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

        private void SubdivideBarycentric()
        {
            // The BCS of a triangle S divides it into six triangles; each part has one vertex v2 at the
            // barycenter of S, another one v1 at the midpoint of some side, and the last one v0 at one
            // of the original vertices.
            int im = this.Positions.Count;
            int ntri = this.TriangleIndices.Count;
            for (int i = 0; i < ntri; i += 3)
            {
                int i0 = this.TriangleIndices[i];
                int i1 = this.TriangleIndices[i + 1];
                int i2 = this.TriangleIndices[i + 2];
                var p0 = this.Positions[i0];
                var p1 = this.Positions[i1];
                var p2 = this.Positions[i2];
                var v01 = p1 - p0;
                var v12 = p2 - p1;
                var v20 = p0 - p2;
                var p01 = p0 + (v01 * 0.5);
                var p12 = p1 + (v12 * 0.5);
                var p20 = p2 + (v20 * 0.5);
                var m = new Point3D((p0.X + p1.X + p2.X) / 3, (p0.Y + p1.Y + p2.Y) / 3, (p0.Z + p1.Z + p2.Z) / 3);

                int i01 = im + 1;
                int i12 = im + 2;
                int i20 = im + 3;

                this.Positions.Add(m);
                this.Positions.Add(p01);
                this.Positions.Add(p12);
                this.Positions.Add(p20);

                if (this.normals != null)
                {
                    var n = this.Normals[i0];
                    this.Normals.Add(n);
                    this.Normals.Add(n);
                    this.Normals.Add(n);
                    this.Normals.Add(n);
                }

                if (this.textureCoordinates != null)
                {
                    var uv0 = this.TextureCoordinates[i0];
                    var uv1 = this.TextureCoordinates[i0 + 1];
                    var uv2 = this.TextureCoordinates[i0 + 2];
                    var t01 = uv1 - uv0;
                    var t12 = uv2 - uv1;
                    var t20 = uv0 - uv2;
                    var u01 = uv0 + (t01 * 0.5);
                    var u12 = uv1 + (t12 * 0.5);
                    var u20 = uv2 + (t20 * 0.5);
                    var uvm = new Point((uv0.X + uv1.X) * 0.5, (uv0.Y + uv1.Y) * 0.5);
                    this.TextureCoordinates.Add(uvm);
                    this.TextureCoordinates.Add(u01);
                    this.TextureCoordinates.Add(u12);
                    this.TextureCoordinates.Add(u20);
                }

                // TriangleIndices[i ] = i0;
                this.TriangleIndices[i + 1] = i01;
                this.TriangleIndices[i + 2] = im;

                this.TriangleIndices.Add(i01);
                this.TriangleIndices.Add(i1);
                this.TriangleIndices.Add(im);

                this.TriangleIndices.Add(i1);
                this.TriangleIndices.Add(i12);
                this.TriangleIndices.Add(im);

                this.TriangleIndices.Add(i12);
                this.TriangleIndices.Add(i2);
                this.TriangleIndices.Add(im);

                this.TriangleIndices.Add(i2);
                this.TriangleIndices.Add(i20);
                this.TriangleIndices.Add(im);

                this.TriangleIndices.Add(i20);
                this.TriangleIndices.Add(i0);
                this.TriangleIndices.Add(im);

                im += 4;
            }
        }