The Tonatiuh project aims to create an open source, cutting-edge, accurate, and easy to use Monte Carlo ray tracer for the optical simulation of solar concentrating systems. It intends to advance the state-of-the-art of the simulation tools available for the design and analysis of solar concentrating systems, and to make those tools freely available to anyone interested in using and improving them. Some of the most relevant design goals of Tonatiuh are: * To develop a robust theoretical foundation that will facilitate the optical simulation of almost any type of solar concentrating systems. * To exhibit a clean and flexible software architecture, that will allow the user to adapt, expand, increase, and modify its functionalities with ease. * To achieve operating system independence at source level, and run on all major platforms with none, or minor, modifications to its source code. * To provide the users with an advanced and easy-of-use Graphic User Interface (GUI). Program Features:¶ The use of extended Open Inventor files to represent the "scene" (i.e. the solar concentrating system, the sunlight model, etc.). An advance and easy-to-use GUI providing: * 3D and tree views of the "scene" to simulate. * Handlers and manipulators to modify and query scene objects using 3D views. * Interface elements to manage the undo and redo of user actions. * Interface elements to define de type of Monte Carlo ray tracing to execute. A pervasive plugin architecture which allos the user to: * Add new sunlight models. * Add new geometric surfaces. * Add new reflective materials. * (planned) Add new refractive materials. * (planned) Add new photon map and other results analyzers, and post-processors. * (planned) Add new spectrum models.