private Curve ExtendCurveToEndpoints(Curve curve)
{
Point p = this.EdgePathPoint(0);
if (!ApproximateComparer.Close(p, curve.Start))
{
Curve nc = new Curve();
nc.AddSegs(new LineSegment(p, curve.Start), curve);
curve = nc;
}
p = this.EdgePathPoint(edgePath.Count);
if (!ApproximateComparer.Close(p, curve.End))
{
curve.AddSegment(new LineSegment(curve.End, p));
}
return(curve);
}
private Curve ExtendCurveToEndpoints(Curve curve)
{
Point p = headSite.Point;
if (!ApproximateComparer.Close(p, curve.Start))
{
Curve nc = new Curve();
nc.AddSegs(new LineSegment(p, curve.Start), curve);
curve = nc;
}
p = TailSite.Point;
if (!ApproximateComparer.Close(p, curve.End))
{
curve.AddSegment(new LineSegment(curve.End, p));
}
return(curve);
}
/// <summary>
/// Following "Biarc approximation of NURBS curves", Les A. Piegl, and Wayne Tiller. The paper has a bug in V, where they write that v=p0+p4, it is p0-p4.
/// Also I treat special cases differently.
/// </summary>
/// <param name="p0"></param>
/// <param name="ts"></param>
/// <param name="p4"></param>
/// <param name="te"></param>
/// <returns></returns>
internal static ICurve BiArc(Point p0, Point ts, Point p4, Point te)
{
Debug.Assert(ApproximateComparer.Close(ts.LengthSquared, 1));
Debug.Assert(ApproximateComparer.Close(te.LengthSquared, 1));
var v = p0 - p4;
if (v.Length < ApproximateComparer.DistanceEpsilon)
{
return(null);
}
var vtse = v * (ts - te);
var tste = -ts * te;
//solving a quadratic equation
var a = 2 * (tste - 1);
var b = 2 * vtse;
var c = v * v;
double al;
if (Math.Abs(a) < ApproximateComparer.DistanceEpsilon) //we have b*al+c=0
{
if (Math.Abs(b) > ApproximateComparer.DistanceEpsilon)
{
al = -c / b;
}
else
{
return(null);
}
}
else
{
var d = b * b - 4 * a * c;
Debug.Assert(d >= -ApproximateComparer.Tolerance);
if (d < 0)
{
d = 0;
}
d = Math.Sqrt(d);
al = (-b + d) / (2 * a);
if (al < 0)
{
al = (-b - d) / (2 * a);
}
}
var p1 = p0 + al * ts;
var p3 = p4 + al * te;
var p2 = 0.5 * (p1 + p3);
var curve = new Curve();
curve.AddSegs(ArcOn(p0, p1, p2), ArcOn(p2, p3, p4));
//bad input for BiArc. we shouldn't allow such cases during bundle bases construction
if (ts * (p4 - p0) <= 0 && ts * te <= 0)
{
//switch to Bezier
var curve2 = StandardBezier(p0, ts, p4, te);
#if DEBUG && TEST_MSAGL
/*List<DebugCurve> dc = new List<DebugCurve>();
* dc.Add(new DebugCurve(curve));
* dc.Add(new DebugCurve(0.3, "black", curve2));
* dc.Add(new DebugCurve(0.1, "red", new LineSegment(p0, p0 + 3 * ts)));
* dc.Add(new DebugCurve(0.1, "blue", new LineSegment(p4, p4 + 3 * te)));
* LayoutAlgorithmSettings.ShowDebugCurvesEnumeration(dc);*/
#endif
return(curve2);
}
return(curve);
}
