protected override void LoadContent()
        {
            sky = new Sky(sim);
            sky.LoadContent(sim.Content);
            weather = new Weather(sim);
            weather.LoadContent();
            wildlife = new Wildlife(sim);
            wildlife.LoadContent();
            lighting = new Lighting(this);

            PresentationParameters pp = GraphicsDevice.PresentationParameters;
            worldRenderTarget = new RenderTarget2D(GraphicsDevice, pp.BackBufferWidth, pp.BackBufferHeight, 1, SurfaceFormat.Color); 
        }