Underlay Definition

Ground underlays: the base terrain colour that overlays are drawn on top of, and the weight its hue carries when neighbouring tiles are blended together.

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UnderlayDefinition.Create

function TUnderlayDefinition.Create(id: Integer; const data: TByteArray): TUnderlayDefinition; static;

Decodes a ground underlay - the base terrain colour an overlay is drawn on top of.

Beyond the HSL of the colour itself this works out a hue multiplier, which is how heavily this underlay’s hue counts when neighbouring tiles are blended together: a washed out colour has little hue worth spreading, so it is weighted down, while a saturated mid-tone is weighted up. Hue is pre-multiplied by it so that blending is a plain weighted sum.

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TUnderlayDefinitionArray.IndexOf

function TUnderlayDefinitionArray.IndexOf(id: Integer): Integer;

The position of id in the array, or -1 if there is no such underlay.

Underlay 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.