private float EvalForTwoKeys(FRichCurveKey key1, FRichCurveKey key2, float inTime)
{
var diff = key2.Time - key1.Time;
if (diff > 0f && key1.InterpMode != RCIM_Constant)
{
var alpha = (inTime - key1.Time) / diff;
var p0 = key1.Value;
var p3 = key2.Value;
if (key1.InterpMode == RCIM_Linear)
{
return(MathUtils.Lerp(p0, p3, alpha));
}
if (IsItNotWeighted(key1, key2))
{
const float oneThird = 1f / 3f;
var p1 = p0 + key1.LeaveTangent * diff * oneThird;
var p2 = p3 - key2.ArriveTangent * diff * oneThird;
return(BezierInterp(p0, p1, p2, p3, alpha));
}
// it's weighted
return(WeightedEvalForTwoKeys(key1, key2, inTime));
}
return(key1.Value);
}
private static bool IsItNotWeighted(FRichCurveKey key1, FRichCurveKey key2)
{
return(key1.TangentWeightMode is RCTWM_WeightedNone or RCTWM_WeightedArrive && key2.TangentWeightMode is RCTWM_WeightedNone or RCTWM_WeightedLeave);
}
private float WeightedEvalForTwoKeys(FRichCurveKey key1, FRichCurveKey key2, float inTime)
{
var diff = key2.Time - key1.Time;
var alpha = (inTime - key1.Time) / diff;
var p0 = key1.Value;
var p3 = key2.Value;
var oneThird = 1f / 3f;
var time1 = key1.Time;
var time2 = key2.Time;
var x = time2 - time1;
var angle = Math.Atan(key1.LeaveTangent);
var cosAngle = Math.Cos(angle);
var sinAngle = Math.Sin(angle);
double leaveWeight = key1.LeaveTangentWeight;
if (key1.TangentWeightMode is RCTWM_WeightedNone or RCTWM_WeightedArrive)
{
var leaveTangentNormalized = key1.LeaveTangent;
var y = leaveTangentNormalized * x;
leaveWeight = Math.Sqrt(x * x + y * y) * oneThird;
}
var key1TanX = cosAngle * leaveWeight + time1;
var key1TanY = sinAngle * leaveWeight + key1.Value;
angle = Math.Atan(key2.ArriveTangent);
cosAngle = Math.Cos(angle);
sinAngle = Math.Cos(angle);
double arriveWeight = key2.ArriveTangentWeight;
if (key2.TangentWeightMode is RCTWM_WeightedNone or RCTWM_WeightedLeave)
{
var arriveTangentNormalized = key2.ArriveTangent;
var y = arriveTangentNormalized * x;
arriveWeight = Math.Sqrt(x * x + y * y) * oneThird;
}
var key2TanX = -cosAngle * arriveWeight + time2;
var key2TanY = -sinAngle * arriveWeight + key2.Value;
// Normalize the time range
var rangeX = time2 - time1;
var dx1 = key1TanX - time1;
var dx2 = key2TanX - time1;
// Normalize values
var normalizedX1 = dx1 / rangeX;
var normalizedX2 = dx2 / rangeX;
var results = new double[3];
BezierToPower(0.0, normalizedX1, normalizedX2, 1.0, out double[] coeff);
coeff[0] -= alpha;
var numResults = CubicCurve2D.SolveCubic(ref coeff, ref results);
float newInterp;
if (numResults == 1)
{
newInterp = (float)results[0];
}
else
{
newInterp = float.MinValue;
foreach (var result in results)
{
if (result is >= 0.0f and <= 1.0f)
{
if (newInterp < 0.0f || result > newInterp)
{
newInterp = (float)result;
}
}
}
if (newInterp == float.MinValue)
{
newInterp = 0f;
}
}
var outVal = BezierInterp(p0, (float)key1TanY, (float)key2TanY, p3, newInterp);
return(outVal);
}