public IRenderingSurface GetRenderingSurface(IntPtr windowID, int width, int height)
		{
			if (_surface == null)
				_surface = new VtkRenderingSurface(windowID);
			else
				_surface.WindowID = windowID;

			_surface.ClientRectangle = new Rectangle(0, 0, width, height);

			return _surface;
		}
        public IRenderingSurface CreateRenderingSurface(IntPtr windowID, int width, int height, RenderingSurfaceType type)
        {
            if (_surface == null)
            {
                _surface = new VtkRenderingSurface(windowID);
            }
            else
            {
                _surface.WindowID = windowID;
            }

            _surface.ClientRectangle = new Rectangle(0, 0, width, height);

            return(_surface);
        }