Figure 3. The geometry of a helix curve and its adaptive FDTD mesh.
===FDTD Mesh Settings=== [[Image:FDTD80.png|thumb|400px|[[FDTD Module]]'s Mesh Settings dialog]]
EM.Cube's [[FDTD Module|FDTD module]] discretizes objects using what is often referred to as the “staircase approximation”. In this mesh generation scheme, the structure is recreated using a large number of cubic cells carefully assembled in a way that approximates the shape of the original structure. By default, a carefully calculated, "<u>'''Adaptive'''</u>" mesh of your physical structure is generated in order to satisfy the following criteria:
Occasionally, you may prefer a more regular FDTD mesh with almost equal grid line spacing everywhere, but still with a frequency-dependent cell size. In that case, you can select the "<u>'''Regular'''</u>" option of the '''Mesh Type '''dropdown list in the FDTD Mesh Settings dialog. The regular FDTD mesh enforces only two of the above parameters: '''Minimum Mesh Density''' and '''Absolute Minimum Grid Spacing'''. Or you may opt for an absolutely "<u>'''Uniform'''</u>" mesh type, for which you need to specify the '''Cell Size '''along the X, Y, Z directions in project units.
[[Image:FDTD80.png]]
Figure 1: [[FDTD Module]]'s Mesh Settings dialog.
===Global vs. Local Control Of FDTD Mesh===