ANR « Modèles Numériques » program is focused on “research on modeling, simulation and optimization for producing numerical virtual worlds”. The AMPERE project is quite compliant to this frame. AMPERE deals with electromagnetic fields simulation within a virtual 3D scene. The proposed activity does not begin from scratch. AMPERE is fully supported by an existing basis among the partners and several R&D studies. The exponential development of new applications in the frame of civilian telecommunication and radiofrequencies domain made crucial the availability of simulation tools for predicting the behavior and the interaction of these systems with the environment. This need is also emphasized by the development of new technologies around phone, WIFI, GNSS and other more specific application that « interfere » with EM. In most of situations, solution of problems, for detecting or communicating, relies on the modeling of the interaction between an EM wave and a complex 3D scene, typically made of 3D natural or man-made objects in their intrinsic environment. When dimensions of objects become large in comparison to the wavelength, asymptotic methods, such as Ray Tracing, are more convenient. Ray Tracing technique, in the frame of electromagnetism, is similar to its equivalent in the Optics domain. This type of technique is well fitted to standard objects such as 3D terrain or 3D simple buildings but is not ideal for more complex objects such as vegetation. In this case, methods such as Monte Carlo Ray Tracing are much more adapted than deterministic Ray Tracing. Partners have a real experience in all these domains. Good results have been obtained by OKTAL-SE and ONERA thanks to the combination of deterministic ray tracing and EM equation formulation. Validation trials have been made by comparison with other simulation methods and by comparison to measurements. The problem is the computation time, especially for cartography application, when there are many receiving points of computation and very complex 3D large scenes. To fight this problem, AMPERE project intends to parallelize the treatments and execute the main part on the GPU of the computation platform. Thanks to GP GPU implementation, we intend to obtain performances well fitted to the demanding industrial applications we target within this project, especially GNSS and mobile telecommunication by satellite. For that purpose, GUIDE structure, a federation of the major players in this domain, support AMPERE as end user. Good results have also been obtained in the frame of Monte Carlo Ray Tracing by IRIT, for visible optics application. We propose to extend these results to EM. For instance, an important challenge is the modeling & simulation of vegetation clutter, made of inhomogeneous media that cannot be modeled using simple surfaces, whose impact on EM signature can be important due to diffusion and scattering phenomena. Clutter is often roughly simulated using simple stochastic models that have poor correlation with the actual 3D scene modeling. AMPERE intends to take advantage of Monte Carlo Ray Tracing in order to solve the EM equations in the frame of complex environments. For instance, in case of forest, Monte Carlo Ray Tracing allows to compute the EM response of the clutter, taking into account its specific 3D characteristics. In this case, AMPERE will simulate the physical laws of reflection and scattering, thanks to a physical based heuristic, performing a coherent waves summation.