/*
         * Create the VBO for the border
         * */
        void CreateBorderVBO()
        {
            borderVBO = new VertexBufferObject();
            List <TriangleEdge> borderEdges = mesh.GetBorder();
            Color4 borderColor = Color4.Pink;
            List <RenderVertex> renderVertices = new List <RenderVertex>();

            for (int i = 0; i < borderEdges.Count; i++)
            {
                TriangleEdge edge = borderEdges[i];
                Vector3      a    = mesh.GetVertex(edge.A);
                Vector3      b    = mesh.GetVertex(edge.B);
                renderVertices.Add(new RenderVertex(a, new Vector3(0, 1, 0), borderColor));
                renderVertices.Add(new RenderVertex(b, new Vector3(0, 1, 0), borderColor));
            }
            borderVBO.Setup(renderVertices, PrimitiveType.Lines);
        }
        /*
         * Vreate the VBO for the normals
         * */
        void CreateNormalsVBO()
        {
            normalsVBO = new VertexBufferObject();
            List <RenderVertex> renderVertices = new List <RenderVertex>();
            float  scale       = 0.05f;
            Color4 normalColor = Color4.DarkGray;

            for (int triangleIndex = 0; triangleIndex < mesh.GetNumberOfTriangles(); triangleIndex++)
            {
                Triangle t        = mesh.GetTriangle(triangleIndex);
                Vector3  centroid = Vector3.Multiply(
                    Vector3.Add(mesh.GetVertex(t.GetVertexIndex(0)),
                                Vector3.Add(mesh.GetVertex(t.GetVertexIndex(1)), mesh.GetVertex(t.GetVertexIndex(2)))), 1.0f / 3.0f);
                Vector3 centroid2normal = Vector3.Add(centroid, Vector3.Multiply(t.Normal, scale));
                renderVertices.Add(new RenderVertex(centroid, t.Normal, normalColor));
                renderVertices.Add(new RenderVertex(centroid2normal, t.Normal, normalColor));
            }
            normalsVBO.Setup(renderVertices, PrimitiveType.Lines);
        }