# Direction Modify

- Type
- Line
- Projection
- View

Change here the properties of a crystallographic or atomic direction (or list of directions, previously selected with Direction->Select, when Global is pressed). Parameters for empty entries or Local choices remain unchanged.

To change the direction name write the new name in the Direction entry, followed by the direction number (GAMGI only needs the number to identify the 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.
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