interpolate method

dynamic interpolate(int i1, num t0, num t, num t1,)

Implementation

interpolate(i1, t0, t, t1) {
  var result = this.resultBuffer;
  var values = this.sampleValues;
  var stride = this.valueSize;

  var stride2 = stride * 2;
  var stride3 = stride * 3;

  var td = t1 - t0;

  var p = (t - t0) / td;
  var pp = p * p;
  var ppp = pp * p;

  var offset1 = i1 * stride3;
  var offset0 = offset1 - stride3;

  var s2 = -2 * ppp + 3 * pp;
  var s3 = ppp - pp;
  var s0 = 1 - s2;
  var s1 = s3 - pp + p;

  // Layout of keyframe output values for CUBICSPLINE animations:
  //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
  for (var i = 0; i < stride; i++) {
    var p0 = values[offset0 + i + stride]; // splineVertex_k
    var m0 =
        values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
    var p1 = values[offset1 + i + stride]; // splineVertex_k+1
    var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

    result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;
  }

  return result;
}