traveller-worldgen

A command-line generator for single Traveller worlds. Given a seed, it rolls a world's Universal World Profile (UWP) — starport, size, atmosphere, hydrographics, population, government, law level, tech level — plus its bases and a generated name.

The repo is organized to hold each edition of Traveller's world generation side by side. Today that is Classic Traveller (Book 3: Worlds and Adventures, GDW 1977) in classic/, MegaTraveller (Referee's Manual, DGP/GDW 1987) in megatraveller/, Traveller: The New Era (GDW 1993) in tne/, and Traveller5 (Core Book 3, FFE 5.10) in t5/; further editions (Mongoose, …) are added as sibling packages sharing the same dice and ehex foundation.

MegaTraveller extends the classic profile with a referee-chosen subsector nature (which shapes the starport), a non-imperial military base, derived trade classifications, and the two system-level counts on its generation flowchart — gas giants and planetoid belts. TNE shares MegaTraveller's nature-driven starport and military base but has no trade or system-count layer, so a TNE world is a UWP plus bases.

Traveller5 is the outlier: its core draw is Flux (1D − 1D, −5…+5) rather than the 2D − 7 of the other three, hydrographics keys off atmosphere instead of size, and characteristics are hard-capped. On top of the UWP, T5 generates Naval/Scout bases, the PBG counts (population digit, planetoid belts, gas giants), trade classifications, and the Ix/Ex/Cx extensions (Importance, Economic, Cultural).

Usage

Each edition is a subcommand:

worldgen <edition> [flags]
worldgen classic [-seed N] [-format text|uwp|json] [-n COUNT]
worldgen mega    [-seed N] [-format text|uwp|json] [-n COUNT] [-nature NATURE]
worldgen tne     [-seed N] [-format text|uwp|json] [-n COUNT] [-nature NATURE]
worldgen t5      [-seed N] [-format text|uwp|json] [-n COUNT]

Run worldgen with no arguments to list editions. Flags shared by every edition:

• -seed N — seed for reproducibility (omitted → time-based, and the drawn seed is printed to stderr so the run can be replayed).
• -format — text (default), uwp, or json.
• -n COUNT — generate COUNT independent worlds (default 1). A single seed reproduces the whole batch.

MegaTraveller and TNE add:

• -nature — subsector nature selecting the starport column: backwater, standard (default), mature, or cluster.

Examples

$ go run ./cmd/worldgen classic -seed 42
Draejapu  X200346-2  None
  Starport      X  No starport; no provision for starship landings
  Size          2  2,000 miles diameter
  Atmosphere    0  No atmosphere
  Hydrographics 0  No free standing water
  Population    3  1,000
  Government    4  Representative Democracy
  Law Level     6  Most firearms (all except shotguns) prohibited; 6+ to avoid arrest
  Tech Level    2  Halberd, Broadsword · Cannon · Wind

$ go run ./cmd/worldgen classic -seed 1977 -n 4 -format uwp
Horou          C674474-9  S
Peimern        E7A5431-5  —
Nojeis         C110875-A  S
Houreir        C250555-9  —

$ go run ./cmd/worldgen classic -seed 42 -format json
{
  "name": "Draejapu",
  "uwp": "X200346-2",
  ...
}

$ go run ./cmd/worldgen mega -seed 42
Pupijou  X200346-2  None
  Starport      X  None; no starport
  Size          2  Small (3,200 km, Luna)
  Atmosphere    0  Vacuum
  Hydrographics 0  Desert World (0–4%)
  Population    3  Low (thousands)
  Government    4  Representative Democracy
  Law Level     6  Moderate law (all firearms except shotguns prohibited); 6+ to avoid arrest
  Tech Level    2  Pre-Industrial (printing press)
  Trade         Lo Ni Va
  Gas Giants    5
  Belts         1

$ go run ./cmd/worldgen mega -seed 1977 -n 4 -format uwp
Paedrucil      C645856-7  SM  G3  -   -
Niagaevei      B452452-B  N   G3  -   Ni Po
Voupaher       C748754-9  -   -   -   Ag
Daehia         E787645-5  -   G4  B1  Ag Ni Ri

$ go run ./cmd/worldgen tne -seed 1977 -n 4 -format uwp
Robriheil      C645856-7  SM
Sihir          B675453-A  —
Tifeifarn      C496333-5  S
Liafufous      A83A336-D  N

$ go run ./cmd/worldgen t5 -seed 42
Saejiarn  X223300-3  None
  Starport      X  None; no starport
  Size          2  2,000 miles (3,200 km)
  Atmosphere    2  Very Thin, Tainted
  Hydrographics 3  30% Water
  Population    3  Thousands (10^3)
  Government    0  No Government Structure
  Law Level     0  No Law. No prohibitions
  Tech Level    3  Pre-Industrial (basic science)
  Trade         Lo Po
  Importance    {-3}
  Economic      (620+1)  (RU 12)
  Cultural      [2161]
  Gas Giants    2
  Belts         3

$ go run ./cmd/worldgen t5 -seed 1977 -n 4 -format uwp
Cirisould      C623468-A  -  {+0} (A33+3) [648C]  130  Ni Px Po
Faedoth        B486899-7  S  {+1} (978+2) [A914]  821  Ph Pa Ri
Mumeil         B221244-D  S  {+1} (B11-3) [434D]  201  Lo Po
Niadreicoun    B898200-7  -  {-1} (310+1) [5188]  701  Lo

The uwp base column is a compact code. Classic: N naval, S scout, NS both, — none. MegaTraveller and TNE: N naval, S scout, A naval + scout, plus a trailing M for a non-imperial military base. The MegaTraveller line then carries a gas-giant marker (Gn), a planetoid-belt marker (Bn), and the trade codes (- for an empty field); TNE's line ends at the base code (— when none). Traveller5 uses N/S/A bases (- when none), then the extensions {Ix} (Ex) [Cx], the three-digit PBG, and the trade codes.

Layout

Shared foundation (edition-independent):

• dice/ — the Roller interface (Seeded, Scripted, Fixed) and D6(n).
• ehex/ — Traveller extended-hex digit Encode/Decode.

Per-edition rules (each self-contained, sharing dice and ehex):

• classic/ — Classic Traveller Book 3: tables, the tech-index DM matrix, world generation, descriptions, and the name generator.
• megatraveller/ — MegaTraveller Referee's Manual: the same shape plus the nature-driven starport table, bases (incl. military), trade classifications, gas giants, and planetoid belts.
• tne/ — Traveller: The New Era: MegaTraveller's UWP generation (nature-driven starport, military base) minus the trade and gas-giant layers.
• t5/ — Traveller5 Core Book 3: the Flux-based UWP, Naval/Scout bases, PBG counts, trade classifications, and the Ix/Ex/Cx extensions.
• future — mongoose/, … as sibling packages.

CLI and docs:

• cmd/worldgen/ — the CLI. main.go dispatches on an edition subcommand; each edition has its own runner file (classic.go, megatraveller.go, tne.go, t5.go) registered in the editions map.
• docs/<edition>/ — the verified rules extract (world-generation.md), plus the source PDF(s) as a local symlink you supply yourself. The PDFs are copyrighted Far Future Enterprises material, so docs/*/*.pdf is gitignored — verifying a table against source requires your own copy, but nothing in the repo depends on the PDF being present.

Adding an edition means: a new rules package (e.g. mongoose/), a cmd/worldgen/<edition>.go runner, and one entry in the editions map. The rules packages stay deliberately independent (duplication over premature abstraction), but the CLI scaffolding is shared: a generic runEdition[T] owns the flag parse / seed / generate / write flow, and renderWorlds[T] / renderWorldsJSON[T] own output formatting — so a runner supplies only its edition-specific flags, generator, and per-world formatters. A cross-edition Generator interface over the rules packages is still not defined; it hasn't earned one.

Development

task          # gofumpt + go vet + golangci-lint + go test -race
task test     # tests only
task fmt      # apply gofumpt

Golden CLI outputs live in cmd/worldgen/testdata/; regenerate them with go test ./cmd/worldgen -update after an intentional output change.

Rules & provenance

Each edition's rules and tables are transcribed from docs/<edition>/world-generation.md, an extraction verified cell-by-cell against the source PDF(s).

Classic (Book 3)

Clamping. Book 3 floors negative dice-modifier results at 0 but specifies no upper bounds. This generator floors every characteristic at 0 and otherwise keeps the rolled value, rendering it in extended hex — so atmosphere, government, law level, and tech level may all exceed their last described table row. The sole upper cap is hydrographics at A (100% water), a real physical ceiling. Keeping the other values raw matches the source: the Book 3 tech-index matrix itself defines DMs for atmosphere D and E, and law level is deliberately derived from the true (uncapped) government so both digits stay consistent.

Describing out-of-range values. Atmosphere, government, and tech level have no Book 3 guidance past their tables, so a value beyond the last row is reported as "(beyond described range)". Law level is the exception: Book 3's note makes each level cumulative and ties the raw level to an enforcement throw, so the text output always shows the weapons prohibition plus the saving throw to avoid arrest (N+, equal to the law level). A law level above 9 keeps level 9's prohibition while the throw keeps rising — becoming impossible to make (and thus certain arrest) at 13+.

MegaTraveller (Referee's Manual)

Complete ranges. Unlike Book 3, MegaTraveller describes every value the dice can produce (government/atmosphere 0–F, law/tech 0–L), so nothing is ever "beyond described range." Hydrographics is still capped at A.

Source corrections. Two printed-table errors were resolved against the manual's own text and recorded in the doc: the Technology-DM table prints Starport A as +8, but its stated maximum adjusted roll of 20 reconciles only at +6 (the value used); and the trade-classification atmosphere ranges for Industrial (2–4,7,9) and Rich (6,8) were corrected from an earlier reconstruction.

Deferred. The Basic Mainworld Generation flowchart has no bases step and the sources give no throw that promotes a scout base to a Way Station, so base code B is deferred — the generator emits N/S/A/M. Gas giants and planetoid belts (the flowchart's two system-level counts) are generated; the fuller Extended System Generation (stars, orbits, satellites, additional planets), travel zones, and allegiance remain out of scope.

TNE (The New Era)

Source. The World Tamer's Handbook (which prompted this edition) turned out not to contain the core UWP generation — its Stars & Planets chapter defers to "pages 192–195 of the TNE rulebook." So the tables come from the TNE core rulebook (Basic Mainworld Generation, printed pp. 186–190); the WTH's "Detailing Planets" physical layer is out of scope.

Near-identical to MegaTraveller. TNE's UWP generation matches MegaTraveller's almost exactly — same starport-by-nature table, formulas, and bases. It notably prints Starport A tech-DM +6, confirming the value MegaTraveller misprints as +8. The only rules differences: the tech-DM matrix adds Starport F +1 and Government E/F −1, and TNE has no trade-classification or gas-giant step.

Deferred. TNE's Planetary-Density → surface-gravity step (part of world size) and the WTH detail layer (temperature, atmospheric composition, world mass) are physical data beyond the UWP, out of scope.

Traveller5 (Core Book 3)

A different engine. T5's core draw is Flux (1D − 1D, −5…+5), not 2D − 7. Atmosphere is Flux + Size, hydrographics is Flux + Atmosphere (keyed off atmosphere, not size), government/law are Flux-based, and every characteristic is hard-capped (Size/Atm/Gov 0–F, Law 0–J, Hyd 0–A) — so nothing is ever "beyond described range." The starport table is a single 2D column identical to Classic; bases roll 2D ≤ target (T5's N− notation), the mirror of Classic's ≥.

Extensions. Beyond the UWP, T5 generates the Ix (Importance, {±n}), Ex (Economic, (RLI±E) with derived Resource Units), and Cx (Cultural, [HASS]) extensions, plus the PBG counts and trade classifications.

Source note. Core Book 3 p. 25 gives the tech-level DM formula but no prose TL table, so the era-band descriptions reuse the edition-invariant Traveller TL bands. Book 3 states no As→Va suppression rule, so an asteroid belt carries both.

Deferred. MainWorld-type (planet vs. satellite), Habitable-Zone/Climate and the climate trade codes that depend on it, the Secondary/Political/Special trade codes (referee-assigned), Nobility/Allegiance/Travel-Zone/Native-Intelligent-Life (the rest of NABZ-NIL), Depot/Way-Station bases, and the whole system map are out of scope for a bare mainworld generator.