/// <summary>
/// Gets the parameter along the polyline which is closest to a test-point.
/// </summary>
/// <param name="testPoint">Point to approximate.</param>
/// <returns>The parameter along the polyline closest to testPoint.</returns>
public double ClosestParameter(Point3d testPoint)
{
int count = Count;
if (count < 2) { return 0.0; }
int s_min = 0;
double t_min = 0.0;
double d_min = double.MaxValue;
for (int i = 0; i < count - 1; i++)
{
Line seg = new Line(this[i], this[i + 1]);
double d;
double t;
if (seg.Direction.IsTiny(1e-32))
{
t = 0.0;
d = this[i].DistanceTo(testPoint);
}
else
{
t = seg.ClosestParameter(testPoint);
if (t <= 0.0) { t = 0.0; }
else if (t > 1.0) { t = 1.0; }
d = seg.PointAt(t).DistanceTo(testPoint);
}
if (d < d_min)
{
d_min = d;
t_min = t;
s_min = i;
}
}
return s_min + t_min;
}