intervalChanged method

Implementation

@override
void intervalChanged(int v1, int v2, int v3) {
  List<num?> pp = parameterPositions;
  int iPrev = v1 - 2;
  int iNext = v1 + 1;
  num? tPrev = pp[iPrev];
  num? tNext = pp[iNext];

  if (tPrev == null) {
    switch (getSettings()['endingStart']) {
      case ZeroSlopeEnding:

        // f'(t0) = 0
        iPrev = v1;
        tPrev = 2 * v2 - v3;

        break;

      case WrapAroundEnding:

        // use the other end of the curve
        iPrev = pp.length - 2;
        tPrev = v2 + pp[iPrev]! - pp[iPrev + 1]!;

        break;

      default: // ZeroCurvatureEnding

        // f''(t0) = 0 a.k.a. Natural Spline
        iPrev = v1;
        tPrev = v3;
    }
  }

  if (tNext == null) {
    switch (getSettings()['endingEnd']) {
      case ZeroSlopeEnding:

        // f'(tN) = 0
        iNext = v1;
        tNext = 2 * v3 - v2;

        break;

      case WrapAroundEnding:

        // use the other end of the curve
        iNext = 1;
        tNext = v3 + pp[1]! - pp[0]!;

        break;

      default: // ZeroCurvatureEnding

        // f''(tN) = 0, a.k.a. Natural Spline
        iNext = v1 - 1;
        tNext = v2;
    }
  }

  final halfDt = (v3 - v2) * 0.5, stride = valueSize;

  _weightPrev = halfDt / (v2 - tPrev);
  _weightNext = halfDt / (tNext - v3);
  _offsetPrev = iPrev * stride;
  _offsetNext = iNext * stride;
}