public static NurbsPoint DeBoorSurface(
List <List <NurbsPoint> > controlNet,
decimal u,
decimal[] knotU,
decimal v,
decimal[] knotV)
{
var cPointsU = controlNet.First();
var cPointsV = controlNet.Transpose().First();
var p = knotU.Length - cPointsU.Count - 1;
var q = knotV.Length - cPointsV.Count - 1;
u = Math.Round(u, 21);
v = Math.Round(v, 21);
var magic = 0;
switch (u)
{
case 0:
magic += 1;
break;
case 1:
magic += 3;
break;
default:
magic += 2;
break;
}
switch (v)
{
case 0:
magic += 0;
break;
case 1:
magic += 6;
break;
default:
magic += 3;
break;
}
switch (magic)
{
case 1:
return(controlNet.First().First());
case 2:
return(NurbsLogic.DeBoor(p, controlNet.First(), u, knotU));
case 3:
return(controlNet.First().Last());
case 4:
return(NurbsLogic.DeBoor(q, controlNet.Transpose().First(), v, knotV));
case 5:
break;
case 6:
return(NurbsLogic.DeBoor(q, controlNet.Transpose().Last(), v, knotV));
case 7:
return(controlNet.Last().First());
case 8:
return(NurbsLogic.DeBoor(p, controlNet.Last(), u, knotU));
case 9:
return(controlNet.Last().Last());
default:
break;
}
var c = NurbsLogic.FindSpan(u, knotU);
var d = NurbsLogic.FindSpan(v, knotV);
var s = NurbsLogic.CheckMultiplicity(knotU, u);
var t = NurbsLogic.CheckMultiplicity(knotV, v);
NurbsPoint point;
if (u.GreaterThanOrEqualTo(knotU[c]) && u.LessThan(knotU[c + 1]) && v.GreaterThanOrEqualTo(knotV[d]) && v.LessThan(knotV[d + 1]))
{
var P = new NurbsPoint[c - s + 1, d - t + 1];
var Q = new NurbsPoint[c - s + 1];
for (var i = 0; i < P.GetLength(0); i++)
{
for (var j = 0; j < P.GetLength(1); j++)
{
P[i, j] = controlNet[j][i];
}
}
for (var i = 0; i < P.GetLength(0); i++)
{
var Pi = new List <NurbsPoint>();
for (var j = 0; j < P.GetLength(1); j++)
{
Pi.Add(P[i, j]);
}
Q[i] = NurbsLogic.DeBoor(q, Pi, v, knotV);
}
point = NurbsLogic.DeBoor(p, Q.ToList(), u, knotU);
}
else
{
// ReSharper disable once UnthrowableException
throw new IndexOutOfRangeException("u not in [u_c, u_c+1) or v not in [u_d, u_d+1)");
}
return(point);
}
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);
}
