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feat: dual-tangent arc fitting and DXF version export

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Add ArcFit.FitWithDualTangent to constrain replacement arcs to match
tangent directions at both endpoints, preventing kinks without
introducing gaps. Add DXF year selection to CAD converter export.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
AJ Isaacs
2026-03-30 09:16:09 -04:00
parent 9b2322abe9
commit 722f758e94
3 changed files with 124 additions and 2 deletions
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54
OpenNest.Core/Geometry/ArcFit.cs
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@@ -56,6 +56,60 @@ namespace OpenNest.Geometry
return (new Vector(cx, cy), radius, MaxRadialDeviation(points, cx, cy, radius));
}
/// <summary>
/// Fits a circular arc constrained to be tangent to the given directions at both
/// the first and last points. The center lies at the intersection of the normals
/// at P1 and Pn, guaranteeing the arc departs P1 in the start direction and arrives
/// at Pn in the end direction. Uses the radius from P1 (exact start tangent);
/// deviation includes any endpoint gap at Pn.
/// </summary>
internal static (Vector center, double radius, double deviation) FitWithDualTangent(
List<Vector> points, Vector startTangent, Vector endTangent)
{
if (points.Count < 3)
return (Vector.Invalid, 0, double.MaxValue);
var p1 = points[0];
var pn = points[^1];
var stLen = System.Math.Sqrt(startTangent.X * startTangent.X + startTangent.Y * startTangent.Y);
var etLen = System.Math.Sqrt(endTangent.X * endTangent.X + endTangent.Y * endTangent.Y);
if (stLen < 1e-10 || etLen < 1e-10)
return (Vector.Invalid, 0, double.MaxValue);
// Normal to start tangent at P1 (perpendicular)
var n1x = -startTangent.Y / stLen;
var n1y = startTangent.X / stLen;
// Normal to end tangent at Pn
var n2x = -endTangent.Y / etLen;
var n2y = endTangent.X / etLen;
// Solve: P1 + t1*N1 = Pn + t2*N2
var det = n1x * (-n2y) - (-n2x) * n1y;
if (System.Math.Abs(det) < 1e-10)
return (Vector.Invalid, 0, double.MaxValue);
var dx = pn.X - p1.X;
var dy = pn.Y - p1.Y;
var t1 = (dx * (-n2y) - (-n2x) * dy) / det;
var cx = p1.X + t1 * n1x;
var cy = p1.Y + t1 * n1y;
// Use radius from P1 (guarantees exact start tangent and passes through P1)
var r1 = System.Math.Sqrt((cx - p1.X) * (cx - p1.X) + (cy - p1.Y) * (cy - p1.Y));
if (r1 < 1e-10)
return (Vector.Invalid, 0, double.MaxValue);
// Measure endpoint gap at Pn
var r2 = System.Math.Sqrt((cx - pn.X) * (cx - pn.X) + (cy - pn.Y) * (cy - pn.Y));
var endpointDev = System.Math.Abs(r2 - r1);
var interiorDev = MaxRadialDeviation(points, cx, cy, r1);
return (new Vector(cx, cy), r1, System.Math.Max(endpointDev, interiorDev));
}
/// <summary>
/// Computes the maximum radial deviation of interior points from a circle.
/// </summary>