public static NurbsPoint DeBoor(int p, List <NurbsPoint> controlPoints, decimal u, decimal[] knotVector)
{
if (u.AlmostEquals(0M))
{
return(controlPoints.First());
}
if (u.AlmostEquals(1M))
{
return(controlPoints.Last());
}
var k = FindSpan(u, knotVector);
var s = NurbsLogic.CheckMultiplicity(knotVector, u);
NurbsPoint point;
if (u.GreaterThanOrEqualTo(knotVector[k]) && u.LessThan(knotVector[k + 1]))
{
var h = p - s;
if (h == 0)
{
return(controlPoints[k - s]);
}
var points = new List <Point4D> [h + 1];
points[0] = controlPoints.ToPoint4DList();
for (var r = 1; r <= h; r++)
{
/*points[r] = new List<Point4D>(k - s + 1);
* for (var i = 0; i <= k - s + 1; i++)
* {
* points[r].Add(new Point4D(-1, -1, -1, -1));
* }*/
points[r] = controlPoints.ToPoint4DList();
for (var i = k - p + r; i <= k - s; i++)
{
if (points[r - 1][i - 1] == null || points[r - 1][i] == null)
{
continue;
}
// ReSharper disable once InconsistentNaming
var a_ir = (double)((u - knotVector[i]) / (knotVector[i + p - r + 1] - knotVector[i]));
var x = ((1 - a_ir) * points[r - 1][i - 1].X) + (a_ir * points[r - 1][i].X);
var y = ((1 - a_ir) * points[r - 1][i - 1].Y) + (a_ir * points[r - 1][i].Y);
var z = ((1 - a_ir) * points[r - 1][i - 1].Z) + (a_ir * points[r - 1][i].Z);
var weight = ((1 - a_ir) * points[r - 1][i - 1].Weight) + (a_ir * points[r - 1][i].Weight);
points[r][i] = new Point4D(x, y, z, weight);
}
}
point = points[h][k - s].ToNurbsPoint();
}
else
{
// ReSharper disable once UnthrowableException
throw new IndexOutOfRangeException("u not in [u_k, u_k+1)");
}
return(point);
}
public static int CheckMultiplicity(decimal[] knotVector, decimal knot) => knotVector.Count(u => knot.AlmostEquals(u));
