/// <summary>
        ///
        /// </summary>
        /// <param name="vertices"></param>
        /// <param name="normals"></param>
        /// <param name="indices"></param>
        /// <param name="textures"></param>
        protected void TriangleSubdivide(Point3DCollection vertices,
                                         Vector3DCollection normals,
                                         Int32Collection indices,
                                         PointCollection textures)
        {
            for (int i = 0; i < 3; i++)
            {
                verticesBase[2 - i] = vertices[vertices.Count - 1];
                normalsBase[2 - i]  = normals[vertices.Count - 1];
                texturesBase[2 - i] = textures[vertices.Count - 1];

                vertices.RemoveAt(vertices.Count - 1);
                normals.RemoveAt(normals.Count - 1);
                indices.RemoveAt(indices.Count - 1);
                textures.RemoveAt(textures.Count - 1);
            }

            int indexStart = vertices.Count;

            for (int slice = 0; slice <= Slices; slice++)
            {
                double weight = (double)slice / Slices;

                Point3D vertex1 = Point3DWeight(verticesBase[0], verticesBase[1], weight);
                Point3D vertex2 = Point3DWeight(verticesBase[0], verticesBase[2], weight);

                Vector3D normal1 = Vector3DWeight(normalsBase[0], normalsBase[1], weight);
                Vector3D normal2 = Vector3DWeight(normalsBase[0], normalsBase[2], weight);

                Point texture1 = PointWeight(texturesBase[0], texturesBase[1], weight);
                Point texture2 = PointWeight(texturesBase[0], texturesBase[2], weight);

                for (int i = 0; i <= slice; i++)
                {
                    weight = (double)i / slice;

                    if (Double.IsNaN(weight))
                    {
                        weight = 0;
                    }

                    vertices.Add(Point3DWeight(vertex1, vertex2, weight));
                    normals.Add(Vector3DWeight(normal1, normal2, weight));
                    textures.Add(PointWeight(texture1, texture2, weight));
                }
            }

            for (int slice = 0; slice < Slices; slice++)
            {
                int base1 = (slice + 1) * slice / 2;
                int base2 = base1 + slice + 1;

                for (int i = 0; i <= 2 * slice; i++)
                {
                    int half = i / 2;

                    if ((i & 1) == 0)         // even
                    {
                        indices.Add(indexStart + base1 + half);
                        indices.Add(indexStart + base2 + half);
                        indices.Add(indexStart + base2 + half + 1);
                    }
                    else                    // odd
                    {
                        indices.Add(indexStart + base1 + half);
                        indices.Add(indexStart + base2 + half + 1);
                        indices.Add(indexStart + base1 + half + 1);
                    }
                }
            }
        }