Changes

EM.Terrano's SBR ray tracer solver uses a method known as Geometrical Optics (GO) in conjunction with the Uniform Theory of Diffraction (UTD) to traces trace the rays from their originating point at the source to the individual receiver locations. Ray 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 material interfaces. The underlying theory for calculation of reflection, transmission and diffraction coefficients indeed assumes material media of infinite extents. When a an incident ray hits a specular point on 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.

[[Image:Info_iconIn many practical scenarios, however, your buildings may have curved surfaces, or the terrain may be irregular. EM.png|40px]] Click here Terrano allows you to learn more about the theory 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'''[[SBR Method]]'''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.

If your propagation scene contains only cubic buildings on the flat global groundUnlike [[EM.Cube]]'s other computational modules, the assumptions density or resolution of linear edges and planar facets hold well although they violate the infinite extents assumptionEM. In many practical scenarios, however, your buildings may have curved Terrano's surface or mesh does not depend on the terrain may be irregularoperating frequency and is not expressed in terms of the wavelength. The sole purpose of EM.Terrano allows you 's facet mesh is to draw any type of surface or solid CAD objects under impenetrable and penetrable surface groups or penetrable volumes. Some of these objects contain discretize curved surfaces or curved boundaries and irregular scatterers into flat facets and linear edges such as cylinders, cones, etc. In order to address all such cases in the most general contextTherefore, EMgeometrical fidelity is the only criterion for the quality of a facet mesh.Terrano always uses It is important to note that discretizing smooth objects using a triangular surface mesh typically creates a large number of all small edges among the objects in your propagation scenefacets that are simply mesh artifacts and should not be considered as diffracting edges. Even For example, each rectangular facets face of a cubic buildings building is subdivided into four triangles along the two diagonals. The four internal edges lying inside the face are meshed using triangular cellsobviously not diffracting edges. This is done to A lot of subtleties like these must be able taken into account by the SBR solver to properly discretize composite buildings made of conjoined cubic objectsrun accurate and computationally efficient simulations.

[[Image:prop_manual-29You can view and examine the discretized version of your scene objects as they are sent to the SBR simulation engine.png|thumb|350px|EMYou can adjust the mesh resolution and increase the geometric fidelity of discretization by creating more and finer triangular facets.Terrano's Mesh Settings dialog.]] Unlike [[EM.Cube]]'s On the other computational moduleshand, you may want to reduce the density or mesh complexity and send to the SBR engine only a few coarse facets to model your buildings. The resolution of EM.Terrano's surface facet mesh does not depend on generator is controlled by the operating frequency and '''Mesh Cell Size''' parameter, which is not expressed in terms of the wavelengthproject length units. Its sole purpose is to discretize curved and irregular scatterers into The default mesh cell size of 100 units might be too large for non-flat facets and linear edgesobjects. Therefore, geometrical fidelity is the only criterion for the quality of an SBR mesh. It is important You may have to note that discretizing smooth objects using set a triangular surface smaller mesh typically creates a large number of small edges among the facets that are simply mesh artifacts and should not be considered as diffracting edgescell size in EM. For exampleTerrano's Mesh Settings dialog, each rectangular face of a cubic building is subdivided into four triangles along with a lower curvature angle tolerance value to capture the two diagonalscurvature of your curved structures adequately. The four internal edges lying inside the face are obviously not diffracting edges <table><tr><td> [[Image:prop_manual-29. A lot of subtleties like these must be taken into account by the SBR solver to run accurate and computationally efficient simulationspng|thumb|left|480px|EM. Terrano's mesh settings dialog.]] </td></tr></table>

<td> [[Image:PROP15BPROP MAN9.png|thumb|550pxleft|The brick buildings in an urban propagation scene.]] </td></tr><tr><td> [[Image:PROP15C.png|thumb|550px640px|The triangular surface facet mesh of the building buildings in the urban propagation scenegenerated by EM.Terrano's Random City wizard.]] </td>