added missing code

NewHorizons/Utility/MeshUtilities.cs

@@ -11,7 +11,27 @@ namespace NewHorizons.Utility
     {
         public static Mesh RectangleMeshFromCorners(Vector3[] corners)
         {
-            
+            MVector3[] verts = corners.Select(v => (MVector3)v).ToArray();
+
+            int[] triangles = new int[] {
+                0, 1, 2,
+                1, 3, 2,
+            };
+
+            MVector3[] normals = new MVector3[verts.Length];
+            for (int i = 0; i<verts.Length; i++) normals[i] = new Vector3(0, 0, 1);
+
+            MVector2[] uv = new MVector2[] {
+                new Vector2(0, 0), new Vector2(0, 1),
+                new Vector2(1, 0), new Vector2(1, 1),
+            };
+
+            MVector2[] uv2 = new MVector2[] {
+                new Vector2(0, 0), new Vector2(0, 1),
+                new Vector2(1, 0), new Vector2(1, 1),
+            };
+
+            return new MMesh(verts, triangles, normals, uv, uv2);
         }
     }
 }