# Map Definition
A region's terrain: four planes of 64 by 64 tiles, each with a height, a ground overlay and
underlay, and its settings flags.


- - -

## MapDefinition.Create
```pascal
function TMapDefinition.Create(regionX, regionY: Integer; const data: TByteArray): TMapDefinition; static;
```
Decodes a region's terrain: four planes of 64 by 64 tiles, each with its height, its ground
overlay and underlay, and its settings flags.

Tiles are written in plane, then x, then y order with no separators - each one is a run of
attribute values that ends at `0`, or at `1` followed by the tile's height. Attributes from `2`
to `49` carry the overlay along with the shape and rotation it is drawn at, `50` to `81` are the
settings flags, and anything above that is the underlay.

A height of `-1` means the tile had none stored and takes the procedural one instead - see
{ref}`TRegion.LoadTerrain`.