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fix: eliminate endpoint gaps in EllipseConverter arc output

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EllipseConverter computed arc radius from start point only, causing
~0.0009 unit gaps between consecutive arcs. Use circumcircle of
(start, mid, end) points so both endpoints lie exactly on the arc.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
AJ Isaacs
2026-03-28 16:37:01 -04:00
parent 048b10a1e9
commit 1c2b569ff4
2 changed files with 33 additions and 5 deletions
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30
OpenNest.Core/Geometry/EllipseConverter.cs
View File

@@ -64,6 +64,25 @@ namespace OpenNest.Geometry
return new Vector(p1.X + s * n1.X, p1.Y + s * n1.Y);
}
internal static Vector Circumcenter(Vector a, Vector b, Vector c)
{
var ax = a.X - c.X;
var ay = a.Y - c.Y;
var bx = b.X - c.X;
var by = b.Y - c.Y;
var D = 2.0 * (ax * by - ay * bx);
if (System.Math.Abs(D) < 1e-10)
return Vector.Invalid;
var a2 = ax * ax + ay * ay;
var b2 = bx * bx + by * by;
var ux = (by * a2 - ay * b2) / D;
var uy = (ax * b2 - bx * a2) / D;
return new Vector(ux + c.X, uy + c.Y);
}
public static List<Entity> Convert(Vector center, double semiMajor, double semiMinor,
double rotation, double startParam, double endParam, double tolerance = 0.001)
{
@@ -185,11 +204,20 @@ namespace OpenNest.Geometry
{
var p0 = EvaluatePoint(semiMajor, semiMinor, rotation, ellipseCenter, t0);
var p1 = EvaluatePoint(semiMajor, semiMinor, rotation, ellipseCenter, t1);
var pMid = EvaluatePoint(semiMajor, semiMinor, rotation, ellipseCenter, (t0 + t1) / 2);
// Use circumcircle of (p0, pMid, p1) so the arc passes through both
// endpoints exactly, eliminating gaps between adjacent arcs.
var cc = Circumcenter(p0, pMid, p1);
if (cc.IsValid())
{
arcCenter = cc;
radius = p0.DistanceTo(cc);
}
var startAngle = System.Math.Atan2(p0.Y - arcCenter.Y, p0.X - arcCenter.X);
var endAngle = System.Math.Atan2(p1.Y - arcCenter.Y, p1.X - arcCenter.X);
var pMid = EvaluatePoint(semiMajor, semiMinor, rotation, ellipseCenter, (t0 + t1) / 2);
var points = new List<Vector> { p0, pMid, p1 };
var isReversed = SumSignedAngles(arcCenter, points) < 0;

8
OpenNest.Tests/EllipseConverterTests.cs
View File

@@ -172,15 +172,15 @@ public class EllipseConverterTests
var current = (Arc)result[i];
var next = (Arc)result[i + 1];
var gap = current.EndPoint().DistanceTo(next.StartPoint());
Assert.True(gap < 0.001,
$"Gap of {gap:F6} between arc {i} and arc {i + 1}");
Assert.True(gap < 1e-6,
$"Gap of {gap:E4} between arc {i} and arc {i + 1}");
}
var lastArc = (Arc)result[^1];
var firstArc = (Arc)result[0];
var closingGap = lastArc.EndPoint().DistanceTo(firstArc.StartPoint());
Assert.True(closingGap < 0.001,
$"Closing gap of {closingGap:F6}");
Assert.True(closingGap < 1e-6,
$"Closing gap of {closingGap:E4}");
}
[Fact]