Random map generation

Features & systems·Scenarios & AI·Maps & scenarios

Changed in 0.2.0

The random map generator builds a map from a map seed. A seed holds twenty settings and no map data: no cells, no tiles and no waypoints. From those settings the generator makes the terrain, water, cliffs, roads, buildings, tiberium and one start point per player. Map seed files covers the file itself, including how it is recognized and why the two size settings are indices, not cell counts. This page covers what the generator does with the settings.

A seed is one [RandomMap] section holding all twenty:

map seed file

[RandomMap]
Description=Four-player temperate map
Width=2            ; size index from 0 to 3, not a cell count
Height=2
NumPlayers=4       ; start points, and the row of map sizes Width and Height pick from
Seed=9021          ; starts the generator's random sequence
Biome=2            ; theater and ground cover; 2 is temperate
Time=1             ; ambient light and floodlights; 1 is afternoon
RegionSize=40      ; how large a piece of ground may stay at one height
Ruggedness=4       ; how far hills rise and fall
Accessibility=50   ; chance that two regions get extra ramps between them
WaterAmount=30     ; how much water the river and lake may lay
Tiberium=10        ; how much tiberium the fields across the map receive
TiberiumLayout=50  ; how many tiberium fields are spread across the map
Vegetation=50      ; chance of green ground and woods
UrbanPresence=2    ; how many settlements are attempted
VeinholeMonsters=4 ; how many veinhole monsters are attempted
TiberiumWildlife=30 ; creature budget of each tiberium field
UseIonStorms=yes   ; loads ION.INI
UseBlueTiberium=no
UseTransitions=no  ; loads the hour's settings file

The passes run in a fixed order, and each reads only a few of the settings. If a setting seems to do nothing, check whether this seed skips the pass that reads it. The passes in order lists the conditions.

The generator makes every random choice from one sequence started from Seed. The same settings with the same game data build the same map, cell for cell. A setting that changes how many random choices an early pass makes also changes every pass after it, so a small change can reshape the whole map.

The dialog path and the scenario path

A seed reaches the generator by one of two routes. Both run the same passes, but only the scenario route builds a map that is played.

Route	Where the settings come from	What is built
The map generator dialog	The dialog’s controls. Loading a saved seed or pressing the randomize button fills the controls first	A preview and its thumbnail. The dialog clears the previous map before each build
A scenario whose filename ends .SED, or whose [Basic] section sets RandomMap=yes	The file’s [RandomMap] section. A setting the section leaves out takes its default. A RandomMap=yes file uses the match’s seed instead of the section’s Seed	The map that is played, built while the scenario loads. The RandomMap=yes page explains which of the file’s other sections still apply

The preview is never played. Accepting the dialog saves its settings to RandMap.Sed and adds that file to the lobby’s scenario list. When the match starts, the scenario route builds the map again from those settings.

Accepting the dialog builds a preview only when none has been built since the dialog opened. Otherwise it reuses the last preview. If a setting changed after the last preview, the lobby thumbnail still shows the older map, while the match uses the new settings.

Both routes hold every setting to its legal range before a map is built. The dialog does this whenever it reads its controls, fills them in or rolls a random set. The scenario route does it after reading the file. Each setting’s key page gives its range.

Sizing and the blank map

The first pass builds the blank map that the other passes work on.

NumPlayers selects a row of minimum and maximum sizes, and Width and Height each pick a point within that row. Map seed files has the table. The result is the playable area. The playfield is four cells wider and twelve cells taller, with the playable area inset two columns and five rows. No setting changes that border.

Biome selects the theater: snow for tundra and taiga, temperate for the other three. Time selects the ambient light level. Every cell starts as Clear ground at height 4, whatever the biome.

Two settings load extra files before any terrain is placed:

• UseTransitions=yes loads the hour’s settings file: MORNING.INI, DAY.INI, DUSK.INI or NIGHT.INI. The map takes its trigger types, tag types and local variables. Its local variables replace any that the scenario file named.
• UseIonStorms=yes loads ION.INI and applies its [General] section over the loaded rules. The map takes IonAmbient, IonRed, IonGreen, IonBlue, IonGround and IonLevel from its [Lighting] section, along with its trigger types and tag types. Ion storms covers what those triggers do.

This pass also decides, with one chance in four, whether a river on this map may have a waterfall.

An ion storm leaves a snow map brighter than it started

A tundra or taiga map is lit at three quarters of the hour’s ambient level. The level an ion storm restores when it ends is the hour’s full level. On a snow map with UseIonStorms=yes, the first storm to end therefore leaves the map brighter than it began.

The passes in order

The passes run in the order below. Each reads only the settings listed beside it. No pass reads Description.

Pass	Settings it reads
Sizing and the blank map	NumPlayers, Width, Height, Biome, Time, UseTransitions, UseIonStorms
Water	WaterAmount, Biome
Ice smoothing	Biome
Regions, cliffs and ramps	RegionSize, Accessibility, Biome
Start points and the layout spread	NumPlayers, TiberiumLayout
Floodlights	Time, UseTransitions, NumPlayers
Veinholes	VeinholeMonsters, Biome
Tiberium	Tiberium, NumPlayers, UseBlueTiberium, TiberiumWildlife
Settlements	UrbanPresence, Biome
Hills	Ruggedness
Ground cover	Vegetation, Biome, Width, Height

Many passes and branches run only under a condition, and most of those conditions are the biome:

Pass or branch	Runs only when
The water pass	WaterAmount is not 0
The river	WaterAmount is above 20, and the biome is not desert
The arctic lake and river, which lay ice	The biome is tundra; taiga uses the ordinary ones
Ice smoothing	The biome is tundra
Region splitting, the source of a generated map’s cliffs	The biome is not tundra
Floodlights	Time is dusk or night, or UseTransitions=yes
Veinholes	The theater is not arctic, so never on tundra or taiga
Creatures in a tiberium field	The Firestorm addon is present, and the field is not a start-point field
Urban areas	The biome is temperate, desert or mutated
Rural settlements	The biome is tundra or taiga
Mold and crystal growths	The biome is mutated
Scattered rock overlays	The biome is temperate, desert or mutated
The hill height walk	Ruggedness is at least 2

Water

WaterAmount sets a budget of water cells, not a share of the map. The budget is WaterAmount times the playable area times a factor for the biome, plus 100 cells. The river and the lake each spend from that budget.

The pass tries to lay one river and then one lake, making up to ten attempts at each. On tundra both are arctic variants that lay ice instead of open water, and the ice smoothing pass then blends the ice into the ground around it. Taiga is also a snow map, but it gets the ordinary river and lake and no ice.

Open water uses tiles from the theater’s WaterSet. On the mutated biome, up to two stretches of the lake are turned into swamp. An ordinary river can include one waterfall, but only on a map where the one-in-four roll allowed waterfalls. A tundra river never has one.

Regions, cliffs and ramps

A region is a group of connected cells at one ground height. Regions decide where a generated map has cliffs, ramps and bridges. The pass builds them in three steps:

1. Each body of water becomes a region and grows four cells outward into the ground around it.
2. The remaining ground is divided into land regions.
3. Any dry region larger than the limit RegionSize sets is split in two, and one half moves to a new height. Splitting repeats until no dry region is over the limit. A higher RegionSize allows larger regions, so the map has fewer height changes.

Nothing places a cliff directly. Cliffs form where the regions from step 3 meet at different heights. Tundra skips step 3, so RegionSize has no effect there.

The pass then connects neighboring regions:

• A water region gets bridges between the dry regions on its banks, but only where both banks stand at the water’s height.
• Where two dry regions meet at different heights, the generator tries to carve one ramp between them. With a chance of about Accessibility percent, rolled once per pair, it tries for one or two more. A pair can get fewer ramps than requested when no suitable spot is found.

Ramp and cliff artwork comes from the theater. Tiles from the cliff roles, including CliffRamps, count as rock face, and the generator does not build over them.

Start points and the layout spread

The start points are chosen from the finished terrain, in the same step as the tiberium field sites:

1. The generator gathers fifteen candidate cells per player. It takes them from the large regions that can reach one another over ground, or from anywhere on the map when no region qualifies. Each candidate must be at least four cells inside the playable area, with a ten-by-ten block around it where a paved road could be laid.
2. From the candidates it picks a spread of cells as far apart as possible. Cells in different regions count as farther apart than they are, so the picks favor separate pieces of ground.
3. The first NumPlayers cells of the spread become the start points. The rest become the tiberium field sites. TiberiumLayout sets how long the spread is, and so how many field sites remain.

Each start point then claims the 400 nearest clear cells as protected ground. Protected ground gets no tiberium, no veinhole and no tree, and no ground-cover patch starts on it. The settlement passes avoid it, and hills do not raise or lower it.

Protected ground can still receive some ground cover. A patch that starts nearby can spread onto it, and scattered rough-ground tiles and rock overlays can land on it.

If any start point cannot reach 400 clear cells, the generator discards all the start points and picks again from the next values in the random sequence. The terrain stays as it is. Nothing limits the number of retries.

Floodlights, veinholes and tiberium

Three placement passes follow, in this order.

Floodlights

The floodlight pass rings each start point with GALITE structures, eight cells out. Time sets how many: none in the morning or afternoon, two at dusk and four at night. UseTransitions=yes always gives four and attaches the hour file’s Light On/Off tag to each. A ring is placed only where every light in it can stand. The generator tries 21 ring angles before it leaves a start point unlit.

Veinholes

The veinhole pass tries to place VeinholeMonsters monsters. It makes at most 200 attempts in total, so a crowded map gets fewer. Each attempt picks a random clear cell and accepts it only when all of these hold, tested in this order:

1. The five-by-five block centered on the cell, plus a one-cell margin around it, lies within the playable area.
2. All of:
   • no cell of the block is protected ground;
   • every cell of the block is clear ground at the center’s height, with no overlay.
3. The veinhole placement test accepts the cell.

An accepted cell takes the VEINHOLE overlay, and its eight neighbors take VEINHOLEDUMMY. Veins are placed on the outer ring of the five-by-five block.

Tiberium

The tiberium pass grows a field at every layout site, then one at each start point.

The layout fields share an amount of tiberium set by Tiberium and NumPlayers. It is divided evenly among them, with a small random variation per field, so more fields means smaller ones.

Each player’s start field has a size of 500, plus 15 for every cell the player sits farther from the layout sites, on average, than the closest player does. The player farthest from the map’s tiberium gets the largest start field, and the closest player gets 500. Tiberium does not change start fields.

A start field’s site is the start point, inside the player’s protected ground. Protected ground takes no tiberium, so the field grows from the edge of that ground.

A field grows outward from its site over clear ground in the playable area. It covers bare cells and thickens tiberium already there.

If growth runs out of room before the field reaches its size, the field starts again from its site. It gets at most nine attempts in all, and a field still short after the last one stays short.

Each field grows one of two tiberium overlay sets:

• With UseBlueTiberium=no, every field grows the first set.
• With UseBlueTiberium=yes, each layout field is rolled separately, with about a 70 percent chance of the first set. All start fields share one roll, with about a 75 percent chance of the first set, so every player starts beside the same kind.

A start field that grows the first set also gets a tiberium tree at its first cell. A layout field that grows the first set has about a one-in-four chance of one.

At the dialog’s setting, a field gets no creatures or a steady stream

The map generator dialog’s check box writes TiberiumWildlife=30. At that figure, each layout field’s creature budget comes out as zero in three draws out of five. In the other two it is effectively unlimited, because of an arithmetic error that TiberiumWildlife explains. A field with the unlimited budget keeps releasing creatures for as long as it grows. On a map built at the dialog’s setting, about two layout fields in five have creatures and the rest have none.

Settlements

UrbanPresence places a different kind of settlement on each group of biomes:

• Tundra and taiga get rural settlements. Each is a dirt road junction on open, unprotected ground, with a few civilian buildings along its roads and a few civilian vehicles.
• Temperate, desert and mutated get urban areas. Each is a paved district grown outward from a cell, with roads, buildings, traffic and a pavement edge.

Either pass stops after ten attempts, however many settlements were asked for. The UrbanPresence page explains what that ceiling does to the setting’s useful range.

Road pieces come from the theater. Rural roads use pieces counted from DirtRoadCurve, and each network starts on a junction from DirtRoadJunction. Urban roads use pieces counted from PavedRoads, and each run ends with a piece from PavedRoadEnds. Neither pass ever selects a ramp piece, so DirtRoadSlopes and PavedRoadSlopes have no effect, and a generated road stops at a slope.

Temperate, desert and mutated maps get no rural settlements

The urban pass contains a branch that would place a rural settlement, with a chance of one minus UrbanPresence. The setting is a whole number from 0 to 100, so that chance is zero or less at every value from 1 up, and at 0 the pass places nothing. These three biomes therefore only ever receive urban areas.

Hills and ground cover

Hills

Hills are raised after the tiberium, settlements and roads are in place. Those features keep their height, and the ground around them rises and falls. A cell keeps its height if any of these holds:

• it holds an overlay, such as tiberium or veins;
• something stands on it, such as a building, a tree or a creature;
• it is protected ground;
• its tile comes from a set without Morphable=yes.

Before the hills are worked out, one clear cell beside each shore tile and each cliff tile is also protected.

Each remaining cell then gets a height offset drawn from the offsets of its neighbors, which makes the ground roll instead of jump. Offsets range from two levels down to two levels up. Ruggedness sets both the size of each step and how far the offsets may wander. The terrain is then raised or lowered one level at a time to meet the offsets, with slopes cut in as it changes. Below Ruggedness=2 this walk is skipped, and the terrain keeps the heights the region pass gave it.

Ground cover

Ground cover is placed last, and the two biome groups are handled differently. Both grow patches of tiles and woods, each from a single cell.

A patch or wood starts only on a cell that is clear ground, has no ramp and is not protected. On temperate, desert and mutated maps, that cell must also have no overlay and nothing standing on it.

From that cell, a patch spreads over neighboring clear ground with no ramp, no overlay and nothing standing on it. Protected ground does not stop it. A wood also spreads, but never onto protected ground.

On temperate, desert and mutated maps:

1. A mutated map first gets mold and crystal growths. Their numbers are drawn from ranges that grow with Width and Height.
2. A desert or mutated map gets 5 to 30 rough-ground tiles scattered across it.
3. Each cell where a patch may start is rolled for green ground, rough ground, sand and woods, in that order. The first roll that succeeds decides what the cell gets, and the rest are skipped. Vegetation scales only the green ground and woods chances. Temperate and mutated maps have no sand chance, and desert maps have no green ground chance.
4. Transition tiles are fixed up, and rock overlays are scattered across the map. A temperate map gets half as many rocks.

On tundra and taiga maps:

1. 5 to 30 rough-ground tiles are scattered across the map.
2. Each cell where a patch may start is rolled separately for a rough patch, a wood and a patch of rock tiles, so one cell can start more than one. Vegetation scales only the woods chance, and there is no green ground.
3. Transition tiles are fixed up. These maps get no rock overlays.

What the theater must supply

The generator takes all its terrain artwork from the tile set roles a theater control file declares. The table groups those roles by the pass that needs them, so a modder adding or renumbering tile sets can see which part of generation a missing role would affect. Theater control files explains how a [General] role is resolved to a tile index.

Pass	Roles it reads
Water and ice	WaterSet, the shore, waterfall and swamp sets, Ice1Set, Ice2Set, Ice3Set, IceShoreSet
Regions, cliffs and ramps	The cliff, slope and ramp sets, CliffRamps among them
Settlements	PavedRoads, PavedRoadEnds, DirtRoadCurve, DirtRoadJunction, and the pavement and median sets
Ground cover	The green, rough, sand, rock, mold and crystal sets

When a map is read, the engine discards the artwork of every tile type that no cell uses yet. A generated map places most of its tiles after that, so a tile set the generator needs must set RequiredForRMG=yes to keep its artwork. The exemption applies only to a generated map: every map the dialog builds, and a scenario whose filename ends .SED or that sets RandomMap=yes.

Handing the map over

When the last pass finishes, the generator starts vein growth and tiberium growth and spread, computes the radar image and returns the finished map to the scenario load.

The multiplayer setup runs only after that, because the start points do not exist until generation ends. Each house’s starting units are created at the generated start points, crates are scattered if the match enables them, and computer players receive their credit multipliers. From then on, a generated map behaves as an ordinary scenario.

Before any of this, the multiplayer and skirmish lobbies check that the chosen scenario has a start point for every player by counting its [Waypoints] entries. A seed file has none, because its start points do not exist until the map is generated. For a file with no waypoints, the lobbies read NumPlayers from its [RandomMap] section instead.

Related settings

Filter keys

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Key	Description	Value	When omitted
Accessibilityrandom map generation	The chance that neighboring pieces of high and low ground are joined by more than one ramp, as a figure from 0 to 100.	integer	0
Biomerandom map generation	The kind of country a generated map is laid out in, as a position from 0 through 4.	integer	0
CliffRampstile controls	Tile set that starts the twenty tiles the random map generator counts as cliff alongside CliffSet.	integer	-1
DescriptionCampaign, map packets, multiplayer maps, random map generation	The text a campaign, a multiplayer map, or a saved map seed is listed under.	string	Varies by type
DirtRoadCurvetile controls	The tile set the whole run of 101 flat dirt road pieces is counted from.	integer	-1
DirtRoadJunctiontile controls	The tile set that supplies the eleven dirt road junctions.	integer	-1
DirtRoadSlopesNo effecttile controls	The tile set that supplies the eight pieces taking a dirt road up a ramp.	integer	-1
HeightBuildingType, SmudgeType, random map generation	A structure's vertical extent, the number of cell rows a smudge covers, or a generated map's size index.	integer	Varies by type
Ice1Settile controls	First of the three sixty-four-tile ice sets a snow theater provides.	integer	-1
Ice2Settile controls	Second of the three sixty-four-tile ice sets a snow theater provides.	integer	-1
Ice3Settile controls	Third of the three sixty-four-tile ice sets a snow theater provides.	integer	-1
IceShoreSettile controls	Forty-eight-tile set of the land-side pieces laid where ice meets ground.	integer	-1
IonAmbientscenarios, random map generation	The light level the map fades toward while an ion storm runs, where 1 is full daylight.	floating point	Context-dependent
IonBluescenarios, random map generation	The blue palette tint in force while an ion storm is running, where 1 leaves the blue channel unchanged.	floating point	Context-dependent
IonGreenscenarios, random map generation	The green palette tint in force while an ion storm is running, where 1 leaves the green channel unchanged.	floating point	Context-dependent
IonGroundscenarios, random map generation	The flat darkening subtracted from every cell while an ion storm is running, as a fraction of full light.	floating point	Context-dependent
IonLevelscenarios, random map generation	The brightness added per height level while an ion storm is running, as a fraction of full light.	floating point	Context-dependent
IonRedscenarios, random map generation	The red palette tint in force while an ion storm is running, where 1 leaves the red channel unchanged.	floating point	Context-dependent
NumPlayersrandom map generation	The number of players a generated map is built for, and the start positions counted for a map without waypoints.	integer	Varies by type
PavedRoadEndstile controls	The tile set that supplies the four caps that close the end of a paved road.	integer	-1
PavedRoadSlopesNo effecttile controls	Tile set of paved road ramp pieces that nothing reads.	integer	-1
PavedRoadstile controls	The tile set the fifteen paved road tiles are counted from.	integer	-1
RegionSizerandom map generation	How large a piece of ground a generated map may hold at one height before it is broken up, as a figure from 0 to 100.	integer	0
RequiredForRMGtile controls	Tile set whose artwork is kept in memory on a generated map even while no cell uses it.	boolean	no
Ruggednessrandom map generation	How hilly a generated map's ground is, as a figure from 0 to 100.	integer	0
Seedrandom map generation	The number the map generator's random sequence is started from.	integer	-1
TiberiumOverlayType, WarheadType, random map generation	Marks an overlay as Tiberium, lets a warhead set Tiberium off, or sets how much Tiberium a generated map receives.	boolean	Varies by type
TiberiumLayoutrandom map generation	How many tiberium fields a generated map is given, as a figure from 0 to 100.	integer	0
TiberiumWildliferandom map generation	Scales how many tiberium creatures each tiberium field spread across a generated map releases, as a figure from 0 to 100.	integer	0
Timerandom map generation	The hour a generated map is fought at, as a position from 0 through 3.	integer	1
UrbanPresencerandom map generation	How many settlements a generated map is given, as a figure from 0 to 100.	integer	0
UseBlueTiberiumrandom map generation	Ignored, because the Firestorm addon alone decides whether a generated map's tiberium fields can grow from the second tiberium overlay set.	boolean	Computed
UseIonStormsrandom map generation	Makes the random map generator load `ION.INI`, the file that sets up a generated map's ion storms.	boolean	no
UseTransitionsrandom map generation	Loads the hour file for a generated map's hour, whose triggers can change the map's lighting during play.	boolean	no
Vegetationrandom map generation	How thickly a generated map is planted with green ground and woods, as a figure from 0 to 100.	integer	0
VeinholeMonstersrandom map generation	Veinhole monsters the random map generator plants.	integer	0
WaterAmountrandom map generation	How much of a generated map is put under water, as a figure from 0 to 100.	integer	0
WaterSettile controls	Fourteen-tile set of open water.	integer	-1
WidthSmudgeType, random map generation	A smudge's width in cells, or a generated map's size index.	integer	Varies by type

Related resources

• Map seed filesFormat
• Theater control filesFormat
• Ion stormsFeature or system
• TiberiumFeature or system
• Veins and veinhole monstersFeature or system
• CratesFeature or system

History

1. Changed0.2.0In development

   Build a random map when a map file asks for one

2. Changed0.2.0In development

   Hold a seed file's settings in range when it is played

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