=== Using Terrain Generator ===
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[[File:PROP18.png|thumb|[[Propagation Module]]'s Terrain Generator dialog]]
EM.Cube provides a convenient and powerful Terrain Generator for creating a variety of terrain surface objects. EM.Cube's Terrain Generator looks very similar to CubeCAD's Surface Generator. However, whereas the Surface Generator creates a generic or polymesh surface object, Terrain Generator always creates another special type of object known as a '''Tessellated Object'''. A terrain object is much simpler than EM.Cube's polymesh objects and is usually made up of triangular or quadrilateral facets. As such, terrain objects have limited editing capabilities. For example, you can cut, copy, paste, translate or rotate terrain objects. But operations like scaling, mirroring, grouping (composite), arraying, exploding, linking or Boolean operations do not work on terrain objects.
In all of the above models, you can set the height of the surface object to an any desired value. You set the lateral extents of the surface and its resolution along the X and Y directions in the boxes labeled '''Range Start''', '''Range Stop''' and '''Range Step'''. The step values along the X and Y directions are a measure of surface smoothness: the smaller the step values, the higher the resolution and the smoother the resulting terrain object.
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[[File:PROP18.png]]
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Figure: [[Propagation Module]]'s Terrain Generator dialog.
Some surface types have an additional shape factor called '''Alpha''' that is identical to the alpha parameter in the surface generator. For example, a Gaussian Hump is defined as exp(-r<sup>2</sup>/(2a<sup>2</sup>)), where r is the polar radius. For a Super-quadratic Hump, the input parameter a defines the degree of the super-quadratic surface. a = 2 corresponds to an ellipsoid. Larger values of a get close to a rectangular base with rounded corners. An undulated sinusoidal surface is defined by cos(pax/D<sub>x</sub>)*cos(pay/D<sub>y</sub>), and an undulated sinc is defined by D<sub>x</sub>*D<sub>y</sub>*sin(pax/D<sub>x</sub>)*sin(pay/D<sub>x</sub>)/(2pxy), where D<sub>x</sub> and D<sub>y</sub> are the X and Y dimensions, respectively. Terrain Generator creates a unit cell based on the specified surface type. From the same dialog, you can also produce an array arrangement of such unit cells. Simply enter any number of elements along the X and Y directions in the boxes labeled '''Array'''.