//create camera
     string cameraName = SceneManager.Instance.GetUniqueCameraName( "RenderToTextureExample" );
     camera = SceneManager.Instance.CreateCamera( cameraName );
     camera.Purpose = Camera.Purposes.Special;
     camera.AllowMapCompositorManager = false;

     //add viewport
     viewport = renderTexture.AddViewport( camera );
     viewport.BackgroundColor = new ColorValue( 0, 0, 0, 1 );
     viewport.ShadowsEnabled = false;
     viewport.MaterialScheme = "";