=== SBR Simulation Types ===
Once you have set up your propagation scene in EM.Terrano and have defined sources/transmitters and observables/receivers for your scene, you are ready to run a SBR ray tracing simulation. EM.Terrano offers thee simulation modes (click on each type to learn more about it):
* '''[[#Running a Single{| class="wikitable"|-! scope="col"| Simulation Mode! scope="col"| Usage! scope="col"| Number of Engine Runs! scope="col"| Frequency SBR Analysis ! scope="col"| Restrictions|-| style="width:120px;" | Single-Frequency Analysis]]'''* '''[[Parametric_Modeling,_Sweep_%26_Optimization#Running_Frequency_Sweep_Simulations_in_EM.Cube | style="width:270px;" | Simulates the propagation scene "As Is"| style="width:100px;" | Single run| style="width:200px;" | Runs at the center frequency fc| style="width:150px;" | None|-| style="width:120px;" | Frequency Sweep]]''' * '''[[Parametric_Modeling,_Sweep_%26_Optimization#Running_Parametric_Sweep_Simulations_in_EM.Cube | style="width:270px;" | Varies the operating frequency of the ray tracer | style="width:100px;" | Multiple runs | style="width:200px;" | Runs at a specified set of frequency samples| style="width:150px;" | None|-| style="width:120px;" | Parametric Sweep]]'''| style="width:270px;" | Varies the value(s) of one or more project variables| style="width:100px;" | Multiple runs| style="width:200px;" | Runs at the center frequency fc| style="width:150px;" | None|}
You can set the simulation mode from in EM.Terrano's "Simulation Run Dialog"simulation run dialog. A single-frequency analysis is a single-run simulation. The two other simulation modes in the above list are considered multi-run simulations. If you run a simulation without having defined any observables, no data will be generated at the end of the simulation. In multi-run simulation modes, certain [[parameters]] are varied and a collection of simulation data files are generated. At the end of a sweep simulation, you can graph the simulation results in EM.Grid or you can animate the 3D simulation data from the navigation tree.
{{Note| EM.Terrano's frequency sweep simulations are very fast because the geometrical optics (ray tracing) part of the simulation is frequency-independent.}}
=== Changing the SBR Engine Settings ===
There are a number of SBR simulation settings that can be accessed and changed from the SBR Settings Dialog. To open this dialog, click the button labeled {{key|Settings}} on the right side of the '''Select Engine''' dropdown drop-down list in the Run Dialog. EM.Terrano's SBR simulation engine allows you to separate the physical effects that are calculated during a ray tracing process. You can selectively enable or disable '''Reflection/Transmission''', '''Edge Diffraction''' and '''Terrain Diffraction''' in the "Ray-Block Interactions" section of this dialog. By default, the reflection, transmission and edge diffraction effects are enabled and the terrain diffraction effects are disabled. Separating these effects sometimes help you better analyze your propagation scene and understand the impact of various blocks in the scene.
EM.Terrano allows a finite number of ray bounces for each original ray emanating from a transmitter. This is very important in situations that may involve resonance effects where rays get trapped among multiple surfaces and may bounce back and forth indefinitely. This is set using the box labeled "'''Max No. Ray Bounces'''", which has a default value of 10. Note that the maximum number of ray bounces directly affects the computation time as well as the size of output simulation data files. This can become critical for indoor propagation scenes, where most of the rays undergo a large number of reflections. Two other [[parameters]] control the diffraction computations: '''Max Wedge Angle''' in degrees and '''Min Edge Length''' in project units. The maximum wedge angle is the angle between two conjoined facets that is considered to make them almost flat or coplanar with no diffraction effect. The default value of the maximum wedge angle is 170°. The minimum edge length is size of the common edge between two conjoined facets that is considered as a mesh artifact and not a real diffracting edge. The default value of the minimum edge length is 5 project units.