The heightmap library contains functionality for global heightmap/reliefmap manipulation for random maps.

What is a heightmap?

A heightmap or reliefmap is an array of map width +1 arrays of map depth +1 numbers. The values define how high a given vertex between terrain tiles is compared to the default water level (not that of the map!) in meters. By default the heightmap is stored in g_Map.height (see the map object in map.js). The limits are given by the engine and are stored in library.js​ of the more fundamental rmgen library:

• SEA_LEVEL The default water height of 20 meters (above the minimum value) that will count as 0 for the height values in the heightmap
• MAX_HEIGHT_RANGE The difference of minimum and maximum height values the engine allows, roughly 712 (values out of range will be cut to minimum and maximum value)
• MIN_HEIGHT The minimum value of a heightmap of -20 (not cut by the engine)
• MAX_HEIGHT The maximum value of a heightmap of roughly 692

Between those vertices the terrain tiles are placed (which is why there is one tile less in x/y direction then vertices). To get a better feeling for what one heightmap unit means for random maps: Terrain tile width = 4 meters.

General heightmap functionality

The file heightmap.js​ contains the fundamental tools to work with heightmaps.