# Overlay Definition
Ground overlays: the paths, water and floors drawn on top of the terrain's base colour.


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## OverlayDefinition.Create
```pascal
function TOverlayDefinition.Create(id: Integer; const data: TByteArray): TOverlayDefinition; static;
```
Decodes a ground overlay - the paths, water and floors drawn on top of the underlying terrain
colour.

An overlay is drawn from whichever it has: a secondary colour, a texture, or its own colour.
Both colours are converted to HSL here so the map renderer can pack them into a palette index
without redoing the conversion per tile.


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## TOverlayDefinitionArray.IndexOf
```pascal
function TOverlayDefinitionArray.IndexOf(id: Integer): Integer;
```
The position of `id` in the array, or `-1` if there is no such overlay.

Overlay definitions are stored one per id with no gaps, so an id is its own index; this exists to
keep that assumption in one place.