Part III focuses on physical modeling. The aim of this part is to provide you with valuable physical insight so you can make better judgments on what to include in your models and what you can safely leave out without sacrificing physical realism. We cannot and do not attempt to cover all the possible things you might want to simulate. Instead, we cover several typical things you may try to simulate in a game—such as aircraft, boats, and sports balls, among others—in order to give you some insight into their physical nature and into some of the choices you must make when developing suitable models.