private void addToContactGraph(Mesh mesh, bool atBoundary, IntPtr graphData)
        {
            CMesh  cmesh = new CMesh();
            String errorMessage;

            if (TopoCreator.RhinoMeshToCMesh(mesh, ref cmesh, false, out errorMessage))
            {
                TopoCreator.addMeshesToContactGraph(graphData, ref cmesh, atBoundary);
            }
            else
            {
                AddRuntimeMessage(GH_RuntimeMessageLevel.Error, errorMessage);
                return;
            }
            Marshal.FreeHGlobal(cmesh.points);
            Marshal.FreeHGlobal(cmesh.faces);
        }