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Sample BSpline2D.AddToGraphicsPath on 0..1 #485

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Merged
dsn27 merged 1 commit into from
Oct 17, 2026
Merged

Sample BSpline2D.AddToGraphicsPath on 0..1 #485

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3 changes: 1 addition & 2 deletions CADability/BSpline2D.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1668,10 +1668,9 @@ public override void AddToGraphicsPath(System.Drawing.Drawing2D.GraphicsPath pat
// Notfalls Darstellung als Polyline
int l = poles.Length * 4 + 2;
PointF[] ppf = new PointF[l];
double du = (endParam - startParam) / (l - 1);
for (int i = 0; i < l; ++i)
{
ppf[i] = PointAt(startParam + i * du).PointF;
ppf[i] = PointAt((double)i / (l - 1)).PointF; // PointAt expects 0..1, not the knot parameter
}
if (!forward) Array.Reverse(ppf);
path.AddLines(ppf);
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31 changes: 31 additions & 0 deletions tests/CADability.Tests/BSpline2DGraphicsPathTests.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
#if WINDOWS
using CADability.Curve2D;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Drawing;
using System.Drawing.Drawing2D;

namespace CADability.Tests
{
/// <summary>
/// <see cref="BSpline2D.AddToGraphicsPath"/> passed knot parameters to <see cref="BSpline2D.PointAt"/>, which expects
/// 0..1, so a spline whose knots do not run from 0 to 1 was drawn through wrong points. GDI+ only works on Windows, so
/// this test only runs there.
/// </summary>
[TestClass]
public class BSpline2DGraphicsPathTests
{
[TestMethod]
public void ASplineWithKnotsBeyondOneIsSampledOnTheCurve()
{
BSpline2D bsp = new BSpline2D(new[] { new GeoPoint2D(0, 0), new GeoPoint2D(1, 3), new GeoPoint2D(4, 3), new GeoPoint2D(5, 0) }, null, new double[] { 0, 5 }, new[] { 4, 4 }, 3, false, 0, 5);
GraphicsPath path = new GraphicsPath();
bsp.AddToGraphicsPath(path, true);
PointF[] points = path.PathPoints;
Assert.AreEqual(bsp.StartPoint.PointF, points[0]);
Assert.AreEqual(bsp.EndPoint.PointF, points[points.Length - 1]);
// MinDistance and not Distance: BSpline2D.Distance returns double.MaxValue for these points
foreach (PointF p in points) Assert.AreEqual(0.0, bsp.MinDistance(new GeoPoint2D(p.X, p.Y)), 1e-4);
}
}
}
#endif
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