The electrodes can have either axial or planar symmetry.
When the symmetry is axial (sometimes also called ‘cylindrical’) the coordinates are the radius r and the axial position z. When the symmetry is planar the coordinates are x and z while y goes from plus to minus infinity.
The (r,z) or (x,z) cross-sections through the electrodes to be made up from straight lines and arcs of circles (which can be stretched to form ellipses).
The co-ordinates are (x,y,z) and the electrodes can be made up from rectangles, spheres, cylinders, cones, discs or toroids, or parts of these.
In all cases the electrodes can be stretched, squashed, clipped or cropped.
The electrodes are automatically subdivided into either rectangles (eg for a cylinder) or triangles (eg for a sphere).
The electrodes are treated by the program as the sites of thin sheets of charge. These are the charges that exist physically when a voltage is applied to an electrode. A thick electrode has charges on both sides but a thin electrode can be treated as a single sheet of charge as far as the calculation of potentials is concerned.
In the Boundary Element Method there are no nodal points in the space enclosed by the electrodes. These are not needed. They do not exist in reality.
There are therefore no problems in creating very small structures (eg carbon nano-tubes) in the presence of much larger structures.
In the Boundary Element Method there is no need to have a bounding electrode or to enclose a system.
Users can also use their own equations to define non-standard shapes.