=== Impenetrable Surfaces For Outdoor Scenes ===
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[[File:PROP14(2).png|thumb|250px|[[Propagation Module]]'s Impenetrable Surface dialog]]
In outdoor propagation scenes such as "Urban Canyons", you are primarily interested in the wireless coverage in the areas among buildings. You can assume that rays bounce off the exterior walls of these buildings but do not penetrate them. In other words, you ignore the transmitted rays and assume that they are either absorbed or diffused inside the buildings. This is not an unrealistic assumption. EM.Cube offers "Impenetrable Blocks" to model buildings in outdoor propagation scenes. A penetrable block has a color or texture property as well as material properties: permittivity (e<sub>r</sub>) and conductivity (s). By default, a brick building is assumed with ε<sub>r</sub> = 4.4 and σ = 0.001 S/m. Impinging rays are reflected from the facets of impenetrable buildings or diffracted from their edges.
# The electromagnetic model that determines ray-block interaction is selected under '''Specular Interface Type'''. Two options are available: '''Standard Material''' or '''User Defined Model'''. The former is the default choice and requires material properties, '''Permittivity''' (ε<sub>r</sub>) and '''Electric Conductivity''' (σ), which are set to "Brick" by default. No magnetic properties are allowed for blocks.
# Click the '''OK''' button of the dialog to accept the changes and close it.
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[[File:PROP14(2).png]]
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Figure 1: [[Propagation Module]]'s Impenetrable Surface dialog.
Under an impenetrable block group, you can draw any of EM.Cube's native solid or [[Surface Objects|surface objects]] or you can import external model files like STEP, IGES or STL. You can change the properties of an impenetrable surface. In the property dialog of the surface group, click on the table that list the properties to select and highlight a row. Then, click the '''Add/Edit''' button to open up the "Edit Layer" dialog. In this dialog, you can change the name of the material and its permittivity and electric conductivity. The box labeled "Specify Loss Tangent" is unchecked by default. If you check it, you can specify the '''Loss Tangent''' of the material, which, in turn, updates the value of electric conductivity at the center frequency of the project. You can also use EM.Cube's Material List, which will be explained later.
[[File:PROP23.png]]
Figure 2: [[Propagation Module]]'s "Edit Layer" dialog corresponding to impenetrable surfaces.
=== Penetrable Surfaces For Indoor Scenes ===