CPO2D is designed to deal with systems that have axial or planar symmetry.
CPO3D will deal with systems of more general symmetry, or no symmetry at all!
In both case use can be made of any of the following planes of reflection symmetry that might exist.
CPO2D, axial symmetry: z =0,
CPO2D, planar symmetry: x =0, z= 0,
CPO3D, x =0; y= 0; z= 0; x= y.
For each of these planes the geometry is symmetric, but the voltages can be symmetric or antisymmetric.
The number of segments is effectively doubled for each reflection plane that is used, giving increased accuracy.