It allows you to control environment, water and airport textures.
REX Essential PLUS OverDrive is a photo-realistic, hi-definition professional graphics package, weather engine and flight planner for Flight Simulator X, Flight Simulator 9 (FS2004), PREPAR3D and X-Plane 9. It allows you to control environment, water and airport textures, as well as lighting effects that are so critical to the enjoyment and immersion within the flight simulator experience.