In [[Building Geometrical Constructions in CubeCAD | CubeCAD]], geometric objects are simply grouped together by their color. They do not have any physical properties. However, in all of [[EM.Cube]]'s computational modules, you need to assign physical properties to each geometric object. In these modules, geometric objects are grouped together by their common physical properties as well as their color. The types of physical properties may differ in different computational modules, but they are typically related to the material properties or boundary conditions.
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[[Image:MAT1_new.png|thumb|left|350px|A structure made up of two PEC plates and objects made of different dielectric materials.]]
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From an electromagnetic modeling point of view, materials are categorized by the constitutive relations or boundary conditions that relate electric and magnetic fields. In general, an isotropic material medium is macroscopically characterized by four constitutive parameters: