HelixToolkit.Wpf.MeshBuilder.AddTriangleFan C# (CSharp) Method

        public void AddTriangleFan(
            IList<Point3D> fanPositions, IList<Vector3D> fanNormals = null, IList<Point> fanTextureCoordinates = null)
        {
            if (this.positions == null)
            {
                throw new ArgumentNullException("fanPositions");
            }

            if (this.normals != null && this.normals == null)
            {
                throw new ArgumentNullException("fanNormals");
            }

            if (this.textureCoordinates != null && this.textureCoordinates == null)
            {
                throw new ArgumentNullException("fanTextureCoordinates");
            }

            int index0 = this.positions.Count;
            foreach (var p in fanPositions)
            {
                this.positions.Add(p);
            }

            if (this.textureCoordinates != null && fanTextureCoordinates != null)
            {
                foreach (var tc in fanTextureCoordinates)
                {
                    this.textureCoordinates.Add(tc);
                }
            }

            if (this.normals != null && fanNormals != null)
            {
                foreach (var n in fanNormals)
                {
                    this.normals.Add(n);
                }
            }

            int indexEnd = this.positions.Count;
            for (int i = index0; i + 2 < indexEnd; i++)
            {
                this.triangleIndices.Add(index0);
                this.triangleIndices.Add(i + 1);
                this.triangleIndices.Add(i + 2);
            }
        }

        /// <summary>
        /// Do the tessellation and return the <see cref="MeshGeometry3D"/> .
        /// </summary>
        /// <returns>
        /// A triangular mesh geometry.
        /// </returns>
        protected override MeshGeometry3D Tessellate()
        {
            if (this.Path == null || this.Path.Count < 2)
            {
                return null;
            }

            // See also "The GLE Tubing and Extrusion Library":
            // http://linas.org/gle/
            // http://sharpmap.codeplex.com/Thread/View.aspx?ThreadId=18864
            var builder = new MeshBuilder(false, this.TextureCoordinates != null);

            var sectionXAxis = this.SectionXAxis;
            if (sectionXAxis.Length < 1e-6)
            {
                sectionXAxis = new Vector3D(1, 0, 0);
            }

            var forward = this.Path[1] - this.Path[0];
            var up = Vector3D.CrossProduct(forward, sectionXAxis);
            if (up.LengthSquared < 1e-6)
            {
                sectionXAxis = forward.FindAnyPerpendicular();
            }

            builder.AddTube(
                this.Path,
                this.Angles,
                this.TextureCoordinates,
                this.Diameters,
                this.Section,
                sectionXAxis,
                this.IsPathClosed,
                this.IsSectionClosed);

            // Add Caps if wanted and needed
            if (this.AddCaps && !this.IsPathClosed && builder.Positions.Count >= Section.Count)
            {
                var sCount = Section.Count;
                var normals = new Vector3D[sCount];
                var vertices = new Point3D[sCount];
                var pCount = Path.Count;

                //Add back cap
                var circleBack = builder.Positions.Skip(builder.Positions.Count - sCount).Take(sCount).ToArray();
                var normal = Path[pCount - 1] - Path[pCount - 2];
                normal.Normalize();
                for (int i = 0; i < normals.Length; ++i)
                {
                    normals[i] = normal;
                }
                builder.AddTriangleFan(circleBack, normals);
                //Add front cap
                var circleFront = builder.Positions.Take(sCount).ToArray();
                normal = Path[0] - Path[1];
                normal.Normalize();

                for (int i = 0; i < normals.Length; ++i)
                {
                    normals[i] = normal;
                }
                builder.AddTriangleFan(circleFront, normals);
            }

            return builder.ToMesh();
        }