### order

A crystallographic plane does not exist as a single plane, is always
part of a family of infinite planes, passing through all the lattice
nodes, with equal distances between them. Each plane of a family
(h k l) intersects the lattice in n/h n/k n/l, where n = 0 means
the plane passing through the origin and n = 1 is the usual
representation of the plane closest to the origin. The

**order**
parameter indicates the value of n for a specific plane.

### o1, o2, o3

A plane can also be defined indicating explicitly the coordinates of
a node where the plane passes. For each plane family, there is a plane
passing through the origin node and as nodes are equivalent, it follows
that for any node, there is a plane of any family passing through there.

When the lattice is primitive or vectors are primitive, coordinates
**o1**, **o2**, **o3** are enough to identify any cell node.
No default node exists as the default plane **order** (**1**)
cannot be associated to a specific node for all lattices.

Example: **<cell ... o1="1" o2="0" o3="0"/>** (no default)
Allowed values: integer (optional, coupled)

### o4

When the lattice is centered and vectors are conventional, the coordinates

**o1**,

**o2**,

**o3** indicate the node in the lower-left
corner of the cell where the plane passes. a fourth coordinate

**o4**
is needed to point the centered node where the plane passes. By default,

**o4** is

**000**, so no change is introduced. When the cell lattice
is primitive

**P** or the vectors defining the node are primitive, that
is the only possible value for

**o4**. For I, C, F, R centered lattices,

**o4** can also take the values:

**I**: **111**
**C**: **110**
**F**: **110**, **101**, **011**
**R**: **211**, **122**
Example: **<plane ... o4="000"/>** (default)
Allowed values: **000**, **111**, **110** **101**, **011**, **211**, **122** (optional)

### data

The geometric data defining a polygon plane must be entered in order to
make the plane completely independent from its reference objects. This is
accomplished with two

**data** child elements, one containig real data
(the xyz coordinates), the other containing integer data (the number of
loops, 1, the number of vertices for the loop, n, the offset of the
vertices for the loop, from 0 to n-1).

Example:
**<data ... name="points" type="double" size="9">
-1.0000 0.0000 0.0000 1.0000 0.0000 0.0000 0.0000 1.0000 0.0000
</data>** Allowed values: real (required)
Example:
**<data ... name="points_driver" type="int" size="5">
1 3 0 1 2 </data>** Allowed values: integer (required)