;
  }

  if (_pair == null ||
      _pair!.b.percent < t * 100.0 ||
      _pair!.a.percent > t * 100.0) {
    _pair = fetchFromTo(t);
  }

  if (t * 100.0 <= _pair!.a.percent) {
    return _pair!.a.value;
  }
  if (t * 100.0 >= _pair!.b.percent) {
    return _pair!.b.value;
  }

  final n = _pair!.a.curve.transform(
      (t * 100.0 - _pair!.a.percent) / (_pair!.b.percent - _pair!.a.percent));

  if (T == Matrix4) {
    final Vector3 beginTranslation = Vector3.zero();
    final Vector3 endTranslation = Vector3.zero();
    final Quaternion beginRotation = Quaternion.identity();
    final Quaternion endRotation = Quaternion.identity();
    final Vector3 beginScale = Vector3.zero();
    final Vector3 endScale = Vector3.zero();

    _pair!.a.value.decompose(beginTranslation, beginRotation, beginScale);
    _pair!.b.value.decompose(endTranslation, endRotation, endScale);

    final Vector3 lerpTranslation =
        beginTranslation * (1.0 - n) + endTranslation * n;
    final Quaternion lerpRotation =
        qlerp(beginRotation, endRotation, n).normalized();
    final Vector3 lerpScale = beginScale * (1.0 - n) + endScale * n;

    return Matrix4.compose(lerpTranslation, lerpRotation, lerpScale) as T;
  }

  if (T == int) {
    return (_pair!.a.value + n * (_pair!.b.value - _pair!.a.value)).round();
  }

  if (T == Color) {
    return Color.lerp(_pair!.a.value as Color, _pair!.b.value as Color, n)
        as T;
  }

  if (T == Offset) {
    return Offset.lerp(_pair!.a.value as Offset, _pair!.b.value as Offset, n)
        as T;
  }

  if (T == Size) {
    return Size.lerp(_pair!.a.value as Size, _pair!.b.value as Size, n) as T;
  }

  if (T == Rect) {
    return Rect.lerp(_pair!.a.value as Rect, _pair!.b.value as Rect, n) as T;
  }

  return _pair!.a.value + n * (_pair!.b.value - _pair!.a.value) as T;
}