* '''[[Hybrid_Modeling_using_Multiple_Simulation_Engines#Generating_Huygens_Surface_Data | Huygens Surface Data]]'''
=== Visualizing Current Distributions === Current distributions are visualized on the surface of the PO mesh cells, and the magnitude and phase of the electric and magnetic surface currents are plotted for all the objects. In order to view these currents, you must first define a current distribution observable before running the PO simulation. A single current distribution node in the navigation tree holds the current distribution data for all the objects in the project workspace. After a PO simulation is completed, new plots are added under Since the current distribution node. Separate plots are produced for the magnitude and phase of each of the electric and magnetic surface current components (X, Y and Z) as well as the total current magnitude. The current distributions currents are plotted on the surface of the individual mesh cells. As a result, some parts of the plots may be blocked by and hidden inside smooth and curved objects. To be able to view those parts, you may have to freeze the obstructing objects or switch to the mesh view mode. [[Image:Info_icon.png|40px]] Click here to learn more about '''[[Data_Visualization_and_Processing#Visualizing_3D_Current_Distribution_Maps | Visualizing 3D Current Distribution Maps]]'''.
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=== Near-Field Visualization ===
[[Image:PO42(4).png|thumb|350px|EM.Illumina's Field Sensor dialog.]]
EM.Illumina allows you to visualize the near fields at a specific predefined field sensor planeof arbitrary dimensions. Calculation of near fields is a post-processing process and may take a considerable amount of time depending on the resolution that you specify.
{{Note|Keep in mind that since Physical Optics is an asymptotic method, the field sensors must be placed at adequate distances (at least one or few wavelengths) away from the scatterers to produce acceptable results.}}
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=== Computing Radiation Patterns === Physical Optics is an open-boundary technique, and you do not need a far field box to perform near-to-far-field transformations. Nonetheless, you still You need to define a far field observable if you want to plot the radiation patternsof your physical structure. After a PO simulation is finished, three 3D radiation patterns plots are added to the far field node in the Navigation Tree. These are the far field component in θ direction, the far field component in φ direction and the total far field. The 3D plots are displayed in the project workspace and are overlaid on your physical structure.
[[Image:Info_icon.png|40px]] Click here to learn more about the theory of '''[[Computing_the_Far_Fields_%26_Radiation_Characteristics| Far Field Computations]]'''.
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=== Computing Radar Cross Section === When the your physical structure is excited by a plane wave source, the calculated far field data indeed represent the scattered fields. EM.Illumina calculates the radar cross section (RCS) of a target. Three RCS quantities are computed: the θ and φ components of the radar cross section as well as the total radar cross section, which are dented by σ<sub>θ</sub>, σ<sub>φ</sub>, and σ<sub>tot</sub>. In addition, EM.Illumina calculates can calculate two types of RCS for each structure: '''Bi-Static RCS''' and '''Mono-Static RCS'''. In bi-static RCS, the structure is illuminated by a plane wave at incidence angles θ<sub>0</sub> and φ<sub>0</sub>, and the RCS is measured and plotted at all θ and φ angles. In mono-static RCS, the structure is illuminated by a plane wave at incidence angles θ<sub>0</sub> and φ<sub>0</sub>, and the RCS is measured and plotted at the echo angles 180°-θ<sub>0</sub>; and φ<sub>0</sub>. It is clear that in the case of mono-static RCS, the PO simulation engine runs an internal angular sweep, whereby the values of the plane wave incidence angles θ and φ are varied over the entire intervals [0°, 180°] and [0°, 360°], respectively, and the backscatter RCS is recorded.
To calculate RCS, first you have to define an RCS observable instead of a radiation pattern. At the end of a PO simulation, the thee RCS plots σ<sub>θ</sub>, σ<sub>φ</sub>, and σ<sub>tot</sub> are added under the far field section of the navigation tree. Keep in mind that computing the 3D mono-static RCS may take an enormous amount of computation time.
