fix: refinement with constraints without holes

Previously, refinement was not working correctly with constraints without restoring the boundaries. The constraints were ignored when these options were selected.
andywiecko · Oct 9, 2024 · f4ac16a · f4ac16a
1 parent 4b8a014
commit f4ac16a
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Showing 3 changed files with 63 additions and 5 deletions.
diff --git a/Runtime/Triangulator.cs b/Runtime/Triangulator.cs
@@ -1,4 +1,4 @@
-/*
+/*
 MIT License
 
 Copyright (c) 2021 Andrzej Więckowski, Ph.D., https://github.com/andywiecko/BurstTriangulator
@@ -2592,7 +2592,7 @@ public void Execute(Allocator allocator, bool refineMesh, bool constrainBoundary
                 {
                     for (int he = 0; he < constrainedHalfedges.Length; he++)
                     {
-                        constrainedHalfedges[he] = halfedges[he] == -1;
+                        constrainedHalfedges[he] |= halfedges[he] == -1;
                     }
                 }
 

diff --git a/Tests/TriangulatorGenericsEditorTests.cs b/Tests/TriangulatorGenericsEditorTests.cs
@@ -2301,5 +2301,49 @@ public void HalfedgesForTriangulationWithRefinementTest()
                 false, false, false, false, true, true,
             }));
         }
+
+        [Test]
+        public void ConstraintsArePresentWithRefinementButWithoutHolesTest()
+        {
+#if UNITY_MATHEMATICS_FIXEDPOINT
+            if (typeof(T) == typeof(fp2))
+            {
+                Assert.Ignore(
+                    "This input gets stuck with this configuration.\n" +
+                    "\n" +
+                    "Explanation: When constraints and refinement are enabled, but restore boundary is not, \n" +
+                    "the refinement procedure can quickly get stuck and produce an excessive number of triangles. \n" +
+                    "According to the literature, there are many examples suggesting that one should plant holes first, \n" +
+                    "then refine the mesh. These small triangles fall outside of `fp2` precision."
+                );
+            }
+#endif
+
+            using var positions = new NativeArray<T>(LakeSuperior.Points.DynamicCast<T>(), Allocator.Persistent);
+            using var holes = new NativeArray<T>(LakeSuperior.Holes.DynamicCast<T>(), Allocator.Persistent);
+            using var constraints = new NativeArray<int>(LakeSuperior.Constraints, 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 }
+            };
+
+            triangulator.Run();
+
+            static int NextHalfedge(int he) => he % 3 == 2 ? he - 2 : he + 1;
+            var triangles = triangulator.Output.Triangles;
+            var constrainedHalfedges = triangulator.Output.ConstrainedHalfedges;
+            var visited = new bool[triangulator.Output.Positions.Length];
+            for (int he = 0; he < constrainedHalfedges.Length; he++)
+            {
+                if (constrainedHalfedges[he])
+                {
+                    visited[triangles[he]] = visited[triangles[NextHalfedge(he)]] = true;
+                }
+            }
+            // Naive check if all points are "visited".
+            Assert.That(visited[..LakeSuperior.Points.Length], Has.All.True);
+        }
     }
-}
+}
diff --git a/Tests/UnsafeTriangulatorEditorTests.cs b/Tests/UnsafeTriangulatorEditorTests.cs
@@ -386,9 +386,23 @@ public class UnsafeTriangulatorEditorTestsWithRefinement<T> where T : unmanaged
         [Test]
         public void UnsafeTriangulatorOutputTrianglesTest([Values] bool constrain, [Values] bool refine, [Values] bool holes)
         {
-            using var positions = new NativeArray<T>(LakeSuperior.Points.Scale(1000, typeof(T) == typeof(int2)).DynamicCast<T>(), Allocator.Persistent);
+#if UNITY_MATHEMATICS_FIXEDPOINT
+            if (typeof(T) == typeof(fp2) && constrain && refine && !holes)
+            {
+                Assert.Ignore(
+                    "This input gets stuck with this configuration.\n" +
+                    "\n" +
+                    "Explanation: When constraints and refinement are enabled, but restore boundary is not, \n" +
+                    "the refinement procedure can quickly get stuck and produce an excessive number of triangles. \n" +
+                    "According to the literature, there are many examples suggesting that one should plant holes first, \n" +
+                    "then refine the mesh. These small triangles fall outside of `fp2` precision."
+                );
+            }
+#endif
+
+            using var positions = new NativeArray<T>(LakeSuperior.Points.DynamicCast<T>(), Allocator.Persistent);
             using var constraints = new NativeArray<int>(LakeSuperior.Constraints, Allocator.Persistent);
-            using var holesSeeds = new NativeArray<T>(LakeSuperior.Holes.Scale(1000, typeof(T) == typeof(int2)).DynamicCast<T>(), Allocator.Persistent);
+            using var holesSeeds = new NativeArray<T>(LakeSuperior.Holes.DynamicCast<T>(), Allocator.Persistent);
             using var triangles = new NativeList<int>(64, Allocator.Persistent);
             using var triangulator = new Triangulator<T>(Allocator.Persistent)
             {