public void BeforeRender2D(Viewport2D viewport)
{
_offset = 3 / (double)viewport.Zoom;
_fadeDistance = 200 / (double)viewport.Zoom;
var mp = viewport.PointToClient(Control.MousePosition);
_mousePos = viewport.ScreenToWorld(new Coordinate(mp.X, viewport.Height - mp.Y, 0));
GL.Enable(EnableCap.LineSmooth);
GL.Begin(BeginMode.Lines);
}