fix: refinement produces invalid result

Fixed an issue where refinement could produce invalid results in rare cases, particularly when the input contains subsegment clusters. These invalid cases manifested with addition of points outside the triangulation domain.

Runtime/Triangulator.cs

@@ -3118,7 +3118,7 @@ private void BuildNewTrianglesForStar(int pId, NativeList<int> heQueue, NativeLi
 
                 if (heQueue.IsCreated)
                 {
-                    for (int i = 0; i < pathPoints.Length - 1; i++)
+                    for (int i = 0; i < pathPoints.Length; i++)
                     {
                         var he = heOffset + 3 * i + 1;
                         if (constrainedHalfedges[he] && IsEncroached(he))

Tests/TriangulatorGenericsEditorTests.cs

@@ -1824,30 +1824,32 @@ public void DelaunayTriangulationWithRefinementTest()
                     math.float2(1f, 0.5f),
                     math.float2(0.5f, 0f),
                     math.float2(0f, 0.5f),
+                    math.float2(0.5f, 1f),
                     math.float2(0.8189806f, 0.8189806f),
                     math.float2(0.1810194f, 0.1810194f),
-                    math.float2(0.5f, 1f),
+                    math.float2(0.744f, 1f),
+                    math.float2(1f, 0.744f),
                     math.float2(0.256f, 0f),
                     math.float2(0f, 0.256f),
-                    math.float2(0.744f, 1f),
                 },
                 new []
                 {
                     6, 4, 5,
                     6, 5, 1,
-                    8, 2, 5,
-                    8, 5, 4,
-                    9, 4, 6,
-                    9, 7, 4,
-                    10, 4, 7,
-                    10, 7, 3,
-                    10, 8, 4,
-                    11, 0, 9,
-                    11, 9, 6,
-                    12, 7, 9,
-                    12, 9, 0,
-                    13, 2, 8,
-                    13, 8, 10,
+                    8, 4, 7,
+                    8, 7, 3,
+                    9, 5, 4,
+                    9, 4, 8,
+                    10, 7, 4,
+                    10, 4, 6,
+                    11, 2, 9,
+                    11, 9, 8,
+                    12, 5, 9,
+                    12, 9, 2,
+                    13, 0, 10,
+                    13, 10, 6,
+                    14, 7, 10,
+                    14, 10, 0,
                 }
             )){ TestName = "Test case 1 (square)" },
 
@@ -2345,5 +2347,39 @@ public void ConstraintsArePresentWithRefinementButWithoutHolesTest()
             // Naive check if all points are "visited".
             Assert.That(visited[..LakeSuperior.Points.Length], Has.All.True);
         }
+
+        [Test]
+        public void RefinementWithNeedleConstraintClusterTest()
+        {
+            using var positions = new NativeArray<T>(new[] {
+                math.float2(0, 0),
+                math.float2(9, 0),
+                math.float2(9, 7),
+                math.float2(-1, 7),
+                math.float2(-1, .2f),
+            }.DynamicCast<T>(), Allocator.Persistent);
+            using var constraints = new NativeArray<int>(new[] { 0, 1, 1, 4, }, Allocator.Persistent);
+
+            using var triangulator = new Triangulator<T>(Allocator.Persistent)
+            {
+                Input = { Positions = positions, ConstraintEdges = constraints, HoleSeeds = default },
+                Settings = { RefineMesh = true, Preprocessor = Preprocessor.None, ValidateInput = true, RefinementThresholds = { Area = 10, Angle = math.radians(25) } }
+            };
+
+            triangulator.Run();
+            triangulator.Draw(color: Color.blue);
+
+            var result = triangulator.Output.Positions.AsReadOnly()
+                .Select(i => default(T) switch
+                {
+#if UNITY_MATHEMATICS_FIXEDPOINT
+                    fp2 => math.float2((float)((dynamic)i).x, (float)((dynamic)i).y),
+#endif
+                    _ => (float2)(dynamic)i,
+                })
+                .Select(i => math.all(i >= math.float2(-1, 0) & i <= math.float2(9, 7))).ToArray();
+
+            Assert.That(result, Has.All.True);
+        }
     }
 }