== Drawing a Metal Sphere ==
When you start drawing in [[EM.Libera]] for the first time in a blank project, a default PEC group called "PEC_1" is created in the navigation tree to hold your CAD objects. In other words, all the objects you draw are assumed to be perfect electric conductors by default. Select Click on the <b>Sphere Tool</b> from [[Image:sphereiconc.png]] button of the Object Toolbar or select the menu item '''Object → Solid → Sphere'''.
<table>
</table>
With the sphere tool selected, click at the origin (0,0,0) of the project workspace to start your drawing, and drag the mouse to draw a sphere. Set the '''Radius''' of the sphere to R = 150mm. When you drew a very large object, it may fill up the entire screen. You can zoom to fit your structure into the screen using the keyboard shortcut <b>Ctrl+E</b> or by clicking the Zoom Extents [[Image:fdtd_zoomextents.png]] button of View Toolbar.
Note that at the center frequency f<sub>o</sub> = 1GHz, the operating wavelength is λ<sub>0</sub> = 300mm, and your sphere has a diameter of one wavelength.
</table>
Next, activated your PEC_1 group from its contextual menu and draw a PEC rectangle strip object. To draw a rectangle, click the '''Rectangle Strip''' [[Image:RectangleStripIconx.png]] button of the Object Toolbar or select the menu item <b>Object → Surface → Rectangle Strip</b>.
<table>