static ConnectFaceRebuildData InsertVertices(Face face, List <WingedEdge> edges, List <Vertex> vertices)
        {
            List <Edge>    perimeter        = WingedEdge.SortEdgesByAdjacency(face);
            List <Vertex>  n_vertices       = new List <Vertex>();
            List <int>     newVertexIndexes = new List <int>();
            HashSet <Edge> affected         = new HashSet <Edge>(edges.Select(x => x.edge.local));

            for (int i = 0; i < perimeter.Count; i++)
            {
                n_vertices.Add(vertices[perimeter[i].a]);

                if (affected.Contains(perimeter[i]))
                {
                    newVertexIndexes.Add(n_vertices.Count);
                    n_vertices.Add(Vertex.Mix(vertices[perimeter[i].a], vertices[perimeter[i].b], .5f));
                }
            }

            FaceRebuildData res = AppendElements.FaceWithVertices(n_vertices, false);

            res.face.textureGroup   = face.textureGroup;
            res.face.uv             = new AutoUnwrapSettings(face.uv);
            res.face.smoothingGroup = face.smoothingGroup;
            res.face.manualUV       = face.manualUV;
            res.face.submeshIndex   = face.submeshIndex;

            return(new ConnectFaceRebuildData(res, newVertexIndexes));
        }
示例#2
0
        /// <summary>
        /// Insert a new vertex at the center of a face and connect the center of all edges to it.
        /// </summary>
        /// <param name="face"></param>
        /// <param name="edges"></param>
        /// <param name="vertices"></param>
        /// <returns></returns>
        static List <ConnectFaceRebuildData> ConnectEdgesInFace(
            Face face,
            List <WingedEdge> edges,
            List <Vertex> vertices)
        {
            List <Edge> perimeter  = WingedEdge.SortEdgesByAdjacency(face);
            int         splitCount = edges.Count;

            Vertex centroid = Vertex.Average(vertices, face.distinctIndexesInternal);

            List <List <Vertex> > n_vertices = ArrayUtility.Fill <List <Vertex> >(x => { return(new List <Vertex>()); }, splitCount);
            List <List <int> >    n_indexes  = ArrayUtility.Fill <List <int> >(x => { return(new List <int>()); }, splitCount);

            HashSet <Edge> edgesToSplit = new HashSet <Edge>(edges.Select(x => x.edge.local));

            int index = 0;

            // creates two new polygon perimeter lines by stepping the current face perimeter and inserting new vertices where edges match
            for (int i = 0; i < perimeter.Count; i++)
            {
                n_vertices[index % splitCount].Add(vertices[perimeter[i].a]);

                if (edgesToSplit.Contains(perimeter[i]))
                {
                    Vertex mix = Vertex.Mix(vertices[perimeter[i].a], vertices[perimeter[i].b], .5f);

                    // split current poly line
                    n_indexes[index].Add(n_vertices[index].Count);
                    n_vertices[index].Add(mix);

                    // add the centroid vertex
                    n_indexes[index].Add(n_vertices[index].Count);
                    n_vertices[index].Add(centroid);

                    // advance the poly line index
                    index = (index + 1) % splitCount;

                    // then add the edge center vertex and move on
                    n_vertices[index].Add(mix);
                }
            }

            List <ConnectFaceRebuildData> faces = new List <ConnectFaceRebuildData>();

            for (int i = 0; i < n_vertices.Count; i++)
            {
                FaceRebuildData f = AppendElements.FaceWithVertices(n_vertices[i], false);
                if (f == null)
                {
                    faces.Clear();
                    return(null);
                }
                faces.Add(new ConnectFaceRebuildData(f, n_indexes[i]));
            }

            return(faces);
        }
示例#3
0
        /// <summary>
        /// Accepts a face and set of edges to split on.
        /// </summary>
        /// <param name="face"></param>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <param name="vertices"></param>
        /// <returns></returns>
        static List <ConnectFaceRebuildData> ConnectEdgesInFace(
            Face face,
            WingedEdge a,
            WingedEdge b,
            List <Vertex> vertices)
        {
            List <Edge> perimeter = WingedEdge.SortEdgesByAdjacency(face);

            List <Vertex>[] n_vertices = new List <Vertex>[2]
            {
                new List <Vertex>(),
                new List <Vertex>()
            };

            List <int>[] n_indexes = new List <int>[2]
            {
                new List <int>(),
                new List <int>()
            };

            int index = 0;

            // creates two new polygon perimeter lines by stepping the current face perimeter and inserting new vertices where edges match
            for (int i = 0; i < perimeter.Count; i++)
            {
                n_vertices[index % 2].Add(vertices[perimeter[i].a]);

                if (perimeter[i].Equals(a.edge.local) || perimeter[i].Equals(b.edge.local))
                {
                    Vertex mix = Vertex.Mix(vertices[perimeter[i].a], vertices[perimeter[i].b], .5f);

                    n_indexes[index % 2].Add(n_vertices[index % 2].Count);
                    n_vertices[index % 2].Add(mix);
                    index++;
                    n_indexes[index % 2].Add(n_vertices[index % 2].Count);
                    n_vertices[index % 2].Add(mix);
                }
            }

            List <ConnectFaceRebuildData> faces = new List <ConnectFaceRebuildData>();

            for (int i = 0; i < n_vertices.Length; i++)
            {
                FaceRebuildData f = AppendElements.FaceWithVertices(n_vertices[i], false);
                faces.Add(new ConnectFaceRebuildData(f, n_indexes[i]));
            }

            return(faces);
        }
        /// <summary>
        /// Insert a number of new points to each edge. Points are evenly spaced out along the edge.
        /// </summary>
        /// <param name="mesh">The source mesh.</param>
        /// <param name="edges">The edges to split with points.</param>
        /// <param name="count">The number of new points to insert. Must be greater than 0.</param>
        /// <returns>The new edges created by inserting points.</returns>
        public static List <Edge> AppendVerticesToEdge(this ProBuilderMesh mesh, IList <Edge> edges, int count)
        {
            if (mesh == null)
            {
                throw new ArgumentNullException("mesh");
            }

            if (edges == null)
            {
                throw new ArgumentNullException("edges");
            }

            if (count < 1 || count > 512)
            {
                Log.Error("New edge vertex count is less than 1 or greater than 512.");
                return(null);
            }

            List <Vertex>         vertices        = new List <Vertex>(mesh.GetVertices());
            Dictionary <int, int> lookup          = mesh.sharedVertexLookup;
            Dictionary <int, int> lookupUV        = mesh.sharedTextureLookup;
            List <int>            indexesToDelete = new List <int>();
            IEnumerable <Edge>    commonEdges     = EdgeUtility.GetSharedVertexHandleEdges(mesh, edges);
            List <Edge>           distinctEdges   = commonEdges.Distinct().ToList();

            Dictionary <Face, FaceRebuildData> modifiedFaces = new Dictionary <Face, FaceRebuildData>();

            int originalSharedIndexesCount = lookup.Count();
            int sharedIndexesCount         = originalSharedIndexesCount;

            foreach (Edge edge in distinctEdges)
            {
                Edge localEdge = EdgeUtility.GetEdgeWithSharedVertexHandles(mesh, edge);

                // Generate the new vertices that will be inserted on this edge
                List <Vertex> verticesToAppend = new List <Vertex>(count);

                for (int i = 0; i < count; i++)
                {
                    verticesToAppend.Add(Vertex.Mix(vertices[localEdge.a], vertices[localEdge.b],
                                                    (i + 1) / ((float)count + 1)));
                }

                List <SimpleTuple <Face, Edge> > adjacentFaces = ElementSelection.GetNeighborFaces(mesh, localEdge);
                Edge edgeLookUp = new Edge(lookup[localEdge.a], lookup[localEdge.b]);
                Edge e          = new Edge();

                // foreach face attached to common edge, append vertices
                foreach (SimpleTuple <Face, Edge> tup in adjacentFaces)
                {
                    Face face = tup.item1;

                    FaceRebuildData data;

                    if (!modifiedFaces.TryGetValue(face, out data))
                    {
                        data      = new FaceRebuildData();
                        data.face = new Face(new int[0], face.submeshIndex, new AutoUnwrapSettings(face.uv),
                                             face.smoothingGroup, face.textureGroup, -1, face.manualUV);
                        data.vertices =
                            new List <Vertex>(ArrayUtility.ValuesWithIndexes(vertices, face.distinctIndexesInternal));
                        data.sharedIndexes   = new List <int>();
                        data.sharedIndexesUV = new List <int>();

                        foreach (int i in face.distinctIndexesInternal)
                        {
                            int shared;

                            if (lookup.TryGetValue(i, out shared))
                            {
                                data.sharedIndexes.Add(shared);
                            }

                            if (lookupUV.TryGetValue(i, out shared))
                            {
                                data.sharedIndexesUV.Add(shared);
                            }
                        }

                        indexesToDelete.AddRange(face.distinctIndexesInternal);

                        modifiedFaces.Add(face, data);

                        //Ordering vertices in the new face
                        List <Vertex> orderedVertices        = new List <Vertex>();
                        List <int>    orderedSharedIndexes   = new List <int>();
                        List <int>    orderedSharedUVIndexes = new List <int>();
                        List <Edge>   peripheralEdges        = WingedEdge.SortEdgesByAdjacency(face);

                        for (int i = 0; i < peripheralEdges.Count; i++)
                        {
                            e.a = peripheralEdges[i].a;
                            e.b = peripheralEdges[i].b;

                            orderedVertices.Add(vertices[e.a]);

                            int shared;
                            if (lookup.TryGetValue(e.a, out shared))
                            {
                                orderedSharedIndexes.Add(shared);
                            }

                            if (lookupUV.TryGetValue(i, out shared))
                            {
                                data.sharedIndexesUV.Add(shared);
                            }

                            if (edgeLookUp.a == lookup[e.a] && edgeLookUp.b == lookup[e.b])
                            {
                                for (int j = 0; j < count; j++)
                                {
                                    orderedVertices.Add(verticesToAppend[j]);
                                    orderedSharedIndexes.Add(sharedIndexesCount + j);
                                    orderedSharedUVIndexes.Add(-1);
                                }
                            }
                            else if (edgeLookUp.a == lookup[e.b] && edgeLookUp.b == lookup[e.a])
                            {
                                for (int j = count - 1; j >= 0; j--)
                                {
                                    orderedVertices.Add(verticesToAppend[j]);
                                    orderedSharedIndexes.Add(sharedIndexesCount + j);
                                    orderedSharedUVIndexes.Add(-1);
                                }
                            }
                        }

                        data.vertices        = orderedVertices;
                        data.sharedIndexes   = orderedSharedIndexes;
                        data.sharedIndexesUV = orderedSharedUVIndexes;
                    }
                    else
                    {
                        //Get ordered vertices in the existing face and add new ones
                        List <Vertex> orderedVertices        = data.vertices;
                        List <int>    orderedSharedIndexes   = data.sharedIndexes;
                        List <int>    orderedSharedUVIndexes = data.sharedIndexesUV;

                        for (int i = 0; i < orderedVertices.Count; i++)
                        {
                            Vertex edgeStart      = orderedVertices[i];
                            int    edgeStartIndex = vertices.IndexOf(edgeStart);

                            Vertex edgeEnd      = orderedVertices[(i + 1) % orderedVertices.Count];
                            int    edgeEndIndex = vertices.IndexOf(edgeEnd);

                            if (edgeStartIndex == -1 || edgeEndIndex == -1)
                            {
                                continue;
                            }

                            if (lookup[edgeStartIndex] == lookup[localEdge.a] &&
                                lookup[edgeEndIndex] == lookup[localEdge.b])
                            {
                                orderedVertices.InsertRange(i + 1, verticesToAppend);
                                for (int j = 0; j < count; j++)
                                {
                                    orderedSharedIndexes.Insert(i + j + 1, sharedIndexesCount + j);
                                    orderedSharedUVIndexes.Add(-1);
                                }
                            }
                            else if (lookup[edgeStartIndex] == lookup[localEdge.b] &&
                                     lookup[edgeEndIndex] == lookup[localEdge.a])
                            {
                                verticesToAppend.Reverse();
                                orderedVertices.InsertRange(i + 1, verticesToAppend);
                                for (int j = count - 1; j >= 0; j--)
                                {
                                    orderedSharedIndexes.Insert(i + 1, sharedIndexesCount + j);
                                    orderedSharedUVIndexes.Add(-1);
                                }
                            }
                        }

                        data.vertices        = orderedVertices;
                        data.sharedIndexes   = orderedSharedIndexes;
                        data.sharedIndexesUV = orderedSharedUVIndexes;
                    }
                }

                sharedIndexesCount += count;
            }

            // now apply the changes
            List <Face>            dic_face      = modifiedFaces.Keys.ToList();
            List <FaceRebuildData> dic_data      = modifiedFaces.Values.ToList();
            List <EdgeLookup>      appendedEdges = new List <EdgeLookup>();

            for (int i = 0; i < dic_face.Count; i++)
            {
                Face            face = dic_face[i];
                FaceRebuildData data = dic_data[i];

                int vertexCount = vertices.Count;
                // triangulate and set new face indexes to end of current vertex list
                List <int> triangles;

                if (Triangulation.TriangulateVertices(data.vertices, out triangles, false))
                {
                    data.face = new Face(triangles);
                }
                else
                {
                    continue;
                }

                data.face.ShiftIndexes(vertexCount);
                face.CopyFrom(data.face);

                for (int n = 0; n < data.vertices.Count; n++)
                {
                    lookup.Add(vertexCount + n, data.sharedIndexes[n]);
                }

                if (data.sharedIndexesUV.Count == data.vertices.Count)
                {
                    for (int n = 0; n < data.vertices.Count; n++)
                    {
                        lookupUV.Add(vertexCount + n, data.sharedIndexesUV[n]);
                    }
                }

                vertices.AddRange(data.vertices);

                foreach (Edge e in face.edgesInternal)
                {
                    EdgeLookup el = new EdgeLookup(new Edge(lookup[e.a], lookup[e.b]), e);

                    if (el.common.a >= originalSharedIndexesCount || el.common.b >= originalSharedIndexesCount)
                    {
                        appendedEdges.Add(el);
                    }
                }
            }

            indexesToDelete = indexesToDelete.Distinct().ToList();
            int delCount = indexesToDelete.Count;

            var newEdges = appendedEdges.Distinct().Select(x => x.local - delCount).ToList();

            mesh.SetVertices(vertices);
            mesh.SetSharedVertices(lookup);
            mesh.SetSharedTextures(lookupUV);
            mesh.DeleteVertices(indexesToDelete);

            return(newEdges);
        }
        /// <summary>
        /// Add a set of points to a face and retriangulate. Points are added to the nearest edge.
        /// </summary>
        /// <param name="mesh">The source mesh.</param>
        /// <param name="face">The face to append points to.</param>
        /// <param name="points">Points to added to the face.</param>
        /// <returns>The face created by appending the points.</returns>
        public static Face AppendVerticesToFace(this ProBuilderMesh mesh, Face face, Vector3[] points)
        {
            if (mesh == null)
            {
                throw new ArgumentNullException("mesh");
            }

            if (face == null)
            {
                throw new ArgumentNullException("face");
            }

            if (points == null)
            {
                throw new ArgumentNullException("points");
            }

            List <Vertex>         vertices = mesh.GetVertices().ToList();
            List <Face>           faces    = new List <Face>(mesh.facesInternal);
            Dictionary <int, int> lookup   = mesh.sharedVertexLookup;
            Dictionary <int, int> lookupUV = null;

            if (mesh.sharedTextures != null)
            {
                lookupUV = new Dictionary <int, int>();
                SharedVertex.GetSharedVertexLookup(mesh.sharedTextures, lookupUV);
            }

            List <Edge> wound = WingedEdge.SortEdgesByAdjacency(face);

            List <Vertex> n_vertices = new List <Vertex>();
            List <int>    n_shared   = new List <int>();
            List <int>    n_sharedUV = lookupUV != null ? new List <int>() : null;

            for (int i = 0; i < wound.Count; i++)
            {
                n_vertices.Add(vertices[wound[i].a]);
                n_shared.Add(lookup[wound[i].a]);

                if (lookupUV != null)
                {
                    int uv;

                    if (lookupUV.TryGetValue(wound[i].a, out uv))
                    {
                        n_sharedUV.Add(uv);
                    }
                    else
                    {
                        n_sharedUV.Add(-1);
                    }
                }
            }

            // now insert the new points on the nearest edge
            for (int i = 0; i < points.Length; i++)
            {
                int     index = -1;
                float   best  = Mathf.Infinity;
                Vector3 p     = points[i];
                int     vc    = n_vertices.Count;

                for (int n = 0; n < vc; n++)
                {
                    Vector3 v = n_vertices[n].position;
                    Vector3 w = n_vertices[(n + 1) % vc].position;

                    float dist = Math.DistancePointLineSegment(p, v, w);

                    if (dist < best)
                    {
                        best  = dist;
                        index = n;
                    }
                }

                Vertex left = n_vertices[index], right = n_vertices[(index + 1) % vc];

                float x = (p - left.position).sqrMagnitude;
                float y = (p - right.position).sqrMagnitude;

                Vertex insert = Vertex.Mix(left, right, x / (x + y));

                n_vertices.Insert((index + 1) % vc, insert);
                n_shared.Insert((index + 1) % vc, -1);
                if (n_sharedUV != null)
                {
                    n_sharedUV.Insert((index + 1) % vc, -1);
                }
            }

            List <int> triangles;

            try
            {
                Triangulation.TriangulateVertices(n_vertices, out triangles, false);
            }
            catch
            {
                Debug.Log("Failed triangulating face after appending vertices.");
                return(null);
            }

            FaceRebuildData data = new FaceRebuildData();

            data.face = new Face(triangles.ToArray(), face.submeshIndex, new AutoUnwrapSettings(face.uv),
                                 face.smoothingGroup, face.textureGroup, -1, face.manualUV);
            data.vertices        = n_vertices;
            data.sharedIndexes   = n_shared;
            data.sharedIndexesUV = n_sharedUV;

            FaceRebuildData.Apply(new List <FaceRebuildData>()
            {
                data
            },
                                  vertices,
                                  faces,
                                  lookup,
                                  lookupUV);

            var newFace = data.face;

            mesh.SetVertices(vertices);
            mesh.faces = faces;
            mesh.SetSharedVertices(lookup);
            mesh.SetSharedTextures(lookupUV);

            // check old normal and make sure this new face is pointing the same direction
            Vector3 oldNrm = Math.Normal(mesh, face);
            Vector3 newNrm = Math.Normal(mesh, newFace);

            if (Vector3.Dot(oldNrm, newNrm) < 0)
            {
                newFace.Reverse();
            }

            mesh.DeleteFace(face);

            return(newFace);
        }
示例#6
0
        static List <ConnectFaceRebuildData> ConnectIndexesPerFace(
            Face face,
            List <int> indexes,
            List <Vertex> vertices,
            Dictionary <int, int> lookup,
            int sharedIndexOffset)
        {
            if (indexes.Count < 3)
            {
                return(null);
            }

            List <Edge> perimeter = WingedEdge.SortEdgesByAdjacency(face);

            int splitCount = indexes.Count;

            List <List <Vertex> > n_vertices      = ArrayUtility.Fill <List <Vertex> >(x => { return(new List <Vertex>()); }, splitCount);
            List <List <int> >    n_sharedIndexes = ArrayUtility.Fill <List <int> >(x => { return(new List <int>()); }, splitCount);
            List <List <int> >    n_indexes       = ArrayUtility.Fill <List <int> >(x => { return(new List <int>()); }, splitCount);

            Vertex  center = Vertex.Average(vertices, indexes);
            Vector3 nrm    = Math.Normal(vertices, face.indexesInternal);

            int index = 0;

            for (int i = 0; i < perimeter.Count; i++)
            {
                int cur = perimeter[i].a;

                n_vertices[index].Add(vertices[cur]);
                n_sharedIndexes[index].Add(lookup[cur]);

                if (indexes.Contains(cur))
                {
                    n_indexes[index].Add(n_vertices[index].Count);
                    n_vertices[index].Add(center);
                    n_sharedIndexes[index].Add(sharedIndexOffset);

                    index = (index + 1) % splitCount;

                    n_indexes[index].Add(n_vertices[index].Count);
                    n_vertices[index].Add(vertices[cur]);
                    n_sharedIndexes[index].Add(lookup[cur]);
                }
            }

            List <ConnectFaceRebuildData> faces = new List <ConnectFaceRebuildData>();

            for (int i = 0; i < n_vertices.Count; i++)
            {
                if (n_vertices[i].Count < 3)
                {
                    continue;
                }

                FaceRebuildData f = AppendElements.FaceWithVertices(n_vertices[i], false);
                f.sharedIndexes = n_sharedIndexes[i];

                Vector3 fn = Math.Normal(n_vertices[i], f.face.indexesInternal);

                if (Vector3.Dot(nrm, fn) < 0)
                {
                    f.face.Reverse();
                }

                faces.Add(new ConnectFaceRebuildData(f, n_indexes[i]));
            }

            return(faces);
        }
示例#7
0
        static List <ConnectFaceRebuildData> ConnectIndexesPerFace(
            Face face,
            int a,
            int b,
            List <Vertex> vertices,
            Dictionary <int, int> lookup)
        {
            List <Edge> perimeter = WingedEdge.SortEdgesByAdjacency(face);

            List <Vertex>[] n_vertices = new List <Vertex>[] {
                new List <Vertex>(),
                new List <Vertex>()
            };

            List <int>[] n_sharedIndexes = new List <int>[] {
                new List <int>(),
                new List <int>()
            };

            List <int>[] n_indexes = new List <int>[] {
                new List <int>(),
                new List <int>()
            };

            int index = 0;

            for (int i = 0; i < perimeter.Count; i++)
            {
                // trying to connect two vertices that are already connected
                if (perimeter[i].Contains(a) && perimeter[i].Contains(b))
                {
                    return(null);
                }

                int cur = perimeter[i].a;

                n_vertices[index].Add(vertices[cur]);
                n_sharedIndexes[index].Add(lookup[cur]);

                if (cur == a || cur == b)
                {
                    index = (index + 1) % 2;

                    n_indexes[index].Add(n_vertices[index].Count);
                    n_vertices[index].Add(vertices[cur]);
                    n_sharedIndexes[index].Add(lookup[cur]);
                }
            }

            List <ConnectFaceRebuildData> faces = new List <ConnectFaceRebuildData>();
            Vector3 nrm = Math.Normal(vertices, face.indexesInternal);

            for (int i = 0; i < n_vertices.Length; i++)
            {
                FaceRebuildData f = AppendElements.FaceWithVertices(n_vertices[i], false);
                f.sharedIndexes = n_sharedIndexes[i];

                Vector3 fn = Math.Normal(n_vertices[i], f.face.indexesInternal);

                if (Vector3.Dot(nrm, fn) < 0)
                {
                    f.face.Reverse();
                }

                faces.Add(new ConnectFaceRebuildData(f, n_indexes[i]));
            }

            return(faces);
        }
        /// <summary>
        /// Split a common index on a face into two vertices and slide each vertex backwards along it's feeding edge by distance.
        /// This method does not perform any input validation, so make sure edgeAndCommonIndex is distinct and all winged edges belong
        /// to the same face.
        ///<pre>
        /// `appendedVertices` is common index and a list of the new face indexes it was split into.
        ///
        /// _ _ _ _          _ _ _
        /// |              /
        /// |         ->   |
        /// |              |
        /// </pre>
        /// </summary>
        /// <param name="vertices"></param>
        /// <param name="edgeAndCommonIndex"></param>
        /// <param name="distance"></param>
        /// <param name="appendedVertices"></param>
        /// <returns></returns>
        internal static FaceRebuildData ExplodeVertex(
            IList <Vertex> vertices,
            IList <SimpleTuple <WingedEdge, int> > edgeAndCommonIndex,
            float distance,
            out Dictionary <int, List <int> > appendedVertices)
        {
            Face        face      = edgeAndCommonIndex.FirstOrDefault().item1.face;
            List <Edge> perimeter = WingedEdge.SortEdgesByAdjacency(face);

            appendedVertices = new Dictionary <int, List <int> >();
            Vector3 oldNormal = Math.Normal(vertices, face.indexesInternal);

            // store local and common index of split points
            Dictionary <int, int> toSplit = new Dictionary <int, int>();

            foreach (SimpleTuple <WingedEdge, int> v in edgeAndCommonIndex)
            {
                if (v.item2 == v.item1.edge.common.a)
                {
                    toSplit.Add(v.item1.edge.local.a, v.item2);
                }
                else
                {
                    toSplit.Add(v.item1.edge.local.b, v.item2);
                }
            }

            int           pc         = perimeter.Count;
            List <Vertex> n_vertices = new List <Vertex>();

            for (int i = 0; i < pc; i++)
            {
                int index = perimeter[i].b;

                // split this index into two
                if (toSplit.ContainsKey(index))
                {
                    // a --- b --- c
                    Vertex a = vertices[perimeter[i].a];
                    Vertex b = vertices[perimeter[i].b];
                    Vertex c = vertices[perimeter[(i + 1) % pc].b];

                    Vertex leading_dir   = a - b;
                    Vertex following_dir = c - b;
                    leading_dir.Normalize();
                    following_dir.Normalize();

                    Vertex leading_insert   = vertices[index] + leading_dir * distance;
                    Vertex following_insert = vertices[index] + following_dir * distance;

                    appendedVertices.AddOrAppend(toSplit[index], n_vertices.Count);
                    n_vertices.Add(leading_insert);

                    appendedVertices.AddOrAppend(toSplit[index], n_vertices.Count);
                    n_vertices.Add(following_insert);
                }
                else
                {
                    n_vertices.Add(vertices[index]);
                }
            }

            List <int> triangles;

            if (Triangulation.TriangulateVertices(n_vertices, out triangles, false))
            {
                FaceRebuildData data = new FaceRebuildData();
                data.vertices = n_vertices;
                data.face     = new Face(face);

                Vector3 newNormal = Math.Normal(n_vertices, triangles);

                if (Vector3.Dot(oldNormal, newNormal) < 0f)
                {
                    triangles.Reverse();
                }

                data.face.indexesInternal = triangles.ToArray();

                return(data);
            }

            return(null);
        }