protected override void OnFrameStarted( object source, FrameEventArgs evt )
{
base.OnFrameStarted( source, evt );
if ( evt.StopRendering )
return;
float mouseX = input.AbsoluteMouseX / (float)window.Width;
float mouseY = input.AbsoluteMouseY / (float)window.Height;
Ray ray = camera.GetCameraToViewportRay( mouseX, mouseY );
headNode.ShowBoundingBox = ray.Intersects( headNode.WorldBoundingSphere ).Hit;
debugText = String.Format( " Mouse X:{0}, Y:{1}", mouseX, mouseY );
}