fix(engine): skip intersecting parts as obstacles during compactor push

Parts that already overlap the moving group are now excluded from the
obstacle list so they don't block the push direction.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Engine/Fill/Compactor.cs

@@ -1,6 +1,7 @@
 using OpenNest.Geometry;
 using System.Collections.Generic;
 using System.Linq;
+using OpenNest.Math;
 
 namespace OpenNest.Engine.Fill
 {
@@ -14,7 +15,7 @@ namespace OpenNest.Engine.Fill
         public static double Push(List<Part> movingParts, Plate plate, PushDirection direction)
         {
             var obstacleParts = plate.Parts
-                .Where(p => !movingParts.Contains(p))
+                .Where(p => !movingParts.Contains(p) && !IntersectsAny(p, movingParts))
                 .ToList();
 
             return Push(movingParts, obstacleParts, plate.WorkArea(), plate.PartSpacing, direction);
@@ -26,7 +27,7 @@ namespace OpenNest.Engine.Fill
         public static double Push(List<Part> movingParts, Plate plate, double angle)
         {
             var obstacleParts = plate.Parts
-                .Where(p => !movingParts.Contains(p))
+                .Where(p => !movingParts.Contains(p) && !IntersectsAny(p, movingParts))
                 .ToList();
 
             var direction = new Vector(System.Math.Cos(angle), System.Math.Sin(angle));
@@ -99,6 +100,13 @@ namespace OpenNest.Engine.Fill
                         : PartGeometry.GetPerimeterEntities(obstacleParts[i]);
 
                     var d = SpatialQuery.DirectionalDistance(movingEntities, obstacleEntities[i], direction);
+                    if (d <= Tolerance.Epsilon
+                        && partSpacing <= Tolerance.Epsilon
+                        && CanNudgeWithoutOverlap(moving, obstacleParts[i], direction))
+                    {
+                        continue;
+                    }
+
                     if (d < distance)
                         distance = d;
                 }
@@ -115,6 +123,31 @@ namespace OpenNest.Engine.Fill
             return 0;
         }
 
+        private static bool IntersectsAny(Part candidate, List<Part> parts)
+        {
+            for (var i = 0; i < parts.Count; i++)
+            {
+                if (candidate.Intersects(parts[i], out _))
+                    return true;
+            }
+            return false;
+        }
+
+        private static bool CanNudgeWithoutOverlap(Part moving, Part obstacle, Vector direction)
+        {
+            var nudge = direction * (Tolerance.Epsilon * 10);
+
+            moving.Offset(nudge);
+            try
+            {
+                return !moving.Intersects(obstacle, out _);
+            }
+            finally
+            {
+                moving.Offset(-nudge);
+            }
+        }
+
         public static double Push(List<Part> movingParts, List<Part> obstacleParts,
             Box workArea, double partSpacing, PushDirection direction)
         {
@@ -130,7 +163,7 @@ namespace OpenNest.Engine.Fill
         public static double PushBoundingBox(List<Part> movingParts, Plate plate, PushDirection direction)
         {
             var obstacleParts = plate.Parts
-                .Where(p => !movingParts.Contains(p))
+                .Where(p => !movingParts.Contains(p) && !IntersectsAny(p, movingParts))
                 .ToList();
 
             return PushBoundingBox(movingParts, obstacleParts, plate.WorkArea(), plate.PartSpacing, direction);

OpenNest.Tests/Fill/CompactorTests.cs

@@ -97,6 +97,33 @@ namespace OpenNest.Tests.Fill
             return part;
         }
 
+        private static Drawing MakeTriangleDrawing(params Vector[] points)
+        {
+            var pgm = new OpenNest.CNC.Program();
+            pgm.Codes.Add(new OpenNest.CNC.RapidMove(points[0]));
+
+            for (var i = 1; i < points.Length; i++)
+                pgm.Codes.Add(new OpenNest.CNC.LinearMove(points[i]));
+
+            pgm.Codes.Add(new OpenNest.CNC.LinearMove(points[0]));
+            return new Drawing("triangle", pgm);
+        }
+
+        private static Part MakeTrianglePart(params Vector[] points)
+        {
+            var part = new Part(MakeTriangleDrawing(points));
+            part.UpdateBounds();
+            return part;
+        }
+
+        private static Part MakeTrianglePart(double x, double y, params Vector[] points)
+        {
+            var part = MakeTrianglePart(points);
+            part.Location = new Vector(x, y);
+            part.UpdateBounds();
+            return part;
+        }
+
         [Fact]
         public void Push_Left_MovesPartTowardEdge()
         {
@@ -171,6 +198,86 @@ namespace OpenNest.Tests.Fill
             Assert.NotEqual(distNoSpacing, distWithSpacing);
         }
 
+        [Fact]
+        public void Push_Up_AllowsSharedDiagonalEdgeToSeparate()
+        {
+            var workArea = new Box(0, 0, 20, 20);
+            var obstacle = MakeTrianglePart(
+                new Vector(0, 0),
+                new Vector(10, 0),
+                new Vector(0, 10));
+            var movingPart = MakeTrianglePart(
+                new Vector(0, 10),
+                new Vector(10, 0),
+                new Vector(10, 10));
+
+            var distance = Compactor.Push(
+                new List<Part> { movingPart },
+                new List<Part> { obstacle },
+                workArea,
+                0,
+                PushDirection.Up);
+
+            Assert.True(distance > 0);
+            Assert.True(movingPart.BoundingBox.Top > 19.9);
+            Assert.False(movingPart.Intersects(obstacle, out _));
+        }
+
+        [Fact]
+        public void Push_Up_MovesAfterRightTriangleIsPushedLeftIntoSharedEdge()
+        {
+            var workArea = new Box(0, 0, 24, 24);
+            var leftTriangle = MakeTrianglePart(
+                2, 2,
+                new Vector(0, 0),
+                new Vector(8, 0),
+                new Vector(4, 10));
+            var rightTriangle = MakeTrianglePart(
+                14, 4,
+                new Vector(0, 10),
+                new Vector(8, 10),
+                new Vector(4, 0));
+
+            var moving = new List<Part> { rightTriangle };
+            var obstacles = new List<Part> { leftTriangle };
+
+            var leftDistance = Compactor.Push(moving, obstacles, workArea, 0, PushDirection.Left);
+            var yBeforePushUp = rightTriangle.Location.Y;
+            var bottomBeforePushUp = rightTriangle.BoundingBox.Bottom;
+
+            var upDistance = Compactor.Push(moving, obstacles, workArea, 0, PushDirection.Up);
+
+            Assert.True(leftDistance > 0);
+            Assert.True(upDistance > 0);
+            Assert.True(rightTriangle.Location.Y > yBeforePushUp);
+            Assert.True(rightTriangle.BoundingBox.Bottom > bottomBeforePushUp);
+            Assert.False(rightTriangle.Intersects(leftTriangle, out _));
+        }
+
+        [Fact]
+        public void Push_Left_BlocksWhenSharedDiagonalEdgeWouldOverlap()
+        {
+            var workArea = new Box(0, 0, 20, 20);
+            var obstacle = MakeTrianglePart(
+                new Vector(0, 0),
+                new Vector(10, 0),
+                new Vector(0, 10));
+            var movingPart = MakeTrianglePart(
+                new Vector(0, 10),
+                new Vector(10, 0),
+                new Vector(10, 10));
+
+            var distance = Compactor.Push(
+                new List<Part> { movingPart },
+                new List<Part> { obstacle },
+                workArea,
+                0,
+                PushDirection.Left);
+
+            Assert.Equal(0, distance);
+            Assert.Equal(0, movingPart.BoundingBox.Left);
+        }
+
         [Fact]
         public void Push_AngleLeft_MovesPartTowardEdge()
         {