Creation lifecycle and knowledge

Section titled “Creation lifecycle and knowledge”

This page follows physical system creation from game setup or first jump point exploration through stellar components, planets, satellites, small bodies, environments and initial resources. It separates catalogue definitions, shared physical objects and race knowledge. Ongoing movement, terraforming, archaeology and disasters have their own pages.

Dice follow one notation. d10 means a fresh roll of a ten-sided die, 1 to 10 inclusive, and the same holds for any other number of sides. 3 x d10 multiplies one roll. 4d10 sums four independent rolls. Repeated dice are independent. Conversion to a whole number drops the fraction, toward zero. Default rounding sends an exact half to the even neighbour. The formulas keep the game’s own order of operations and comparisons rather than idealised physics.

A new system takes the next system ID and records the system its generation started from, whether it is Sol, and its system number. It then obtains its stellar component descriptions. Stars are created in component order, and each star creates its own bodies before the next star. Generation then prunes distant companions when the Limited Planet Distance option of the Game Information window (FCT_Game.LimitPlanetaryDistance) is on, tries race creation on planets and moons, renumbers asteroids outside Sol, creates jump points and survey locations, applies eligible special features, forces an orbital position update with a step of 10000.0 seconds and finally adds the system to the game.

The race attempt needs a positive system race chance and race creation not skipped. The chance is NPR Generation Chance (by Player) (RaceChance in FCT_Game) for systems found by a player race, NPR Generation Chance (by NPR) (RaceChanceNPR) for systems found by an NPR, and 0 for Sol. Asteroids outside Sol are renamed “Asteroid #1” onward, ordered by star component and then orbital distance.

Stars and bodies are added to the game earlier, as each is made. The steps are applied one after another and are not undone as a group. If an error occurs in the system generation step itself, the game shows error Function #1562 and the generation of that system ends without a system. Stars and bodies already added stay in place. An error inside star creation (Function #1564) or inside the planetary system of one star (Function #1569) ends only that step, and generation of the system carries on. Jump point counts and placement are in jump point creation. The ordinary race attempt is in NPR creation triggers, .

The Create Habitable button of the System Generation and Display window asks for a habitable system. It then creates and removes unsuitable systems repeatedly until one passes the test in setup overrides. The same request also turns on the 70% hydrosphere cap, so asking for a habitable system changes generation before the system is accepted or rejected. After success the game sets up that race’s jump point surveys for the system and creates the race’s system knowledge record (FCT_RaceSysSurvey). Without a race the system is still generated physically, but no knowledge record is made.

First jump point exploration reuses a linked destination, connects to an existing system or generates a new one. Connection selection on first exploration describes that choice. Linking endpoints and numbering describes the reciprocal link, in which each point stores its peer point and its WPLink value.

Stars, bodies, atmospheres, deposits and jump connections are shared physical state. A race’s system knowledge record, geological survey membership, body names (FCT_SystemBodyName) and charted and explored jump point flags are race state. Initial deposits do not require a race to have surveyed the body. Exploration and discovery covers survey completion, and movement covers later positions.

Definitions and stellar selection

Section titled “Definitions and stellar selection”
Input Loaded data and role
DIM_StellarType Mass, luminosity, radius, age range (AgeRangeID), spectral class and number, size, cumulative MaxChance, BDMaxChance, ExtraJP, colours and NotPS. A loaded column is not necessarily read by every generation path.
DIM_KnownSystems Up to four stellar components, C2Orbit, C3Orbit and C4Orbit distances, C3OrbitType and C4OrbitType, XYZ, distance and naming. Rows with GameID 0 or the current game are read. Each component is a copy of its stellar definition. A row that names an invalid stellar type can be skipped.
DIM_SystemAge Ten age values (Age1 to Age10) and ten luminosity modifiers (Lum1 to Lum10) per age range, plus TotalLife.
DIM_SystemAbundance Cumulative thresholds (MaxChance) and abundance modifiers.
DIM_SetAtmosphere and DIM_Gases Cumulative composition choices per temperature band (TempBand) and gas properties.
DIM_SolSystemBodies Fixed Sol profiles instead of procedural slot, type and radius rolls.

With Known Star Systems (UseKnownStars in FCT_Game) at 1, a supplied known-system description is used. Without one the game picks a nearby unused known system. The orbital parameters are then recalculated. With the option off, the game builds a procedural description from the system number, even when a known description was supplied. Only a catalogue description becomes the system’s known system, and its KnownSystemID replaces SystemNumber. A known-star system still receives procedural planets. The catalogue is not an observed-exoplanet list. Sol takes the separate fixed-body path. The known-star catalogue covers the catalogue itself.

A random stellar type rolls d10150 when black holes are allowed, which is the case for the primary of a procedural system, and d10000 otherwise, which is the case for companions. The game copies the first definition with a positive MaxChance, taken in ascending MaxChance order, whose cumulative threshold is at least the roll. Probabilities therefore depend on the thresholds in the game database. A random brown dwarf discards one d23 roll, then picks uniformly among entries with BDMaxChance above 0. The value of BDMaxChance is not a weight. Black holes and brown dwarfs covers catalogue black holes.

Age, multiplicity and stellar orbits

Section titled “Age, multiplicity and stellar orbits”

A procedural description starts with one primary and adds each next component on d10 above 6, nested up to four components. Provided the selections succeed, the attempted multiplicity before pruning is 60% single, 24% binary, 9.6% triple and 6.4% quadruple. One in five secondary attempts (d5 = 1) around a primary that is not a black hole instead looks up the definition with the primary’s spectral class and size and a spectral number of max(d10 - 1, primary number), and uses that definition directly. When the lookup finds no definition, the system gets no secondary. Otherwise the secondary is a random draw without black holes, replaced by a brown dwarf when its mass is at least the primary’s. The tertiary and quaternary compare their mass with the component before them.

The primary sets system age and abundance. Age range B0 to B9 gives age 0.1, and a protostar gives 0.05. Subgiants and giants take the TotalLife of the most massive main-sequence definition (SizeID 5) no heavier than themselves, times 1.1 for a subgiant and 1.2 for a giant. Other age ranges roll one d10 that picks both the age and the primary’s luminosity modifier from DIM_SystemAge. Abundance takes the row with the lowest threshold at least d10 + d10 + age rounded to a whole number (an exact half goes to the even neighbour). In the game database as shipped, DIM_SystemAbundance holds Exceptional (12, +2), High (14, +1), Normal (18, 0), Poor (21, -1), Very Poor (24, -2) and Depleted (1000, -3). A companion’s luminosity uses the first age bin, in ascending order, that is at least the system age, capped at index 10. These ages use the generation’s billion-year scale, not game seconds.

System scale is sqrt(primary mass) at a mass of at most 1, and mass^(1/3) above it. The primary’s jump point survey points are scale x 400 with the fraction dropped. Sol fixes mass 1, age 5, abundance 1, dust 0, race chance 0 and StellarTypeID 1000.

The primary’s coordinates, orbit and bearing are zero. A companion finds its parent star through OrbitingComponent, which holds the number of an earlier star component, and uses the C2, C3 or C4 distance. It receives its age luminosity modifier and a random bearing. Periapsis = a x (1 - e), apoapsis = a x (1 + e) and semi-minor axis = a x sqrt(1 - e²). A star created with a positive explicit distance skips procedural planets. Normal generation gives no explicit distance. A black hole (spectral class BH) also skips planets and primary comets. The eccentricity direction is d3600 / 10 with whole-number division before conversion, which gives whole degrees from 0 to 360.

Stellar distance generation uses a collision floor of (parent radius + child radius) / 50. This differs from the minimum safe orbit of (parent radius + child radius) x 2 that decides tertiary placement. Both act on the stored radius values directly, with no unit conversion. Normally the game picks one of five equally likely scales with d5 and multiplies d100 by the scale chosen from 0.005, 0.05, 0.3, 2 and 20. It repeats until the result is strictly above the minimum and strictly below a nonzero maximum. A minimum above 1000 instead returns minimum x (1 + d100 / 100). Contradictory positive bounds, with the minimum above the maximum, use their midpoint, raised to collision floor x 1.2 when the midpoint falls below the floor.

With Eccentric Orbits (StarEccentricity in FCT_Game) off, stellar eccentricity is 0. Otherwise the roll is d10, minus 2 for an orbit below 0.05 AU or minus 1 below 5 AU.

Roll Stellar eccentricity
Below 2 0.01 x d10, 0.01 to 0.10
2 0.1 + 0.01 x d10, 0.11 to 0.20
3 to 4 0.2 + 0.01 x d10, 0.21 to 0.30
5 to 6 0.3 + 0.01 x d10, 0.31 to 0.40
7 to 9 0.4 + 0.02 x d10, 0.42 to 0.60
10 0.6 + 0.03 x d10, 0.63 to 0.90

A trial is kept when its periapsis lies strictly outside the parent’s radius converted to AU (radius x 0.00465047), is at least a nonzero minimum, and its apoapsis is at most a nonzero maximum. Ten failures force a circular orbit.

In a binary, both components get an exclusion radius of C2 periapsis / 3. A procedural tertiary rolls d3 for its orbit type and then always replaces it. It orbits outside the binary when the C2 distance is below 1 AU. Otherwise a coin flip makes it orbit component 1 or component 2, and it moves outside the binary when the minimum safe orbit exceeds C2 distance / 3. An inner tertiary orbits component 1 or 2 within C2 periapsis / 3 and replaces that component’s exclusion radius with C3 periapsis / 3. An outer tertiary orbits component 1 beyond C2 apoapsis x 3 and gets (C3 periapsis - C2 apoapsis) / 3. Fourth-component rules extend this hierarchy. These exclusion radii are the maximum planetary distances around each component. Catalogue systems recompute the hierarchy from their stored distances and orbit types. In the procedural fourth-component safety checks, some failures write orbit type 4 into C3OrbitType while the fourth component’s placement still follows C4OrbitType. A fourth component of orbit type 4 also takes its exclusion radius from its periapsis before its new periapsis is generated. The catalogue recalculation generates the periapsis first.

With Limited Planet Distance (LimitPlanetaryDistance in FCT_Game) at 1 and more than one star, a companion whose parent star was removed is removed too. A companion whose apoapsis exceeds 160 AU is removed when its periapsis is at least 160 AU and the primary has no gas giant or superjovian. When the count of such giants is above 0, the companion stays if it has a Lagrange point and is removed otherwise. A companion whose orbit crosses 160 AU adds its gas giants and superjovians to that count for the companions after it, once it has been moved inside 160 AU. A companion kept because its orbit stays within 160 AU, or because it has a Lagrange point, adds nothing. A companion with a crossing orbit, with its apoapsis above 160 AU and its periapsis below it, rerolls its bearing as (d3600 - 1) / 10 degrees until its current distance is below 160 AU. This controls the initial position, not future orbital extremes.

Planetary slots, types and stability

Section titled “Planetary slots, types and stability”

The planet-count modifier is +5 for a brown dwarf, +1 for K5 to K9, +2 for M0 to M4 or +3 for M5 to M9, minus the system abundance. For r = d10 + modifier, the star gets d10 + 10 slots at r below 2, d10 + 5 below 6, d10 below 8, d5 below 10 and 0 otherwise. A star with no slots stops there, before the construct potential roll. Slots are candidates, not guaranteed planets.

The first distance is 0.05 x stellar mass² x d10 AU, replaced by 0.001 only when it is exactly 0. When it exceeds a positive exclusion radius, no candidates are added. Each next distance is previous x (1.1 + 0.1 x d10) + 0.1, and the sequence stops at the first distance beyond a positive exclusion radius. Filters then remove distances strictly below an inner limit. A white dwarf’s limit is 1, 2, 4, 6 or 10 AU, picked by d10 + bonus below 3, below 6, below 9, below 12 or otherwise. Its bonus is +2 at a mass of at least 0.6 and another +2 above 0.9. A brown dwarf’s limit is 0.002 AU below mass 0.03 and 0.004 AU otherwise. Other stars use 0.025 x square root of L. A distance equal to the limit survives. Each star with slots then has a 2% construct potential, set on d50 = 25.

The inner zone runs through 4 x square root of L AU inclusive, the outer zone through 50 x square root of L inclusive, and the distant zone beyond. The life zone separately includes both 0.75 x square root of L and 1.4 x square root of L. Maximum satellite distance is (orbit - previous candidate) / 3 x 149,600,000 km. Belt half-width is (orbit - previous candidate) / 2. The previous candidate advances for empty slots and belts too.

Zone and d100 Belt Terrestrial Dwarf Gas giant Superjovian Empty
Inner 1 to 10 11 to 67 68 to 78 79 to 86 87 to 90 91 to 100
Outer 1 to 10 11 to 18 19 to 34 35 to 79 80 to 90 91 to 100
Distant 1 to 10 11 to 13 14 to 35 36 to 39 40 to 47 48 to 100

A body type set by another rule bypasses the table. Empty candidates consume an ID without joining the game. Belts add individual asteroids instead of one planet. Automatic natural Lagrange points require a superjovian (Super Jovian in the game) or a gas giant with mass above 200. Giants get a chance of trojans unless the creating rule suppresses them. Normal generation leaves the trojan count random.

With Gas Giant Effects (GasGiantEffects in FCT_Game) on, planets above mass 50 are processed in descending order of mass. The destabilisation interval is from periapsis x 0.67 to apoapsis x 1.33 below mass 200, from periapsis x 0.5 to apoapsis x 1.5 below 500, and from periapsis x 0.4 to apoapsis x 2 otherwise. Lighter planets strictly inside the interval that are not yet marked are marked once.

  • A dwarf planet survives on d10 below 5, with e increased by 0.04 x d10. Otherwise it is removed, and a roll of 8 to 10 on a planet that is not tidally locked queues a capture.
  • A terrestrial planet survives on d10 below 3 with the same eccentricity increase. A roll of 3 to 6 replaces it with an asteroid belt at the same orbit. Otherwise it is removed, and a roll of 9 to 10 on a planet that is not tidally locked queues a capture.
  • A lighter giant survives with increased eccentricity on d10 below 4 and is removed otherwise.

A changed eccentricity is capped at 0.95 and then reduced in steps of 0.01 until the periapsis and apoapsis fit the star’s bounds. Survivors are renumbered by distance. The special giant marker is assigned separately during physical generation and does not decide which giants take part in this pass.

With Limited Planet Distance on, the limit is 80 x system scale AU. A planet or asteroid with apoapsis above the limit is removed when its periapsis is at least the limit. Otherwise its bearing rerolls as (d3600 - 1) / 10 degrees until its current distance is below the limit. Planets are renumbered again. Only surviving planets that are not tidally locked receive moons afterward.

Physical profiles and environment order

Section titled “Physical profiles and environment order”

A planet’s eccentricity is chosen before its physical and environment stages. The same eccentricity rules also serve asteroids and comets. With Eccentric Orbits off, eccentricity and direction are 0, and periapsis and apoapsis equal the orbital distance. Otherwise the direction is d3600 / 10 with whole-number division, and the roll r = d10 + bonus selects:

Body class Roll bands Eccentricity
Planet below 6 / below 8 / below 10 / otherwise 0.005 x d10 / 0.05 + 0.01 x d10 / 0.15 + 0.01 x d10 / 0.25 + 0.04 x d10
Asteroid below 6 / below 8 / below 10 / otherwise 0.01 x d20 / 0.2 + 0.01 x d10 / 0.3 + 0.01 x d10 / 0.4 + 0.01 x d40
Comet 1 / 2 / 3 / 4 to 5 / 6 to 8 / 9 or more 0.5 + 0.01 x d10 / 0.6 + 0.01 x d10 / 0.7 + 0.01 x d10 / 0.8 + 0.01 x d10 / 0.9 + 0.01 x d9 / 0.99 + 0.001 x d9

Bodies other than comets need a periapsis strictly outside stellar radius x 0.00465047 AU and an apoapsis strictly below a nonzero exclusion limit. The primary’s limit is its exclusion radius x 1.5. Comets skip both checks. After ten failed trials the fallback eccentricity is 0.999, or exclusion limit / a - 1 when the exclusion limit is below 2a. A zero limit can therefore give a fallback of -1 after repeated stellar-radius failures. Semi-minor axis and orbital speed follow. This fallback differs from the circular fallback of stellar components.

Radius is in km. The terrestrial size roll is d10 + abundance, with -2 strictly inside 0.5 x square root of L, clamped to 1 to 10. Another d10 supplies the steps. A gas giant’s size roll is a plain d10.

Size roll Terrestrial radius km Gas giant radius km
1 2000 + 100 x d10 15000 + 300 x d10
2 2000 + 100 x d10 18000 + 300 x d10
3 3000 + 100 x d10 21000 + 300 x d10
4 3000 + 100 x d10 24000 + 300 x d10
5 4000 + 100 x d10 27000 + 300 x d10
6 5000 + 100 x d10 30000 + 1000 x d10
7 6000 + 100 x d10 40000 + 1000 x d10
8 7000 + 100 x d10 50000 + 1000 x d10
9 8000 + 200 x d10 60000 + 1000 x d10
10 10000 + 500 x d10 70000 + 1000 x d10

Dwarf planets use 200 x d10. Superjovians use 60000 + 2000 x max(1, d10 - whole-number(age / 2)).

Terrestrial and dwarf density in the inner zone is min(1.5, 0.3 + q x 0.127 / (0.4 + a / square root of L)^0.67), with q = (d10 + d10 - 1 + radius bonus + abundance) / 2.0. The radius bonus is 2 above 8000 km, 1 above 6000 km and 0 otherwise. Other zones use 0.1 + 0.05 x d10. Gas giant density is 0.08 + 0.025 x d10, plus 0.02 in the inner zone. Its computed size and abundance modifier is not applied to that final d10. Density is relative to Earth in these formulas, not in g/cm³.

Mass of solid bodies and giants in Earth masses is (radius / 6380)³ x density. Gravity in Earth g is max(0.0001, mass / (radius / 6380)²). Escape velocity relative to Earth is sqrt(19600 x gravity x radius) / 11200. Superjovian mass uses a fresh d10 with roll r: 1 to 4 give 500 + 50r, 5 to 7 give 1000 + 100r, 8 to 9 give 2000 + 100r, and 10 gives 3000 + 100r. Density is then calculated back from mass. Gas giants receive the special giant marker on d200 = 50, superjovians on d100 = 50.

A planet’s year is sqrt(a³ / stellar mass) x 8760 hours, with 0 replaced by 1. Tidal force is stellar mass x 26640000 / (a x 400)³. A tidal lock requires (0.83 + 0.03 x d10) x force x age / 6.6 > 1. A locked planet has tilt 0, and others get a random tilt. Day length and tectonics follow. Base temperature (BaseTemp) is max(4, 255 / square root of (a / square root of L)) Kelvin, and the magnetic field comes next.

Bodies other than giants then receive, in order, atmosphere, hydrosphere, the optional 70% cap, evaporation, albedo, the hydrosphere phase transition, the runaway greenhouse check, an atmosphere refresh, a possible ruin or construct for terrestrial planets, minerals and terrain. Giants instead get atmosphere 0, hydrosphere 0 of type None, albedo 1, SurfaceTemp equal to BaseTemp and their own mineral rules. A bearing of d360 - 1 degrees and the coordinates finish initialisation. Planetary terrain describes how the terrain step picks a dominant terrain and which systems read it.

Rotation, tilt, tectonics and magnetic field

Section titled “Rotation, tilt, tectonics and magnetic field”

A locked body sets DayValue equal to its year and skips the day dice. Otherwise the braking score b = d10 + whole-number(tidal force x age / 2) selects the following hours before the final multiplier:

Body types b below 7 b below 9 b below 11 Otherwise
Dwarf planet, small moon, moon, large moon 2 x d10 24 x d10 24 x d100 24 x (100 + d1000)
Terrestrial planet, terrestrial moon, small terrestrial moon 10 + 2 x d10 30 + d100 48 x d100 24 x (100 + d2000)
Other types that reach this step, including giants 6 + d5 11 + d5 16 + d10 26 + d10

The final multiplier is 1 + 0.1 x (whole part of (tidal force x age) + adjustment). The adjustment is -2 for a terrestrial planet with mass above 4, +2 for a gas giant with mass below 50 and 0 otherwise. The axial tilt rolls d5 and gives exactly 1, 12, 23, 34 or 45 degrees with equal probability, not a continuous 0 to 45 range. A planet tidal lock suppresses this roll, and a moon suppresses it at tidal force above 7.

Tectonics starts as Dead, and giants keep it without dice. Other bodies roll a classification d10 first and then activity (5 + d10) x square root of mass / age. Moons halve activity, and multiply it by density when the parent’s zone is not inner and density is at most 0.45. Bodies other than moons apply that cold-density factor using their own zone, then apply the day-length modifiers. A day below 18 hours multiplies their activity by 1.25. Otherwise an unlocked body whose day is at most its year multiplies by 0.75 only when the day exceeds 100 hours, and a locked body or one whose day exceeds its year multiplies by 0.5. Moons skip these day-length modifiers. The final score and the first d10 give:

Score Classification roll outcomes
above 5 1 Plastic, 2 Plate Tectonics, 3 to 7 Platelet Tectonics, 8 to 10 Extreme
above 3 through 5 1 Hot Spot, 2 to 3 Plastic, 4 to 8 Plate Tectonics, 9 to 10 Platelet Tectonics
above 2 through 3 1 to 2 Hot Spot, 3 to 6 Plastic, 7 to 10 Plate Tectonics
above 1 through 2 2 to 5 Hot Spot, 1 and 6 to 9 Plastic, 10 Platelet Tectonics
0.5 through 1 8 to 9 Hot Spot, all others Plastic
below 0.5 Dead

This generated state later affects atmosphere composition and the runaway greenhouse pressure multiplier.

The magnetic field consumes a strength d10 and a magnitude d10 first. For terrestrial and dwarf planets and any moon, the dynamo score is 10 x square root of (24 / DayValue) x density² x square root of mass / age, halved in a zone other than inner when density is below 0.45. The strength bands 1 to 3, 4 to 5, 6 to 7, 8 to 9 and 10 multiply the magnitude die as follows:

Dynamo score Multipliers by strength band
above 4 0.1 / 0.2 / 0.3 / 0.5 / 1
above 2 through 4 0.05 / 0.1 / 0.2 / 0.3 / 0.5
above 1 through 2 0.001 / 0.002 / 0.01 / 0.05 / 0.1
above 0.5 through 1 0 / 0.001 / 0.002 / 0.01 / 0.05
above 0.05 through 0.5 0 / 0 / 0.001 / 0.002 / 0.01
0.05 or less All 0

Giants use mass bands and strength bands 1, 2 to 4, 5 to 7, 8 to 9 and 10 instead. A mass of exactly 500, 200 or 50 falls in the lower band.

Giant mass Magnitude multipliers by strength band
above 500 1.5, 2.5, 5, 10, 25
above 200 through 500 0.5, 1, 1.5, 2, 3
above 50 through 200 0.25, 0.5, 0.75, 1, 1.5
50 or less 0.1, 0.25, 0.5, 0.75, 1

These initial values are not ongoing radiation damage rules. System disasters covers later hazards.

Atmosphere, hydrosphere and climate

Section titled “Atmosphere, hydrosphere and climate”

An atmosphere starts at pressure 0. The temperature bands are above 400 K, above 150, above 50 and otherwise, and a value equal to a boundary belongs to the cooler band. Retention compares 0.02783 x BaseTemp / escape velocity² against 50, 35, 20 and 5 for those bands, and a strictly greater value loses the atmosphere. A d100 then selects the band’s first DIM_SetAtmosphere row whose cumulative MaxChance is at least the roll. Extreme tectonics, or Platelet Tectonics in the hottest band, adds sulphur gases. Sulphur dioxide fills the secondary slot when it is empty, or else the tertiary slot, and hydrogen sulphide fills the tertiary slot when it is still empty. With a primary and a secondary gas but no tertiary gas, a d1000 adds argon on 1 to 200, neon on 201 to 280 or helium on 281 to 300. If the tertiary slot is still empty, another d1000 adds chlorine on 1 to 60, fluorine on 61 to 95, bromine on 96 to 99 or iodine on 100.

With a primary gas present, pressure = mass x gravity x (6380 / radius)². A single gas gets 100%. A secondary gas splits it with a random gas percentage for the primary, 50 + 4d10 on d10 of 5 or less, 75 + 2d10 on 6 to 7 and 95 + d4 on 8 to 10. A tertiary gas divides the remaining percentage with another such roll for the secondary and takes the rest. When a tertiary gas is added, the secondary percentage changes but its stored partial pressure (GasAtm) keeps the earlier value. Percentage and partial pressure can disagree until the next refresh.

The initial hydrosphere uses BaseTemp with these constraints. Pressure 0, pressure below 0.006 with temperature above 245, or temperature above 369 gives None. Otherwise above 245 gives Liquid and 245 or less gives Ice Sheet. A None result still gets a one-in-five Ice Sheet fallback (d5 = 5) at BaseTemp of 223 or less and gravity of at least 0.1. Coverage rolls a coverage d10 and a percent d10. Inner-zone bodies outside the life zone add 1 to the coverage roll, capped at 10.

Coverage roll Radius below 2000 2000 to below 4000 4000 to below 6000 6000 or more
1 0 20 + d10 0 0
2 0 d10 d20 d20
3 d10 d20 20 + d10 20 + d20
4 10 + d10 10 + d10 30 + d10 40 + d20
5 10 + d10 20 + d10 40 + d10 60 + d10
6 20 + d10 20 + d10 50 + d10 70 + d10
7 20 + d10 30 + d10 60 + d10 80 + d10
8 30 + d10 40 + d10 70 + d10 90 + d5
9 30 + 3d10 50 + d10 80 + d10 95 + d5
10 10 + 9d10 50 + 4d10 90 + d10 100

Every d10 shown as a plain addition is the same percent die. Larger tiers generally allow more coverage, including 100%. In the 2000 to below 4000 tier, a coverage roll of 1 first gives 0 and is then overwritten by the rule for rolls 5 and 6, so it ends at 20 + d10. The optional cap applies after assignment, only to coverage above 70.

Albedo acts as a temperature multiplier. Each body rolls d10 plus a modifier and adds 0.01 to 0.10 from a second d10. In the inner zone the modifier is min(atmosphere bonus, ice bonus). The atmosphere bonus is +2 at pressure 0, -4 above 50 and -2 above 4. The ice bonus is -4 above 90% Ice Sheet coverage, -2 above 50% and 0 otherwise. Pressure 0’s +2 is therefore neutralised by an ice bonus of 0, while thick pressure and extensive ice give negative modifiers. Inner results below 2, 4, 7 and 10 give base albedo 0.75, 0.85, 0.95 and 1.05, and higher results give 1.15. In other zones pressure above 1 adds 1, and results below 4, 6, 8 and 10 give the same four bases, with 1.15 above. Evaporation and phase transitions mean the assigned coverage and composition need not match the environment finally displayed. The shared greenhouse and phase formulas are in terraforming.

The initial runaway greenhouse requires SurfaceTemp above 375 K and pressure above 0. Pressure multiplies by 10 + 2d10 for Dead tectonics, 10 + 4d10 for Hot Spot, 10 + 20d10 for Extreme and 10 + 10d10 otherwise. A result above 200 becomes 100 + d100. The hydrosphere is erased, albedo is rolled again, and the gases are replaced by 95 to 99% carbon dioxide (94 + d5) plus a nitrogen dioxide or sulphur dioxide remainder. A temperature refresh follows.

Moons and captured satellites

Section titled “Moons and captured satellites”

A positive explicit moon count overrides count selection, otherwise the satellite count roll runs. Queued captured types create moons first, then the ordinary count, and the survivors are numbered by distance. A count is a number of attempts, not guaranteed objects. Orbit placement comes before the physical radius is assigned.

Parents outside the inner zone get +5 on count rolls. A terrestrial parent first has a 1% twin chance (d100 = 50), which marks the parent with a twin companion flag and gives one moon. Otherwise d10 + zone bonus below 6, below 8, below 10, below 14 or otherwise gives 0, 1, d2, d5 or d10 moons. Giants give d10, d10 + 5, d10 + 10, d10 + 15 or d10 + 25 on the same bands, and the last band adds three independent 10% chances (d10 = 1) of an extra d10. A dwarf planet first sets 4 moons on d10 + bonus = 15 and 3 on a fresh roll of 14. A further fresh roll then always overwrites them. It gives 2 moons above 11, or otherwise another fresh roll gives 1 above 9 and 0 otherwise.

The orbit roll d9 gives a multiple of the parent radius. 1 to 4 give 1 + d1000 / 100, 5 to 6 give 6 + d1000 / 100, 7 to 8 give 16 + 3 x d1000 / 100, and 9 gives 45 + 3 x d1000 / 100. Distances are in km. A distance above the maximum satellite distance abandons creation at once with orbit 0, and no moon is made. Only spacing failures against sibling moons reroll. A separation equal to 3 x (new radius + sibling radius) is allowed. Placement happens before the new moon’s radius is rolled, so this test counts the new moon’s radius as 0, not its final radius.

Ordinary moon selection uses d100 plus abundance for giant parents, a further +1 for superjovians and -1 for gas giants with mass below 50. Dwarf parents cap the adjusted roll at 64, terrestrial parents at 94. Captured types and types set by another rule instead use the fixed-type profile and skip that selection. Their radii differ:

Ordinary adjusted roll Type Ordinary radius km Fixed-type radius km
below 65 Small Moon 10 x d10 10 x d10
65 to 85 Moon 100 x d10 100 x d10
86 to 94 Large Moon 1000 + 100 x d10 1000 + 100 x d10
95 to 98 Small Terrestrial moon 2000 + 100 x d10 2000 + 100 x d10, plus 1000 on d4 = 1
99 Small Terrestrial moon 3000 + 100 x d10 Same fixed-type Small Terrestrial recipe above
100 Terrestrial moon 3000 + 400 x d10 3000 + 100 x d10, plus 1000 on a coin flip
above 100 Terrestrial moon 4000 + 600 x d10 Same fixed-type Terrestrial recipe above

All ordinary radii outside the twin case are capped at parent radius / 4, keeping any fraction from that division. Fixed-type profiles have no such cap. The ordinary twin case instead stops early as a Terrestrial moon with radius whole part of (parent radius x (0.9 + d10 / 100)) and density = parent density x (0.95 + d10 / 100). It bypasses the cap and the ordinary density stages. Other profiles use density 0.3 + 0.1 x d10 in the inner zone and 0.1 + 0.05 x d10 elsewhere, plus 0.1 for a Terrestrial moon. Close moons of parents outside the inner zone with mass above 200 multiply density by 2 within 8 parent radii or by 1.5 within 12, provided the moon’s own twin companion flag is false.

A capture queues only a type based on the removed body’s radius. Below 1000 km it is a Moon, below 2000 a Large Moon, below 3000 a Small Terrestrial moon, and otherwise a Terrestrial moon. The later creation generates a new object and profile. It does not keep the captured body’s original atmosphere, minerals or exact radius.

Moon mass, gravity and escape velocity use the planet formulas. Year = sqrt((orbit / 398600)³ x 837 / (moon mass + parent mass)) x 24 hours, with the orbit in km. The Roche limit is 2.456 x (parent density / moon density)^0.33 x moon radius. A moon other than a Small Moon whose own twin companion flag is false becomes a Ring when it lies strictly inside that limit. Ordinary twin generation marks the parent and does not copy the flag to the new moon, so a twin moon is not exempt on that account. Tidal force = parent mass x 80 / (orbit / 375000)³, with the orbit in km, and above 7 the moon is locked. Base temperature copies the parent’s BaseTemp, not its greenhouse SurfaceTemp. Only Large Moons, Small Terrestrial moons and Terrestrial moons get an atmosphere and hydrosphere. Other moons get pressure 0, no hydrosphere and greenhouse factors of 1. All moons get albedo, temperature, the runaway check, minerals and terrain. Ruin and construct attempts require a Small Terrestrial or Terrestrial moon.

Asteroids, trojans and comets

Section titled “Asteroids, trojans and comets”

A belt’s starting mass budget uses d10 with a modifier of abundance, -1 at age above 7, then -1 in the inner zone or +2 elsewhere. If roll + modifier is below 8 the budget is 0.0001 x roll, otherwise 0.001 x roll, and the result is multiplied by 0.2. Belt density is 0.3 + 0.1 x max(1, d10 + abundance) in the inner zone and 0.1 + 0.1 x max(1, d10 + abundance) otherwise, with the same roll. Without an asteroid count set by another rule, the belt gets asteroids until the budget is 0 or less, and the last asteroid may overspend it. A positive count set by another rule ignores the budget.

A belt asteroid orbits at (centre - half-width) + half-width / 1000 x d2000, which spans centre plus or minus the half-width. On d20 = 10 it uses twice the width instead, at centre - 2 x half-width + half-width / 100 x d400. One in ten (d10 = 5) rolls eccentricity, and the others are circular. The radius multiplier is (d90 + 10) / 10. A d100 of 1 to 75, 76 to 90, 91 to 96, 97 to 99 or 100 multiplies it by 10, 20, 30, 50 or 100, with the fraction dropped. Asteroids have no atmosphere or hydrosphere, Dead tectonics and a magnetic field of 0. They do get physical gravity, a tidal day, temperature, albedo, minerals and terrain. The tidal day of an unlocked asteroid uses the dwarf and small moon hour bands, with no final multiplier.

The trojan factor t is mass^0.3333 rounded to the nearest whole number, with an exact half going to the even neighbour. Trojans appear on d500 below 10t, or with a positive count set by another rule. The count is d(5t) unless another rule sets it. The density roll d10 + abundance is clamped to 1 to 12, giving 0.3 + 0.1 x roll in the inner zone and 0.1 + 0.05 x roll elsewhere. Each trojan copies its parent’s eccentricity, direction and year, with an orbit factor of 1 + d400 / 10000 - 0.02 and a bearing near plus or minus 60 degrees with jitter from -9.999 through +10 degrees. Its parent is the giant planet even though its distance is measured in AU about the star.

Only a normally generated primary that is not a black hole creates comets automatically. With Minimum Comets per System (MinComets in FCT_Game) at 0 or less, d20 of 10 or less gives none. Otherwise the count is d2 on 12 or less, d3 on 13 to 14, d4 on 15 to 16, and d6, d8, d12 or d20 on 17, 18, 19 or 20. A positive minimum skips the early stop and raises the final count to the minimum.

A normal comet has radius 9 + d91 and density d60 / 100. On d50 = 50 the density is (40 + d40) / 100 and the radius 100 + d900, with an orbit penalty of 3. Within that case d5 = 5 gives radius 2000 + d6000, an orbit penalty of 7 and an eccentricity bonus of 7. It is still a comet. The orbit roll d10 - penalty below -2, below 1, below 5, below 8 or otherwise gives 50 + d250, 25 + d75, 15 + d35, 5 + d15 or 3 + d7 AU. That distance is multiplied by square root of stellar mass, with a minimum of 0.5 AU. The comet’s year uses (orbital distance / 2)³, unlike planets. Comets have no atmosphere or hydrosphere. A comet with radius below 2000 uses comet minerals, and one with radius of 2000 or more uses ordinary minerals. A ruin can appear at gravity above 0.4 on d100 at most the Ruin Generation Chance (NewRuinCreationChance in FCT_Game), without the normal temperature and distance tests.

Initial minerals and ground potential

Section titled “Initial minerals and ground potential”

Ordinary initial generation replaces the deposit list. Let R = max(radius, 100) and A = (abundance + 4) / 4.0, doubled inside the life zone. The outer d10000 succeeds at a roll of at most whole part of (A x (10 x density + R / 100) x 100). A failure ends the step after the deposits are cleared and before the ground potential changes. For each mineral ID 1 to 11, an inner d10000 must be strictly less than density x A x 30 x 100, where 30 is the ground survey base chance, doubled for Duranium. These thresholds are not capped. A successful amount is (d100 / 100.0 x R)², doubled for Duranium. The accessibility base is B = 1 - R / 2000 (R / 4000 for Duranium). Accessibility is B + d100 x (1 - B) / 100 rounded to one decimal (an exact half goes to the even neighbour) and clamped to 0.1 to 1. Amounts are decimals with no rounding to whole tons. Each deposit sets HalfOriginalAmount to amount / 2 and OriginalAcc to the current accessibility. The minerals are stored in FCT_MineralDeposit.

After a completed ordinary pass, a radius below 2500 sets the ground potential (GroundMineralSurvey) to Completed without a roll. At 2500 or more, d100 gives Completed on 1 to 80, Low on 81 to 90, Good on 91 to 96, High on 97 to 99 and Excellent on 100. Minimal is never chosen initially. The gas giant, comet and homeworld rules do not assign this potential. When a race performs a ground survey, the same rules run as later ground discovery instead of a fresh replacement. See ground surveys.

Gas giants roll d100 of at most 50, the gas giant Sorium chance. The die is rolled even when the deposit is guaranteed by the minor-race rule below, and the result is then ignored. They add only Sorium and do not clear existing deposits. Richness d10 of 1 to 4, 5 to 7, 8 to 9 or 10 gives an amount of die x actual radius, where the die is d10, d100, d1000 or d10000. Accessibility is 0.2 + 0.1 x d8. When a minor race is created in a system that has giants but none with Sorium, the first giant receives a guaranteed Sorium deposit.

The small comet rules clear deposits and use C = actual radius^(1/3). For each element, d3 = 1 skips it, and otherwise d15 of at most abundance + 4 succeeds. Richness d10 of 1 to 3, 4 to 7, 8 to 9 or 10 sums two d10000, two d15000, two d30000 or two d60000, then multiplies by C. Accessibility is 0.4 + d6 / 10. Duranium doubles its amount and gains 0.1 accessibility when it is 0.9 or less. Generated large comets use ordinary minerals, but Sol imports and mineral regeneration choose by comet type and always use the comet rules. Regeneration clears every body’s deposits first, then applies the giant rules to giants, the comet rules to comets and the ordinary rules to the rest.

Homeworld minerals replace the deposits, mark the body as a homeworld and always create all 11 elements. When the race is an NPR and the multiplier is exactly 1, the multiplier becomes 3. Richness d10 of 5 or less, 8 or less, or otherwise gives 50000 + 100 x d500, d1500 or d2500, times the multiplier. Accessibility is 0.1 x (d7 + 3). Duranium multiplies its amount by 3 and overwrites accessibility with 0.1 x (d2 + 8). Sorium multiplies its amount by 1.5 and overwrites accessibility with 0.1 x (d5 + 5). The overwritten accessibility dice are still rolled.

Ruins, constructs and special features

Section titled “Ruins, constructs and special features”

A ruin or construct attempt requires SurfaceTemp strictly between 200 and 360 K and gravity above 0.4. A first d100 of at most the Ruin Generation Chance (NewRuinCreationChance) attempts a ruin, but only when the body passes the 80 AU distance test below. A successful chance roll that fails the distance test does not go on to a construct. Only a failed ruin roll allows a second d100 below 4 to assign a type 1 construct, without the distance test.

Assigning a ruin does not repeat the suitability tests. It picks the first DIM_Ruin row whose cumulative MaxChance is at least d200, sets abandoned factories to FactoriesBase plus a die of FactoriesRandom sides, then sets the civilisation. The origin is the system the generation started from when there is one, and otherwise the current system. The first body found that has a ruin civilisation and lies in the origin system or a system directly linked to it supplies that civilisation, whatever any race has surveyed. Otherwise a new civilisation is generated, and d19 gives level 1 on 1 to 6, 2 on 7 to 12, 3 on 13 to 16, 4 on 17 to 18 and 5 on 19. A ruin without a construct separately has a 25% chance (d100 at most 25) of adding a type 1 construct.

The distance test also requires stellar or Lagrange connectivity. A body around the primary always passes the star part. A body around a companion passes when that companion, or for a deeper component its parent star, has an apoapsis within the limit, or when the primary and the companion, or its parent star, each have a Lagrange point on a planet whose apoapsis is within the limit. Then planets, asteroids and comets need a strict apoapsis below the limit, and moons need their parent’s orbital distance below the limit. Gas giant and superjovian planets never pass this test when it is used for ruins . The test is not just distance from the system primary.

A body that already has a construct gets no second one. Otherwise the construct takes the next ID, a research bonus of 1.2 + d8 / 10 (1.3 to 2.0) and a research field. Type 1 picks uniformly among fields 1 to 9 with d9. Types 2 and 3 use d4 over fields 1 to 4, with Missiles (field 4) replaced by Defensive Systems (field 7). A star with slots gets a 2% construct potential (d50 = 25) after slot filtering. The first terrestrial or dwarf planet initialised around it consumes the potential for a type 2 construct, without the normal ruin tests. The potential can stay unused.

After jump points are created, special features require race creation not skipped, a system other than Sol and no habitable-system request. A successful ordinary race creation earlier in the same generation marks race creation as skipped, which suppresses this whole block even when the request did not skip race creation. The count used below is the number of distinct systems other than Sol known to all non-NPR races together, not only to this explorer. The order matters:

  1. Rift. It counts as a special feature added to the system.
  2. Ruin defenders. For each ruin, d10 at most the count calls for defenders and counts as a special feature added to the system, even if no defenders result. This step runs even after a rift.
  5. Random wrecks. They need d10 = 5, whether or not a special feature was added. At least one wreck is attempted. Each further wreck follows with a probability of 50%, 40%, 30%, 20% and then 10% repeatedly, with no explicit cap on the number.

Outpost templates and the military AI of special races have their own pages. Later archaeology and construct operation are in salvage and archaeology.

Sol, homeworlds and setup overrides

Section titled “Sol, homeworlds and setup overrides”

Sol imports DIM_SolSystemBodies ordered by ParentBodyType and then BodyClass. The profiles supply radius, type, density, mass, gravity, hydrosphere, period and the other physical values. Bearings and eccentricity directions are random, as (d3600 - 1) / 10 degrees. A moon’s parent is found by planet number with orbit number 0. With Limited Planet Distance on, a Sol body with apoapsis above 80 AU rerolls its bearing until its current distance is below 80 AU. Sol bodies are imported with ground potential Completed. Giants, comets and Earth keep it. For the other bodies of 2500 km radius or more, the ordinary mineral rules draw it again whenever their deposit chance succeeds. Jupiter receives a Lagrange point.

Four named bodies get explicit atmospheres.

Body Gases, percentage and partial pressure in atm
Earth Nitrogen 79% (0.79), oxygen 20% (0.2), argon 1% (0.01)
Venus Carbon dioxide 96.5% (89.745), nitrogen 3.5% (3.255)
Mars Carbon dioxide 95.7% (0.005742), nitrogen 2.7% (0.000162), argon 1.6% (0.000096)
Titan Nitrogen 98.4% (1.4268), methane 1.4% (0.0203), hydrogen 0.2% (0.0029)

Sol ruins and minerals follow. Earth receives homeworld minerals with the Earth Mineral Deposits setting divided by 100 as its multiplier. Giants use the gas giant rules, comets the comet rules and other bodies the ordinary rules. Sol ruin chances bypass the ordinary tests. Mars has 5% (d100 below 6), Mercury 3% (d100 below 4), Titan and Ganymede 1% (d100 = 1), Io, Europa and Callisto 1/300 and Triton, Pluto and Eris 1/500.

With Add Planet X, Minerva orbits at outermost planet distance x (1.25 + d100 / 100). Its type roll is d100, with 1 to 10 terrestrial, 11 to 70 gas giant and 71 to 100 superjovian. Its special zone counts as inside the life zone, the hydrosphere cap is off, and the automatic gas giant Lagrange threshold is mass above 150 rather than the normal 200. Moons and trojans follow.

A habitable-system request first checks each star’s Lagrange connectivity at 80 AU. It then scans the planets and moons, other than giants, around the stars that pass. Component 1 passes that star check unconditionally. It does not need an actual Lagrange point on the primary. A planet must also have an orbital distance of at most 80 AU, while a moon is admitted at any parent distance. The rule is not a general parent orbit of at most 80 AU. The first body that passes the homeworld candidate test receives homeworld minerals. A system with no such body is removed and generation tries again.

The homeworld candidate test accepts a SurfaceTemp of 225 to 340 K inclusive before the rewrite, gravity of 0.5 to 2.5 inclusive, hydrosphere coverage of at least 20, eccentricity of at most 0.1 and no planet tidal lock. It clears the ruin, ruin civilisation and abandoned factories. It replaces the atmosphere with pressure 0.75 + d50 / 100, nitrogen 70 + d15 percent and oxygen for the remainder. It then refreshes evaporation, pressure and phase and checks a temperature of 225 to 340 K again. An NPR template with preferred terrains can add acceptance requirements. A rejection after the rewrite does not undo the changes. Homeworld selection covers the NPR use of this test.

Sol setup assigns a star disaster status (DisasterStatus in FCT_Star) only for warming, cooling or radiation at levels 1 to 3, and No Disaster otherwise. A Death Spiral choice stays in the Sol Disaster game setting (SolDisaster in FCT_Game) but gives the star no disaster here. No automatic supernova clock is started at this point. Ongoing effects and the explicit supernova trigger belong to system disasters and environmental hazards.

Randomness, identity and persistence

Section titled “Randomness, identity and persistence”

Generation draws from the game’s single shared random number generator, created once without a fixed seed. A die of N sides returns 1 to N, and a die of zero sides returns 0. Generation takes no seed and does not derive a separate generator for each system from SystemNumber or KnownSystemID. A system number identifies a slot and its connections. It does not make a system reproducible. Discarded dice, failed attempts, the order in which bodies are processed and setup retries all affect the sequence.

IDs are taken from the per-type counters before acceptance in several steps, so gaps in the IDs are expected. A save stores stars in FCT_Star, including luminosity, orbit and disaster status, bodies and their physical profiles in FCT_SystemBody, and atmospheres, deposits separately in FCT_AtmosphericGas, FCT_MineralDeposit . Loading a game rebuilds stars and bodies from these records. It does not regenerate them from a seed. Each race’s knowledge and body names stay in their own records. Object identity and reload covers the counters.

Worked examples

Section titled “Worked examples”
  • At mass 1, a first distance die of 4 gives 0.2 AU. A next die of 5 gives 0.2 x 1.6 + 0.1 = 0.42. Even if 0.2 is empty, the satellite allowance at 0.42 is (0.42 - 0.2) / 3 AU, not 0.42 / 3.
  • L = 1 gives an inner zone through 4 AU, an outer zone through 50 and a life zone from 0.75 to 1.4 inclusive. A body at 4 is inner but outside the life zone.
  • Radius 6380 and density 1 give mass 1, gravity 1 and escape velocity about 0.9984. At 1 AU around mass 1, the year of 8760 hours and BaseTemp of 255 K come before climate. The 255 is not necessarily the SurfaceTemp.
  • With an 80 AU limit, periapsis 70 and apoapsis 90 survive with the bearing rerolled until the current distance is below 80. Periapsis 80 and apoapsis 90 are removed.
  • Trojan t = 5 gives d500 below 50, which is 49 outcomes or 9.8%. A positive count set by another rule still uses up the d500 roll because the roll is made first.
  • Ordinary minerals at radius 1000, density 1, abundance 0 and outside the life zone have an outer threshold of 2000 (20%) and a conditional inner threshold of 3000 (29.99%), and 6000 (59.99%) for Duranium. An amount roll of 50 gives 250000 ordinary or 500000 Duranium.
  • A homeworld candidate can lose its ruins and gain oxygen and nitrogen, then fail the temperature check after the climate refresh. A rejection does not mean the body is unchanged.

Concept map

Section titled “Concept map”

Resources

Section titled “Resources”

Related community documentation and developer posts. These may describe a different game version.