Pyro is designed to operate in a client/server fashion. This means that a simulator will act as a server, and Pyro will connect onto it. Because of this relationship, it is important to always shutdown Pyro first. The simulator will stop automatically when you exit Pyro.
There are a number of simulators that can be used in conjunction with Pyro. Each simulator has different strengths and weaknesses, so it is important to understand these issues before selecting one to use.
The Pyrobot simulator is the newest addition, and therefore is not as well tested as the others. It is written in python and includes the ability to add lights and light sensors, which is not currently possible in the other simulators described below. Because it is written in python it is the most portable of the simulation options. However, the downside of this is that it can be slow if a complex world with many objects and robots is desired. It can also be run without the GUI window to speed up experiments.
The Stage simulator is designed to work well with multiple robots and can easily handle a complex world with many robots. It is currently undergoing a major upgrade and some aspects are unfinished. For instance, grippers, bumpers, and pan-tilt-zoom cameras are still incomplete. Lights and light sensors are a new addition that will probably be included in the near future. There are also plans to allow it to run without the GUI window.
The Gazebo simulator, like the Stage simulator, is designed to work efficiently for a population of robots. It offers three-dimensional graphics and generates both realistic sensor feedback and physically plausible interactions between objects. It can model sophisticated robot devices such as arms and vision. However, it is very resource hungry, and can be tricky to build. It is still early in its development (version 0.5) and is currenly missing bumpers as well as pan-tilt-zoom cameras.
This has become a popular platform as a result of the many competitions that are based on it. Includes many soccer-related tools and provides communication channels that no other simulations use. The Pyro interface to this simulator is not yet polished, and the simulated vision is still just a sketch of what it should be.
To learn more about these simulators, see the following links: