1. A method for modeling interactions within a system between at least one wave and at least two objects, a surface of each object defining an interface between at least two media, wherein this method comprises the following steps: a user entering into a computer a set of elementary characteristic functions for a computer model that correspond to a field of the interactions, the user entering into the computer model physical properties of each medium in the system, the user entering into the computer model a geometrical structure of each object of the system and the computer modeling the geometrical structure as a mesh, the computer positioning at least one test point at a surface of each element of the mesh, the user defining at each test point, at least one test quantity for each medium, the user associating at least one elementary point source with a side of each mesh element, the user positioning the objects in the computer model with respect to one another within a volume in the computer model, the user associating in the computer model the physical properties of a one of the media with the volumes bounded by the objects, the user entering into the computer model a type of boundary condition for each interface, the computer constructing a global matrix for the interactions between the objects, the global matrix being formed from at least one matrix block characterizing the interactions between the objects taken in pairs, the interactions based on a propagation of the wave in the medium of the objects using the characteristic elementary functions chosen, the global matrix comprising, at the most, as many blocks as there are possible combinations between all the objects taken in pairs, a content of each block comprising the defined test quantity at the test points of the respective pair of objects, and on the geometrical configuration of each pair of objects, inverting the global matrix, the computer multiplying the inverted matrix by a column matrix containing values for boundary conditions imposed by the user, and, zeros for intrinsic boundary conditions, to obtain a column matrix that contains values of all of the elementary point sources, the computer calculating at points in a display space, physical quantities representing the interactions between the at least one wave and at least two objects, based on the values of all of the elementary point sources, wherein the physical quantities are at least one of electromagnetic, magnetic, acoustic, optical, geophysical, Foucault currents, or thermal quantities, and the computer displaying the physical quantities representing the interactions.