Set here the properties of a crystallographic or atomic direction.
Reference
GAMGI can handle crystallographic directions, related with a cell containing
the relevant crystallographic information, and atomic directions, defined by
two non-coincident atoms.
To create crystallographic directions, set 
Reference to 
Cell.
GAMGI automatically shows a 
Cell entry, plus 
u, 
v, 
w
entries to indicate the direction indices, plus a 
Vectors menu, to select 
the cell vectors to use, 
Conventional or 
Primitive. For the sake of 
simplicity, GAMGI does not accept 4-indice notation for planes or directions 
in hexagonal cells.
Pressing the mouse over a cell in the current layer, the cell identification
is automatically written in the 
Cell entry. When a valid cell is found
and its 
Type is 
Projection, the default 
Line page
is automatically replaced by a 
Projection page.
By default, only one family of crystallographic directions is created.
To create a set of families simultaneously, press the button 
Set (TODO).
When 
Reference is set to 
Atoms, GAMGI automatically shows
two 
Atom entries. Pressing the mouse sucessively over two
non-colinear atoms in the current layer, the two entries become occupied
and the direction defined. After pressing 
Ok, an error is shown 
if the atoms are coincident.