public override void LoadAll()
        {
            //version 1
            //new OpenTK.Graphics.ES10.GL().LoadEntryPoints();
            //new OpenTK.Graphics.ES11.GL().LoadEntryPoints();
            //new OpenTK.Graphics.ES20.GL().LoadEntryPoints();


            //version 2
            if (s_bindingBase == null)
            {
                s_bindingBase = new OpenTK.Graphics.ES20.GL();
                s_bindingBase.LoadEntryPoints();
            }
        }