/// <summary>
/// Evaluates the value at a position of this <see cref="Curve"/>.
/// </summary>
/// <param name="keys">Curve keys</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the value at the position on this <see cref="Curve"/>.</returns>
private static float EvaluateOscillate(CurveKeyCollection keys, float position)
{
var first = keys[0];
var last = keys[keys.Count - 1];
if (position != first.Position)
{
//go back on curve from end and target start
// start-> end / end -> start
int cycle = GetNumberOfCycle(first, last, position);
float virtualPos;
if (0 == cycle % 2f)
{
//if pair
virtualPos = position - (cycle * (last.Position - first.Position));
}
else
{
virtualPos = last.Position - position + first.Position + (cycle * (last.Position - first.Position));
}
return(GetCurvePosition(keys, virtualPos));
}
//in curve
return(GetCurvePosition(keys, position));
}
/// <summary>
/// Gets the curve position
/// </summary>
/// <param name="keys">Key collection</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the curve position</returns>
private static float GetCurvePosition(CurveKeyCollection keys, float position)
{
//only for position in curve
CurveKey prev = keys[0];
CurveKey next;
for (int i = 1; i < keys.Count; ++i)
{
next = keys[i];
if (next.Position >= position)
{
if (prev.Continuity == CurveContinuity.Step)
{
if (position >= 1f)
{
return(next.Value);
}
return(prev.Value);
}
//http://en.wikipedia.org/wiki/Cubic_Hermite_spline
//P(t) = (2*t^3 - 3t^2 + 1)*P0 + (t^3 - 2t^2 + t)m0 + (-2t^3 + 3t^2)P1 + (t^3-t^2)m1
//with P0.value = prev.value , m0 = prev.tangentOut, P1= next.value, m1 = next.TangentIn
float t = (position - prev.Position) / (next.Position - prev.Position);//to have t in [0,1]
float ts = t * t;
float tss = ts * t;
return((2 * tss - 3 * ts + 1f) * prev.Value + (tss - 2 * ts + t) * prev.TangentOut + (3 * ts - 2 * tss) * next.Value + (tss - ts) * next.TangentIn);
}
prev = next;
}
return(0f);
}
/// <summary>
/// Evaluates the value at a position of this <see cref="Curve"/>.
/// </summary>
/// <param name="keys">Curve keys</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the value at the position on this <see cref="Curve"/>.</returns>
private static float EvaluateCycleOffset(CurveKeyCollection keys, float position)
{
var first = keys[0];
var last = keys[keys.Count - 1];
if (position != first.Position)
{
//make the curve continue (with no step) so must up the curve each cycle of delta(value)
int cycle = GetNumberOfCycle(first, last, position);
float virtualPos = position - (cycle * (last.Position - first.Position));
return(GetCurvePosition(keys, virtualPos) + cycle * (last.Value - first.Value));
}
//in curve
return(GetCurvePosition(keys, position));
}
/// <summary>
/// Evaluates the value at a position of this <see cref="Curve"/>.
/// </summary>
/// <param name="keys">Curve keys</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the value at the position on this <see cref="Curve"/>.</returns>
private static float EvaluateCycle(CurveKeyCollection keys, float position)
{
var first = keys[0];
var last = keys[keys.Count - 1];
if (position != first.Position)
{
//start -> end / start -> end
int cycle = GetNumberOfCycle(first, last, position);
float virtualPos = position - (cycle * (last.Position - first.Position));
return(GetCurvePosition(keys, virtualPos));
}
//in curve
return(GetCurvePosition(keys, position));
}
/// <summary>
/// Evaluates the value at a position of this <see cref="Curve"/>.
/// </summary>
/// <param name="keys">Curve keys</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the value at the position on this <see cref="Curve"/>.</returns>
private static float EvaluateLinear(CurveKeyCollection keys, float position)
{
var first = keys[0];
var last = keys[keys.Count - 1];
if (position < first.Position)
{
// linear y = a*x +b with a tangeant of last point
return(first.Value - first.TangentIn * (first.Position - position));
}
else if (position > last.Position)
{
// linear y = a*x +b with a tangeant of last point
return(last.Value + first.TangentOut * (position - last.Position));
}
return(GetCurvePosition(keys, position));
}
/// <summary>
/// Evaluates the value at a position of this <see cref="Curve"/>.
/// </summary>
/// <param name="keys">Curve keys</param>
/// <param name="position">Position to test</param>
/// <returns>Returns the value at the position on this <see cref="Curve"/>.</returns>
private static float EvaluateConstant(CurveKeyCollection keys, float position)
{
var first = keys[0];
var last = keys[keys.Count - 1];
if (position < first.Position)
{
//constant
return(first.Value);
}
else if (position > last.Position)
{
//constant
return(last.Value);
}
return(GetCurvePosition(keys, position));
}
