Changes

[[EM.Terrano]]'s SBR solver uses a method known as Geometrical Optics (GO) in conjunction with the Uniform Theory of Diffraction (UTD) to trace the rays from their originating point at the source to the individual receiver locations. Rays may hit obstructing objects on their way and get reflected, diffracted or transmitted. [[EM.Terrano]]'s SBR solver can only handle diffraction off linear edges and reflection from and transmission through planar interfaces. When an incident ray hits the surface of the obstructing object, a local planar surface assumption is made at the specular point. The assumptions of linear edges and planar facets are valid in in the case of a scene with cubic buildings and a flat global ground.

In many practical scenarios, however, your buildings may have curved surfaces, or the terrain may be irregular. [[EM.Terrano]] allows you to draw any type of surface or solid geometric objects such as cylinders, cones, etc. under impenetrable and penetrable surface groups or penetrable volumes. [[EM.Terrano]]'s mesh generator creates a triangular surface mesh of all the objects in your propagation scene, which is called a facet mesh. Even the walls of cubic buildings are meshed using triangular cells. This enables [[EM.Terrano]] to properly discretize composite buildings made of conjoined cubic objects.

Unlike [[EM.Cube]]'s other computational modules, the density or resolution of [[EM.Terrano]]'s surface mesh does not depend on the operating frequency and is not expressed in terms of the wavelength. The sole purpose of [[EM.Terrano]]'s facet mesh is to discretize curved and irregular scatterers into flat facets and linear edges. Therefore, geometrical fidelity is the only criterion for the quality of a facet mesh. It is important to note that discretizing smooth objects using a triangular surface mesh typically creates a large number of small edges among the facets that are simply mesh artifacts and should not be considered as diffracting edges. For example, each rectangular face of a cubic building is subdivided into four triangles along the two diagonals. The four internal edges lying inside the face are obviously not diffracting edges. A lot of subtleties like these must be taken into account by the SBR solver to run accurate and computationally efficient simulations.

You can view and examine the discretized version of your scene objects as they are sent to the SBR simulation engine. You can adjust the mesh resolution and increase the geometric fidelity of discretization by creating more and finer triangular facets. On the other hand, you may want to reduce the mesh complexity and send to the SBR engine only a few coarse facets to model your buildings. The resolution of [[EM.Terrano]]'s facet mesh generator is controlled by the '''Mesh Cell Size''' parameter, which is expressed in project length units. The default mesh cell size of 100 units might be too large for non-flat objects. You may have to set a smaller mesh cell size in [[EM.Terrano]]'s Mesh Settings dialog, along with a lower curvature angle tolerance value to capture the curvature of your curved structures adequately.