/// <summary>
/// Constructs a ruled surface between two curves.
/// <em>Follows the algorithm at page 337 of The NURBS Book by Piegl and Tiller.</em>
/// </summary>
/// <param name="curveA">The first curve.</param>
/// <param name="curveB">The second curve.</param>
/// <returns>A ruled surface.</returns>
public static NurbsSurface Ruled(NurbsBase curveA, NurbsBase curveB)
{
IList <NurbsBase> curves = new[] { curveA, curveB };
curves = CurveHelpers.NormalizedDegree(curves);
curves = CurveHelpers.NormalizedKnots(curves);
return(new NurbsSurface(1, curves[0].Degree, new KnotVector(1, 2), curves[0].Knots,
new List <List <Point4> > {
curves[0].ControlPoints, curves[1].ControlPoints
}));
}
/// <summary>
/// Constructs a NURBS surface from a set of NURBS curves.<br/>
/// </summary>
/// <param name="curves">Set of a minimum of two curves to create the surface.</param>
/// <param name="loftType">Enum to choose the type of loft generation.</param>
/// <returns>A NURBS surface.</returns>
public static NurbsSurface FromLoft(IList <NurbsBase> curves, LoftType loftType = LoftType.Normal)
{
if (curves == null)
{
throw new ArgumentException("An invalid number of curves to perform the loft.");
}
if (curves.Count < 2)
{
throw new ArgumentException("An invalid number of curves to perform the loft.");
}
if (curves.Any(x => x == null))
{
throw new ArgumentException("The input set contains null curves.");
}
bool isClosed = curves[0].IsClosed;
foreach (NurbsBase c in curves.Skip(1))
{
if (isClosed != c.IsClosed)
{
throw new ArgumentException("Loft only works if all curves are open, or all curves are closed.");
}
}
// Copy curves for possible operation of homogenization.
IList <NurbsBase> copyCurves = new List <NurbsBase>(curves);
// Clamp curves if periodic.
if (copyCurves[0].IsPeriodic)
{
for (int i = 0; i < copyCurves.Count; i++)
{
copyCurves[i] = copyCurves[i].ClampEnds();
}
}
// If necessary, the curves can be brought to a common degree and knots, as we do for the ruled surface.
// In fact, the ruled surface is a special case of a skinned surface.
if (copyCurves.Any(c => c.Degree != copyCurves[0].Degree))
{
copyCurves = CurveHelpers.NormalizedDegree(copyCurves);
copyCurves = CurveHelpers.NormalizedKnots(copyCurves);
}
int degreeV = copyCurves[0].Degree;
int degreeU = 3;
KnotVector knotVectorU = new KnotVector();
KnotVector knotVectorV = copyCurves[0].Knots;
List <List <Point4> > surfaceControlPoints = new List <List <Point4> >();
switch (loftType)
{
case LoftType.Normal:
List <List <Point4> > tempPts = new List <List <Point4> >();
for (int n = 0; n < copyCurves[0].ControlPointLocations.Count; n++)
{
List <Point3> pts = copyCurves.Select(c => c.ControlPointLocations[n]).ToList();
NurbsBase crv = Fitting.Curve.Interpolated(pts, degreeU);
tempPts.Add(crv.ControlPoints);
knotVectorU = crv.Knots;
}
surfaceControlPoints = CollectionHelpers.Transpose2DArray(tempPts);
break;
case LoftType.Loose:
surfaceControlPoints = copyCurves.Select(c => c.ControlPoints).ToList();
knotVectorU = new KnotVector(degreeU, copyCurves.Count);
break;
}
return(new NurbsSurface(degreeU, degreeV, knotVectorU, knotVectorV, surfaceControlPoints));
}