To better understand why there are two separate sets of points in the scene, note that a point array (CAD object) is used to create a uniformly spaced base set. The array object always preserves its grid topology as you move it around the scene. However, the transmitters or receivers associated with this point array object are elevated above the irregular terrain and no longer follow a strictly uniform grid. If you move the base set from its original position to a new location, the base points' topology will stay intact, while the associated transmitters or receivers will be redistributed above the terrain based on their new elevations.
== Scene Discretization & Adjustment Running A SBR Simulation ==
=== The Need For Discretization Of Propagation Discretizing the Scene ===
In a typical SBR simulation, a ray is traced from the location of the source until it hits a scatterer. The [[SBR Method|SBR method]] assumes that the ray hits either a flat facet of the scatterer or one of its edges. In the case of hitting a flat facet, the specular point is used to launch new reflected and transmitted rays. The surface of the facet is treated as an infinite dielectric medium interface, at which the reflection and transmission coefficients are calculated. In the case of hitting an edge, new diffracted rays are generated in the scene. However, only those who reach a nearby receiver in their line of sight are ever taken into account. In other words, diffractions are treated locally.
You can build a variety of surface and [[Solid Objects|solid objects]] using [[EM.Cube]]'s native "Curve" CAD objects like lines, polylines, circles, etc. You can use tools like Extrude, Loft, Strip-Sweep, Pipe-Sweep, etc. to transform curves into surface or [[Solid Objects|solid objects]]. '''However, keep in mind that all the "Curve" CAD objects are ignored by the SBR mesh generator and are therefore not sent to the simulation engine.'''
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=== Special Discretized Object Types ===
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In [[EM.Cube]], terrain objects are represented by and saved as special "Tessellated" objects with quadrilateral cells. This is true of terrain objects that you create yourself using [[EM.Cube]]'s Terrain Generator as well as all the terrain objects that you import from external files to your project. The center of each cell represents the terrain elevation at that point. Tessellated objects are considered as discretized objects by [[EM.Cube]] and they are not meshed one more time by the SBR mesh generator. Each quadrilateral cell is divided into two triangular cells before being passed to the SBR simulation engine. Therefore, when using [[EM.Cube]]'s Terrain Generator to create a new terrain object, you have to pay special attention to the resolution of the terrain object as it determines the total number of terrain facets sent to the simulation engine. A high resolution terrain, although looking better and more realistic, may easily lead to an enormous computational problem.
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You can use [[EM.Cube]]'s "Polymesh" tool to discretize solid and surface CAD objects. You can manually control the mesh characteristics of polymesh objects including inserting new nodes on faces and edges or deleting existing nodes. In addition, [[EM.Cube]]'s Solid Generator and Surface Generator tools create ploymesh solids and surfaces, respectively. Like tessellated object, polymesh objects are also considered as discretized objects by [[EM.Cube]] and they are not meshed again by the SBR mesh generator.
=== Viewing SBR Mesh ===
Figure 1: [[Propagation Module]]'s Mesh Settings dialog.
=== Special Discretized Object SBR Simulation Types === In [[EM.Cube]], terrain objects are represented by and saved as special "Tessellated" objects with quadrilateral cells. This is true of terrain objects that you create yourself using [[EM.Cube]]'s Terrain Generator as well as all the terrain objects that you import from external files to your project. The center of each cell represents the terrain elevation at that point. Tessellated objects are considered as discretized objects by [[EM.Cube]] and they are not meshed one more time by the SBR mesh generator. Each quadrilateral cell is divided into two triangular cells before being passed to the SBR simulation engine. Therefore, when using [[EM.Cube]]'s Terrain Generator to create a new terrain object, you have to pay special attention to the resolution of the terrain object as it determines the total number of terrain facets sent to the simulation engine. A high resolution terrain, although looking better and more realistic, may easily lead to an enormous computational problem. You can use [[EM.Cube]]'s "Polymesh" tool to discretize solid and surface CAD objects. You can manually control the mesh characteristics of polymesh objects including inserting new nodes on faces and edges or deleting existing nodes. In addition, [[EM.Cube]]'s Solid Generator and Surface Generator tools create ploymesh solids and surfaces, respectively. Like tessellated object, polymesh objects are also considered as discretized objects by [[EM.Cube]] and they are not meshed again by the SBR mesh generator.  === SBR Mesh Rules & Considerations === Coming Soon... == Running A SBR Simulation ==
[[EM.Cube]]'s [[Propagation Module]] offers three types of ray tracing simulations: