The Tonatiuh project aims to create an accurate and easy to use Monte Carlo ray tracer for the optical simulation of solar concentrating systems.Some of design goals are to facilitate the optical simulation of almost any type of solar concentrating system, to exhibit a clean and flexible software architecture that will allow the user to adapt, expand, increase, and modify its functionality with ease, to achieve operating system independence, and to leverage on the use of other well-established state-of-the-art open source libraries, and tools.