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refactor: extract PolygonHelper from AutoNester for shared polygon operations

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Creates PolygonHelper.cs in OpenNest.Engine.BestFit with ExtractPerimeterPolygon
(returning PolygonExtractionResult with polygon + correction vector) and RotatePolygon.
AutoNester.ExtractPerimeterPolygon and RotatePolygon become thin delegates.
Adds MakeSquareDrawing/MakeLShapeDrawing to TestHelpers and 6 PolygonHelperTests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
AJ Isaacs
2026-03-20 19:56:20 -04:00
parent d39b0ae540
commit 71f28600d1
4 changed files with 203 additions and 59 deletions
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89
OpenNest.Engine/BestFit/PolygonHelper.cs Normal file
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@@ -0,0 +1,89 @@
using OpenNest.Converters;
using OpenNest.Geometry;
using OpenNest.Math;
using System.Linq;
namespace OpenNest.Engine.BestFit
{
public static class PolygonHelper
{
public static PolygonExtractionResult ExtractPerimeterPolygon(Drawing drawing, double halfSpacing)
{
var entities = ConvertProgram.ToGeometry(drawing.Program)
.Where(e => e.Layer != SpecialLayers.Rapid)
.ToList();
if (entities.Count == 0)
return new PolygonExtractionResult(null, Vector.Zero);
var definedShape = new ShapeProfile(entities);
var perimeter = definedShape.Perimeter;
if (perimeter == null)
return new PolygonExtractionResult(null, Vector.Zero);
// Compute the perimeter bounding box before inflation for coordinate correction.
perimeter.UpdateBounds();
var perimeterBb = perimeter.BoundingBox;
// Inflate by half-spacing if spacing is non-zero.
Shape inflated;
if (halfSpacing > 0)
{
var offsetEntity = perimeter.OffsetEntity(halfSpacing, OffsetSide.Left);
inflated = offsetEntity as Shape ?? perimeter;
}
else
{
inflated = perimeter;
}
// Convert to polygon with circumscribed arcs for tight nesting.
var polygon = inflated.ToPolygonWithTolerance(0.01, circumscribe: true);
if (polygon.Vertices.Count < 3)
return new PolygonExtractionResult(null, Vector.Zero);
// Compute correction: difference between program origin and perimeter origin.
// Part.CreateAtOrigin normalizes to program bbox; polygon normalizes to perimeter bbox.
var programBb = drawing.Program.BoundingBox();
var correction = new Vector(
perimeterBb.Left - programBb.Location.X,
perimeterBb.Bottom - programBb.Location.Y);
// Normalize: move reference point to origin.
polygon.UpdateBounds();
var bb = polygon.BoundingBox;
polygon.Offset(-bb.Left, -bb.Bottom);
return new PolygonExtractionResult(polygon, correction);
}
public static Polygon RotatePolygon(Polygon polygon, double angle)
{
if (angle.IsEqualTo(0))
return polygon;
var result = new Polygon();
var cos = System.Math.Cos(angle);
var sin = System.Math.Sin(angle);
foreach (var v in polygon.Vertices)
{
result.Vertices.Add(new Vector(
v.X * cos - v.Y * sin,
v.X * sin + v.Y * cos));
}
// Re-normalize to origin.
result.UpdateBounds();
var bb = result.BoundingBox;
result.Offset(-bb.Left, -bb.Bottom);
return result;
}
}
public record PolygonExtractionResult(Polygon Polygon, Vector Correction);
}

61
OpenNest.Engine/Nfp/AutoNester.cs
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@@ -1,4 +1,3 @@
using OpenNest.Converters;
using OpenNest.Geometry;
using OpenNest.Math;
using System;
@@ -203,44 +202,7 @@ namespace OpenNest.Engine.Nfp
/// </summary>
private static Polygon ExtractPerimeterPolygon(Drawing drawing, double halfSpacing)
{
var entities = ConvertProgram.ToGeometry(drawing.Program)
.Where(e => e.Layer != SpecialLayers.Rapid)
.ToList();
if (entities.Count == 0)
return null;
var definedShape = new ShapeProfile(entities);
var perimeter = definedShape.Perimeter;
if (perimeter == null)
return null;
// Inflate by half-spacing if spacing is non-zero.
Shape inflated;
if (halfSpacing > 0)
{
var offsetEntity = perimeter.OffsetEntity(halfSpacing, OffsetSide.Left);
inflated = offsetEntity as Shape ?? perimeter;
}
else
{
inflated = perimeter;
}
// Convert to polygon with circumscribed arcs for tight nesting.
var polygon = inflated.ToPolygonWithTolerance(0.01, circumscribe: true);
if (polygon.Vertices.Count < 3)
return null;
// Normalize: move reference point to origin.
polygon.UpdateBounds();
var bb = polygon.BoundingBox;
polygon.Offset(-bb.Left, -bb.Bottom);
return polygon;
return BestFit.PolygonHelper.ExtractPerimeterPolygon(drawing, halfSpacing).Polygon;
}
/// <summary>
@@ -320,26 +282,7 @@ namespace OpenNest.Engine.Nfp
/// </summary>
private static Polygon RotatePolygon(Polygon polygon, double angle)
{
if (angle.IsEqualTo(0))
return polygon;
var result = new Polygon();
var cos = System.Math.Cos(angle);
var sin = System.Math.Sin(angle);
foreach (var v in polygon.Vertices)
{
result.Vertices.Add(new Vector(
v.X * cos - v.Y * sin,
v.X * sin + v.Y * cos));
}
// Re-normalize to origin.
result.UpdateBounds();
var bb = result.BoundingBox;
result.Offset(-bb.Left, -bb.Bottom);
return result;
return BestFit.PolygonHelper.RotatePolygon(polygon, angle);
}
}
}

88
OpenNest.Tests/PolygonHelperTests.cs Normal file
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@@ -0,0 +1,88 @@
using OpenNest.CNC;
using OpenNest.Engine.BestFit;
using OpenNest.Geometry;
using OpenNest.Math;
namespace OpenNest.Tests;
public class PolygonHelperTests
{
[Fact]
public void ExtractPerimeterPolygon_ReturnsPolygon_ForValidDrawing()
{
var drawing = TestHelpers.MakeSquareDrawing();
var result = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
Assert.NotNull(result.Polygon);
Assert.True(result.Polygon.Vertices.Count >= 4);
}
[Fact]
public void ExtractPerimeterPolygon_InflatesPolygon_WhenSpacingNonZero()
{
var drawing = TestHelpers.MakeSquareDrawing(10);
var noSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
var withSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 1);
noSpacing.Polygon.UpdateBounds();
withSpacing.Polygon.UpdateBounds();
// The offset polygon should differ in size from the non-offset polygon.
// OffsetSide.Left offsets outward or inward depending on winding,
// but either way the result must be a different size.
Assert.True(
System.Math.Abs(withSpacing.Polygon.BoundingBox.Width - noSpacing.Polygon.BoundingBox.Width) > 0.5,
$"Expected polygon width to differ by >0.5 with 1mm spacing. " +
$"No-spacing width: {noSpacing.Polygon.BoundingBox.Width:F3}, " +
$"With-spacing width: {withSpacing.Polygon.BoundingBox.Width:F3}");
}
[Fact]
public void ExtractPerimeterPolygon_ReturnsNull_ForEmptyDrawing()
{
var pgm = new Program();
var drawing = new Drawing("empty", pgm);
var result = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
Assert.Null(result.Polygon);
}
[Fact]
public void ExtractPerimeterPolygon_CorrectionVector_ReflectsOriginDifference()
{
var drawing = TestHelpers.MakeSquareDrawing();
var result = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
Assert.NotNull(result.Polygon);
Assert.True(System.Math.Abs(result.Correction.X) < 1);
Assert.True(System.Math.Abs(result.Correction.Y) < 1);
}
[Fact]
public void RotatePolygon_AtZero_ReturnsSamePolygon()
{
var polygon = new Polygon();
polygon.Vertices.Add(new Vector(0, 0));
polygon.Vertices.Add(new Vector(10, 0));
polygon.Vertices.Add(new Vector(10, 10));
polygon.Vertices.Add(new Vector(0, 10));
polygon.UpdateBounds();
var rotated = PolygonHelper.RotatePolygon(polygon, 0);
Assert.Same(polygon, rotated);
}
[Fact]
public void RotatePolygon_At90Degrees_SwapsDimensions()
{
var polygon = new Polygon();
polygon.Vertices.Add(new Vector(0, 0));
polygon.Vertices.Add(new Vector(20, 0));
polygon.Vertices.Add(new Vector(20, 10));
polygon.Vertices.Add(new Vector(0, 10));
polygon.UpdateBounds();
var rotated = PolygonHelper.RotatePolygon(polygon, Angle.HalfPI);
rotated.UpdateBounds();
Assert.True(System.Math.Abs(rotated.BoundingBox.Width - 10) < 0.1);
Assert.True(System.Math.Abs(rotated.BoundingBox.Length - 20) < 0.1);
}
}

24
OpenNest.Tests/TestHelpers.cs
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@@ -24,4 +24,28 @@ internal static class TestHelpers
plate.Parts.Add(p);
return plate;
}
public static Drawing MakeSquareDrawing(double size = 10)
{
var pgm = new Program();
pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
pgm.Codes.Add(new LinearMove(new Vector(size, 0)));
pgm.Codes.Add(new LinearMove(new Vector(size, size)));
pgm.Codes.Add(new LinearMove(new Vector(0, size)));
pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
return new Drawing("square", pgm);
}
public static Drawing MakeLShapeDrawing()
{
var pgm = new Program();
pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
pgm.Codes.Add(new LinearMove(new Vector(10, 0)));
pgm.Codes.Add(new LinearMove(new Vector(10, 5)));
pgm.Codes.Add(new LinearMove(new Vector(5, 5)));
pgm.Codes.Add(new LinearMove(new Vector(5, 10)));
pgm.Codes.Add(new LinearMove(new Vector(0, 10)));
pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
return new Drawing("lshape", pgm);
}
}