All map generator algorithms have a few common parameters, plus any mapgen-specific options such as noise parameters or threshhold values. Only mapgen-generic parameters are listed here; mapgen-specific ones are listed in the corresponding mapgen wiki page.

Mapgen parameter source precedence

There are several sources which the map generator may retrieve parameters from. In order from highest precedence to lowest they are:

Hard-coded
Lua mods
map_meta.txt
Game-specific config file
Global config file
Default settings (set in defaultsettings.cpp)
Default object constructor values

List of mapgen parameters

Mapgen name

The name of the map generator algorithm being used. Currently supported:

Mapgen name	Developer responsible	Description
v6	kwolekr, celeron55	The current default map generator. Uses an improved Mapgen v2 algorithm for base terrain; terrain is generated entirely using 2D Perlin noise.
v7	kwolekr	The next generation map generator with an emphasis on generating interesting and playable terrain. Has full support for the internal biome infrastructure and uses a mixture of 2D and both positive and negative 3D noise for terrain.
indev	proller	Mapgen v6 with some interesting experimental features and tweaks added, such as floatlands, terrain that gets higher in scale the further the from the origin, and extremely large caves.
math	proller	Generates terrain based off of 3d fractals, e.g. Mandelbulb. Not intended to be used for a traditional game of Minetest.
singlenode	celeron55	Places only a single node everywhere, namely the one aliased to mapgen_singlenode (by default air). Intended to be used by mods that perform total mapgen takeovers.

Seed

A 64-bit unsigned integer value. At this time, only the lower 32 bits are currently used for randomization.

Water level

The y coordinate at which water starts being placed, for mapgens that do place water.
This is also the position at which blocks are assumed to be underground if no block above is present, and thus is not given sunlight.

Flags parameter

The flags parameter is a set of booleans indicating whether or not a certain option is enabled. Flags can be a combination of the possible values detailed in the table below.
Like all other config and Lua flag fields, they are represented as a comma-delimited string. E.g. the flag string "trees, caves, flat" would direct the Mapgen to create flat terrain with trees and caves.
An exhaustive list of currently recognized Mapgen flags:

Lua/config flag name	Internal constant	Respected by	Description
trees	MG_TREES	v6, indev	Place trees on the map according to the tree noise distribution.
caves	MG_CAVES	v6, indev, v7	Carve out caves from the terrain.
dungeons	MG_DUNGEONS	v6, indev, v7	Randomly place dungeons onto the map.
flat	MG_FLAT	v6, indev, v7	Make all terrain occur at the y position 0, resulting in a flat map. Note that this attribute does NOT turn off trees, caves, or any other feature.
nolight	MG_NOLIGHT	v6, indev, v7, singlenode	Do not calculate lighting; instead leave set to 0 (total darkness). This is intended to be set by custom Lua map generators, NOT end users.
v6_jungles	MGV6_JUNGLES	v6, indev	Place 0.3-style jungles on the map according to v6's own (NOTE: not biome) humidity noise distribution.
v6_biome_blend	MGV6_BIOME_BLEND	v6, indev	Dither nodes between biomes to create a transition between them.
v7_mountains	MGV7_MOUNTAINS		Place 3d noise-defined mountains. Currently, not user-accessible.
v7_ridges	MGV7_RIDGES		Place 3d noise-defined rivers and ridges. Currently, not user-accessible.

Chunk size

The side length (in MapBlocks) of the cubic area that is generated at once. Default is 5; larger values take longer to generate but blocks generate quicker on average and could produce larger, more intricate caves and dungeons.
Don't mess around with this if you don't know what you're doing! This parameter cannot be modified through the Lua API.

Mapgen Parameter Lua API

The task of getting and setting mapgen parameters is much trickier than it seems it should be. For this reason there exists a small but effective set of API for accomplishing this.

minetest.register_on_mapgen_init()

Reading the configuration file for parameter overrides is incorrect, since there are many other sources the mapgen parameters could be set according to. Further, since the map metadata is only loaded after the mods have initially run and before the environment has been created, a direct query cannot be made. For this reason there is a callback that can be registered on mod load, using minetest.register_on_mapgen_init(), which runs on mapgen initialization. If certain decorations, or nodes, etc. must be registered according to the mapgen being used or any other mapgen params, this is the appropriate callback in which to perform these tasks.
minetest.register_on_mapgen_init(function(mgparams)) is passed a table containing the mapgen parameters currently being used.
Valid fields of mgparams are: mgname, seed, water_level, flags

minetest.set_mapgen_params()

This is the API used to set mapgen parameters from within Lua. It may ONLY be executed within a minetest.register_on_mapgen_init callback; calls made outside will not have any effect. If there are multiple callbacks registered to run on_mapgen_init and there are multiple calls to set_mapgen_params, the effective parameter modification is the one passed to the most recent call to minetest.set_mapgen_params(). Also, since parameter modification does not take effect until after all on_mapgen_init callbacks have been completed, prior staged changes are not visible to later callbacks.
minetest.set_mapgen_params(params) is passed a table containing the mapgen parameters that are staged to be modified; valid fields are: mgname, seed, water_level, flags, and flagmask. The flags field is a comma-delimited string of flag names as described in the previous section that are to be SET; the flagmask field is a comma-delimited string of flag names that are to be MODIFIED. In other words, to set a flag, it must be present in both flags and flagmask fields, and to unset a flag, it must be present in the flagmask field but not in the flags field. If a flag is present in flags but not in flagmask, the result is undefined.

Mapgen Parameters

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