feat: add NfpSlideStrategy for NFP-based best-fit candidate generation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-03-20 20:03:52 -04:00
parent 707ddb80d9
commit 5f4288a786
2 changed files with 203 additions and 0 deletions
--- a/OpenNest.Engine/BestFit/NfpSlideStrategy.cs
+++ b/OpenNest.Engine/BestFit/NfpSlideStrategy.cs
@@ -0,0 +1,100 @@
+using OpenNest.Geometry;
+using System.Collections.Generic;
+
+namespace OpenNest.Engine.BestFit
+{
+    public class NfpSlideStrategy : IBestFitStrategy
+    {
+        private readonly double _part2Rotation;
+
+        public NfpSlideStrategy(double part2Rotation, int type, string description)
+        {
+            _part2Rotation = part2Rotation;
+            Type = type;
+            Description = description;
+        }
+
+        public int Type { get; }
+        public string Description { get; }
+
+        public List<PairCandidate> GenerateCandidates(Drawing drawing, double spacing, double stepSize)
+        {
+            var candidates = new List<PairCandidate>();
+            var halfSpacing = spacing / 2;
+
+            // Extract stationary polygon (Part1 at rotation 0), with spacing applied.
+            var stationaryResult = PolygonHelper.ExtractPerimeterPolygon(drawing, halfSpacing);
+
+            if (stationaryResult.Polygon == null)
+                return candidates;
+
+            var stationaryPoly = stationaryResult.Polygon;
+
+            // Orbiting polygon: same shape rotated to Part2's angle.
+            var orbitingPoly = PolygonHelper.RotatePolygon(stationaryResult.Polygon, _part2Rotation);
+
+            // Compute NFP.
+            var nfp = NoFitPolygon.Compute(stationaryPoly, orbitingPoly);
+
+            if (nfp == null || nfp.Vertices.Count < 3)
+                return candidates;
+
+            // Coordinate correction: NFP offsets are in polygon-space.
+            // Part.CreateAtOrigin uses program bbox origin.
+            var correction = stationaryResult.Correction;
+
+            // Walk NFP boundary — vertices + edge samples.
+            var verts = nfp.Vertices;
+            var vertCount = nfp.IsClosed() ? verts.Count - 1 : verts.Count;
+            var testNumber = 0;
+
+            for (var i = 0; i < vertCount; i++)
+            {
+                // Add vertex candidate.
+                var offset = ApplyCorrection(verts[i], correction);
+                candidates.Add(MakeCandidate(drawing, offset, spacing, testNumber++));
+
+                // Add edge samples for long edges.
+                var next = (i + 1) % vertCount;
+                var dx = verts[next].X - verts[i].X;
+                var dy = verts[next].Y - verts[i].Y;
+                var edgeLength = System.Math.Sqrt(dx * dx + dy * dy);
+
+                if (edgeLength > stepSize)
+                {
+                    var steps = (int)(edgeLength / stepSize);
+                    for (var s = 1; s < steps; s++)
+                    {
+                        var t = (double)s / steps;
+                        var sample = new Vector(
+                            verts[i].X + dx * t,
+                            verts[i].Y + dy * t);
+                        var sampleOffset = ApplyCorrection(sample, correction);
+                        candidates.Add(MakeCandidate(drawing, sampleOffset, spacing, testNumber++));
+                    }
+                }
+            }
+
+            return candidates;
+        }
+
+        private static Vector ApplyCorrection(Vector nfpVertex, Vector correction)
+        {
+            return new Vector(nfpVertex.X + correction.X, nfpVertex.Y + correction.Y);
+        }
+
+        private PairCandidate MakeCandidate(Drawing drawing, Vector offset, double spacing, int testNumber)
+        {
+            return new PairCandidate
+            {
+                Drawing = drawing,
+                Part1Rotation = 0,
+                Part2Rotation = _part2Rotation,
+                Part2Offset = offset,
+                StrategyType = Type,
+                TestNumber = testNumber,
+                Spacing = spacing
+            };
+        }
+    }
+}