operator that smooths an embedded edge loop in a mesh, with optional …

…projection

mesh_ops/MeshLoopSmooth.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Collections.Generic;
+
+namespace g3
+{
+    public class MeshLoopSmooth
+    {
+        public DMesh3 Mesh;
+        public EdgeLoop Loop;
+
+        public double Alpha = 0.25f;
+        public int Rounds = 10;
+
+        // reproject smoothed position to new location
+        public Func<Vector3d, Vector3f, int, Vector3d> ProjectF;
+
+
+        Vector3d[] SmoothedPostions;
+
+        public MeshLoopSmooth(DMesh3 mesh, EdgeLoop loop)
+        {
+            Mesh = mesh;
+            Loop = loop;
+
+            SmoothedPostions = new Vector3d[Loop.Vertices.Length];
+
+            ProjectF = null;
+        }
+
+
+        public virtual ValidationStatus Validate()
+        {
+            ValidationStatus loopStatus = MeshValidation.IsEdgeLoop(Mesh, Loop);
+            return loopStatus;
+        }
+
+
+        public virtual bool Smooth()
+        {
+            int NV = Loop.Vertices.Length;
+
+            double a = MathUtil.Clamp(Alpha, 0, 1);
+            double num_rounds = MathUtil.Clamp(Rounds, 0, 10000);
+
+            for (int round = 0; round < num_rounds; ++round) {
+
+                // compute
+                for (int i = 0; i < NV; ++i) {
+                    int vid = Loop.Vertices[(i + 1) % NV];
+                    Vector3d prev = Mesh.GetVertex(Loop.Vertices[i]);
+                    Vector3d cur = Mesh.GetVertex(vid);
+                    Vector3d next = Mesh.GetVertex(Loop.Vertices[(i + 2) % NV]);
+
+                    Vector3d centroid = (prev + next) * 0.5;
+                    SmoothedPostions[i] = (1 - Alpha) * cur + (Alpha) * centroid;
+                }
+
+                // bake
+                for (int i = 0; i < NV; ++i) {
+                    int vid = Loop.Vertices[(i + 1) % NV];
+                    Mesh.SetVertex(vid, SmoothedPostions[i]);
+                }
+            }
+
+            return true;
+        }
+
+    }
+}

queries/MeshValidation.cs

@@ -8,6 +8,8 @@ public enum ValidationStatus
     {
         Ok,
 
+        NotAVertex,
+
         NotBoundaryVertex,
         NotBoundaryEdge,
 
@@ -19,6 +21,26 @@ public enum ValidationStatus
     public static class MeshValidation
     {
 
+        public static ValidationStatus IsEdgeLoop(DMesh3 mesh, EdgeLoop loop)
+        {
+           int N = loop.Vertices.Length;
+            for ( int i = 0; i < N; ++i ) {
+                if ( ! mesh.IsVertex(loop.Vertices[i]) )
+                    return ValidationStatus.NotAVertex;
+            }
+            for (int i = 0; i < N; ++i) {
+                int a = loop.Vertices[i];
+                int b = loop.Vertices[(i + 1) % N];
+
+                int eid = mesh.FindEdge(a, b);
+                if (eid == DMesh3.InvalidID)
+                    return ValidationStatus.VerticesNotConnectedByEdge;
+            }
+            return ValidationStatus.Ok;
+        }
+
+
+
         public static ValidationStatus IsBoundaryLoop(DMesh3 mesh, EdgeLoop loop)
         {
             int N = loop.Vertices.Length;