public Vector2 GetPosition(float time)
{
Vector2 temp;
if (ControlPoints.Count < 2)
{
throw new Exception("You need at least 2 control points to calculate a position.");
}
if (Closed)
{
Add(ControlPoints[0]);
_deltaT = 1f / (ControlPoints.Count - 1);
var p = (int)(time / _deltaT);
// use a circular indexing system
var p0 = p - 1;
if (p0 < 0)
{
p0 = p0 + (ControlPoints.Count - 1);
}
else if (p0 >= ControlPoints.Count - 1)
{
p0 = p0 - (ControlPoints.Count - 1);
}
var p1 = p;
if (p1 < 0)
{
p1 = p1 + (ControlPoints.Count - 1);
}
else if (p1 >= ControlPoints.Count - 1)
{
p1 = p1 - (ControlPoints.Count - 1);
}
var p2 = p + 1;
if (p2 < 0)
{
p2 = p2 + (ControlPoints.Count - 1);
}
else if (p2 >= ControlPoints.Count - 1)
{
p2 = p2 - (ControlPoints.Count - 1);
}
var p3 = p + 2;
if (p3 < 0)
{
p3 = p3 + (ControlPoints.Count - 1);
}
else if (p3 >= ControlPoints.Count - 1)
{
p3 = p3 - (ControlPoints.Count - 1);
}
// relative time
var lt = (time - _deltaT * p) / _deltaT;
temp = VectorUtils.CatmullRom(ControlPoints[p0], ControlPoints[p1], ControlPoints[p2],
ControlPoints[p3], lt);
RemoveAt(ControlPoints.Count - 1);
}
else
{
var p = (int)(time / _deltaT);
//
var p0 = p - 1;
if (p0 < 0)
{
p0 = 0;
}
else if (p0 >= ControlPoints.Count - 1)
{
p0 = ControlPoints.Count - 1;
}
var p1 = p;
if (p1 < 0)
{
p1 = 0;
}
else if (p1 >= ControlPoints.Count - 1)
{
p1 = ControlPoints.Count - 1;
}
var p2 = p + 1;
if (p2 < 0)
{
p2 = 0;
}
else if (p2 >= ControlPoints.Count - 1)
{
p2 = ControlPoints.Count - 1;
}
var p3 = p + 2;
if (p3 < 0)
{
p3 = 0;
}
else if (p3 >= ControlPoints.Count - 1)
{
p3 = ControlPoints.Count - 1;
}
// relative time
var lt = (time - _deltaT * p) / _deltaT;
temp = VectorUtils.CatmullRom(ControlPoints[p0], ControlPoints[p1], ControlPoints[p2],
ControlPoints[p3], lt);
}
return(temp);
}