Set here default visual data that does not depend of the atomic element.
Style
The 
Style menu is to select the default atom visual representation.
Currently supported styles are: 1) a sphere, for 
Solid; 2) a cross, for
Wired. The sphere gives a hight visual quality, when coupled with lights
and perhaps a perspective projection. A sphere uses considerable screen space
though and is time consuming.
The cross uses much less screen space and computing time. Moreover, when atoms
are bonded, crosses are not represented at all, and atoms are identified just
by the ends of the bond lines, decreasing even further computation needs.
However, wired objects do not have a 3D representation, so diffuse and
specular lights are not reflected, becoming poorly visible when using
lights, unless the ambient component is important, about (0.5, 0.5, 0.5).
Size
The 
Size menu is to select the default atom size.
The intrinsic size of an atom is given by:
Size x (Variancy x Radius + (1 - Variancy) x Min)
where 
Radius is the atom radius and 
Min is the minimum
radius.
In 
Wired mode, all atom crosses have a constant size, given by 
Size x 
Min, as 
Variancy is 
0.0.
In 
Solid mode, 
Size selects the default size of the atom spheres.
Combining default atom 
Size and 
Variancy with default bond 
Size,
it is possible to obtain a wide range of styles to represent atomic structures.
In 
Solid mode, the default is to represent atoms as constant
spheres (
Variancy = 
0.0 and 
Size = 
0.8),
slightly larger than the bonds (
Size = 
0.5). An elegant
style is to represent atoms as constant spheres with the same 
Size
as bonds (
0.5).
To represent compact cristalline structures, atom 
Size
and 
Variancy must be 
1.0, to be consistent with
cell dimensions. This style can also be used to represent molecules,
in order to emphasize the atomic radius and electronic distribution.
Variancy
Choose here the default value for 
Variancy.
In 
Wired mode, 
Variancy is always 
0.0.
In 
Solid mode, by default 
Variancy is 
0.0 so the atom 
spheres have all the same size. When 
Variancy is 
1.0 the atom 
spheres are scaled directly by the atom radius.
Min
Min fixes the minimum size for crosses and spheres, as defined by
the equation above for 
Size. By default this is the H covalent radius.
Slices
In 
Solid mode, sets the number of fragments used to represent 
curved surfaces such as atom spheres and bond cylinders, thus controlling 
the visual quality of these objects. Increasing the number of fragments
improves noticeably the visual quality but also decreases performance 
substantially.
Width
In 
Wired mode, controls the line width used to draw atoms and bonds.