planetsim/BUILD.md
Jonas Reith 8cd487a5dc Civ Step 6: diplomacy, alliances & coalitions (save v22)
Wars stop being isolated 1-v-1 grudges. Each pair of nearby realms carries an
attitude that drifts over time, crystallising into alliances / non-aggression
pacts / rivalries. Allies don't fight and join each other's wars (coalitions),
and wars end in real peace treaties. Extends the Step-5 conflict subsystem
in place (same stepConflict tick, same war RNG), saved v22 + snapshotted.

- PlanetTypes.hpp: DiploKind + DiploTie {a,b capital indices, attitude, truceUntil,
  kind}; diplo* config knobs; WeatherSnapshot carries diplomacy.
- PlanetConflict.cpp: a diplomacy pass in stepConflict (revolts -> prosecute ->
  diplomacy -> declare). Attitude drifts from culture/faith affinity + a war
  penalty + truce recovery + per-pair noise; reclassified by threshold with
  hysteresis (kind-6 events on change). War-declare skips allied/non-aggression/
  truced pairs; hostility now rises as attitude falls (rivals fight); a defender's
  allies join by declaring their own war on the aggressor; a war end sets a truce
  + grudge. diploBetween/realmsAllied helpers.
- Save v22 + step-back: allegiance/wars block joined by a diplomacy block (new
  hasDiplo readState param + per-frame history block); captureWeather/restoreWeather
  carry the ties.
- Render: green alliance / dark-red rivalry great-circle arcs over the Territory
  view (P), per-realm ally/rival counts + active-wars list in the Realms tab, a
  cell-info allies/rivals line, kind-6 events (= icon).
- test_diplomacy.cpp: alliances/rivalries form, allies never war, coalitions form,
  truces after peace, determinism, RNG isolation, save-v22 + snapshot round-trip.
  All 14 suites green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-01 13:07:10 +02:00

392 lines
25 KiB
Markdown

# Planet Sim - World Creation
Fixed icosphere geometry; properties (elevation, plate, age, climate, biome) flow
over it. World creation runs as continuous, overlapping stages on a geological clock:
tectonics (boundary stress forms mountains/trenches) → continental drift & erosion →
hydrology (rivers/lakes) → climate (temperature/precipitation) → biomes → biota
(flora/fauna/funga). Initial
terrain forming is a generator (a couple hundred paced ticks, ~3 s, auto-pauses at
equilibrium), then drift/erosion/etc. continue. Press R to reseed, SPACE to pause.
(The eventual goal is a separate slow real-time "Live World" weather/life mode.)
## Build (Nobara / Linux)
Dependencies (raylib build needs these dev headers):
sudo dnf install cmake gcc-c++ mesa-libGL-devel libX11-devel \
libXrandr-devel libXinerama-devel libXcursor-devel libXi-devel \
wayland-devel libxkbcommon-devel
Then:
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j
./build/planetsim
raylib 5.5 is fetched automatically via CMake FetchContent.
OpenMP parallelizes the tectonic step (auto-detected by CMake; ships with
gcc, no extra package needed). It's optional -- without it the sim still runs,
serial. The step is memory-bandwidth-bound, so `OMP_NUM_THREADS=4` to `8` gives
the full ~2.8x speedup; the default uses all cores for no extra gain:
OMP_NUM_THREADS=6 ./build/planetsim
## Controls
LMB drag orbit camera (in the 3D view)
wheel zoom
hover show cell info (works in the 3D globe and the 2D map)
click open tile detail panel (subtiles grid, hoverable) + overlay
C close the detail panel
1 .. 7 color by elevation / plate / age / crust type / biome / temperature / precipitation
8 / 9 / 0 color by biota density: flora / fauna / funga
B toggle plate borders (on by default)
D toggle per-plate drift arrows + P<id> labels (on by default)
G toggle lat/lon graticule (+ degree numbers on the 2D map edges)
J toggle rivers (Phase 2.5 hydrology)
H start/stop Phase 2.5 (hydrology: rivers, lakes, fluvial erosion)
L generate biota population (flora/fauna/funga; settled world; re-press regenerates)
W enter / leave Live World (slow real-time clock; settled world)
N toggle the day/night terminator (Live World)
T toggle the tide-coloured coastline (Live World)
O toggle ocean-current arrows (warm = poleward/red, cold = equatorward/blue)
K toggle weather clouds/rain cover (Live World)
V toggle volcano markers (Live World; cones + eruption glow, build into islands)
M toggle place-name labels (names continents/oceans/ranges/rivers/lakes; Atlas tab)
E ecoregions colour view (names ecological provinces on first use; Eco tab)
I habitability heat map (where civilization can thrive)
U settlements: the dawn of civilization on first press, then toggle markers (Civ tab)
P territory / realms view + borders + war fronts + alliance/rivalry arcs (Realms tab)
X culture / faiths view + cultural borders (peoples/ethos/religion in the Cultures tab)
Y follow-cam: cycle the 3D camera through active storms (Live World; off after last)
. / , step the live clock forward / back by one rate-unit (auto-pauses; back also
rewinds weather + storms via an undo history)
wheel over the 2D map: zoom toward cursor (1-8x); drag pans when zoomed
SPACE pause while forming / re-evolve once settled (or the on-screen button)
[ / ] drift speed (My/s) -- in Live World: live clock rate (hours/s -> up to ~20 years/s)
S single tectonic tick (in Live World: step the clock forward, like '.')
F fast-forward Phase-1 forming to settled (instant)
R reseed planet (restart forming)
+ / - subdivision level (detail), 1..7
F5 / F9 save / load full state (planet.save)
F12 screenshot to screenshot.png
F2 reload planet.cfg (validated) and regenerate
CLI flags (applied before the first load/generate):
--seed N override the config seed
--config PATH use an alternate config file instead of planet.cfg
## Files (written in the working directory)
planet.cfg human-editable key=value config of every PlanetConfig parameter;
auto-created on first run, reload live with F2. Range-checked on
load; an invalid file reverts to safe defaults (not overwritten).
planet.save binary snapshot (versioned, currently v17: +geography/atlas; v16
+event log; v15 +stateful
volcanoes; v13 +Live World clock rate; v12 +step-back history
(~40 frames, so a load can rewind storms); v11 +weather systems/storms;
v10 +weather fields; v9 +moons; v8 +Live World clock; v7 +biota): seed + config + full planet state; F5
writes it, F9 reloads and resumes deterministically. As of v6
the config is stored as a self-describing key=value block (like
planet.cfg), so adding/removing config fields no longer breaks saves
(unknown keys ignored, missing keys default). v6 cannot load pre-v6
saves (one-time break) -- regenerate them.
## Config (planet.cfg, or PlanetConfig defaults in code)
radius 6.371e6 m (Earth) -- free to change
subdivisions 5 (~10k cells, ~223 km/cell)
plateCount 12
seaLevel 0 m
axialTilt 23.44 deg obliquity: leans the 3D globe + spin axis (visual; seasons later)
Tectonic tuning (also PlanetConfig): relief builds gradually toward an
isostatic equilibrium instead of saturating to the clamp.
continentBase 300 m resting elevation of continental crust
oceanBase -6000 m deep abyssal floor (oldest oceanic crust)
upliftGain 1.3e5 m/tick per unit convergence stress
beltWidth 3 cell-rings a mountain belt spreads inland
relax 0.02 isostatic relaxation toward base, per tick
Orogeny + seafloor (PlanetConfig): tall, persistent mountains and age-based
ocean depth. The orogeny boosts (collision/arc/persistence) are drift-only --
Phase 1 forms as before; tall mountains grow during Phase-2 drift.
collisionFactor 1.8 continent-continent uplift (Himalaya); raise = taller
arcFactor 1.4 continental subduction-arc uplift (Andes)
isostaticPersist 0.85 how strongly high crust resists relax (0..<1)
rootScale 2500 m above continentBase where persistence saturates
peakSoftCapStart 7000 m below this a tick's uplift always takes (P=1)
peakSoftCapEnd 12000 m at/above this uplift never takes (P=0); also the elev clamp
peakFailDrop 200 m max random drop when the grow roll loses (drift-only)
ridgeDepth -2500 m shallow elevation of brand-new crust at a ridge
seafloorSubsidence 280 m per sqrt(My): seafloor deepens with crustal age
seafloorSeedAge 80 My initial oceanic age spread at generation
Hydrology (PlanetConfig, Phase 2.5): macro drainage network + fluvial erosion.
Drift keeps running at a finer timestep during hydrology. (Config keys keep the
`phase3*` names for save/cfg compatibility; the UI labels this "Phase 2.5".)
phase3AfterMy 300 My drift before the "Start Phase 2.5?" prompt
phase3DtScale 0.2 hydrology timestep = cflDtMy()*this (finer = slower drift)
rainfall 1.0 uniform precip per cell (drainage-area unit)
riverThreshold 25 discharge above which a cell is a river (lower = richer network)
riverIncision 0.02 K in stream-power incision K*Q^m*S^n*dt (raise = carve faster)
riverDischargeExp 0.5 m (discharge exponent)
riverSlopeExp 1.0 n (slope exponent)
riverTransport 0.1 transport capacity coefficient (cap = this*Q*S)
depFrac 0.25 fraction of excess sediment deposited per cell
Biomes (PlanetConfig, Phase 3): per-cell biome classification thresholds. Temperature
= biomeEquatorTemp - biomePoleDrop*(|lat|/90)^biomeLatExp - biomeElevLapse*elevAbove.
biomeEquatorTemp 30 C temperature at the equator, sea level
biomePoleDrop 58 C equator->pole temperature drop
biomeLatExp 1.3 >1 keeps mid-latitudes temperate (cold concentrates at poles)
biomeElevLapse 0.006 C lost per metre above sea level
biomeIceTemp -9.5 C below -> Ice (polar caps + snowcaps); raise = bigger caps
biomeTundraTemp 2 C below (and above ice) -> Tundra/Taiga
biomeTaigaTemp 10 C cool + wet -> boreal forest
biomeSavannaTemp 22 C warm + moderate moisture -> savanna
biomeMountainElev 3000 m above sea level -> Mountains
biomeHillsElev 1200 m above sea level -> Hills
biomeBeachBand 60 m above sea level + adjacent ocean -> Beach
biomeLowlandElev 500 m wetlands only below this elevation
biomeWetlandMoist 0.72 moisture above this (low lowland) -> Wetland
biomeDesertMoist 0.28 moisture below this -> Desert
biomeGrassMoist 0.50 moisture below this -> Grassland/Savanna, else Forest
biomeTaigaMoist 0.40 cool + above this -> Taiga (else Tundra)
biomeLakeMinDepth 20 m filled-basin depth above sea level counting as a Lake
biomeSeasonWeight 0.6 winter temp weight in the Tundra/Taiga cutoffs (0 = annual mean only)
Seasons (PlanetConfig): axialTilt (above) drives per-cell summer/winter temps; color key 6
cycles temperature -> summer -> winter -> seasonality.
seasonAmpMax 18 C max seasonal half-range at full tilt/latitude/interior
seasonLatExp 1.2 latitude shape exponent (>1 pushes swing toward the poles)
seasonOceanFactor 0.15 ocean/coast seasonal-swing floor (thermal inertia)
seasonContinentRings 6 ocean-distance rings to reach full continentality (1 ~ 223 km)
Climate (PlanetConfig, Phase 3): temperature uses the biome* temp params above;
precipitation advects ocean moisture along zonal winds (windward rain, leeward rain
shadow, dry interiors) then diffuses it. Color modes 6 (temperature) / 7 (precipitation).
climateOceanMoisture 1.0 moisture air carries leaving the ocean (source)
climateRainEfficiency 0.5 fraction of available moisture*belt that rains per cell
climateOrographic 3.0 extra rain per unit normalized upslope (windward)
climateOroRefHeight 500 m upslope that counts as one orographic unit
climateContinentality 0.05 fractional moisture lost per inland cell (dries interiors)
climateWindPasses 50 moisture-advection iterations (steady state)
climateMoistureSmooth 12 precipitation diffusion passes (raise = smoother, more grass/forest)
climateCurrentFactor 4 C max coastal warming/cooling from ocean currents (0 = off; O shows arrows)
Biota (PlanetConfig): flora/fauna/funga. Density scalars drive color modes 8/9/0;
the discrete slot/point population is generated on demand (L) and saved (v7).
bioVegTempMin -5 C below this no plant growth
bioVegTempOpt 15 C at/above this temperature isn't limiting (flora)
bioVegMoistRef 0.5 normalized moisture where water isn't limiting (flora)
bioFaunaProductivity 0.9 herbivore carrying capacity per unit vegetation
bioCarnPreyMin 0.30 min local prey (fauna density) to support carnivores
bioCarnScale 1.0 carnivore weight ramp above the prey threshold
bioFungaMoistRef 0.4 normalized moisture where fungi aren't water-limited
bioFungaFloraWeight 0.6 how much fungi lean on flora (organic matter), 0..1
bioFungaTempMin -15 C above this fungi are not cold-limited (cold-tolerant)
bioRegionBonus 0.5 weight boost for archetypes present in same-biome neighbours
bioFloraSlots 12 max distinct flora per cell (point budget caps abundance)
bioFaunaSlots 10 max distinct fauna per cell
bioFungaSlots 8 max distinct funga per cell
bioFloraPoints 20 flora point budget at full density (scaled by density)
bioFaunaPoints 16 fauna point budget at full density
bioFungaPoints 14 funga point budget at full density
Live World (PlanetConfig): the slow real-time clock (hours -> weeks/months) over the
finished planet -- a moving day/night terminator, a live seasonal temperature cycle and a
moving snow line. axialTilt (above) drives the seasonal declination. Press W to enter.
dayLengthHours 24 hours in one planetary day (rotation -> day/night)
yearLengthDays 365.25 days in one planetary year (orbit -> seasons)
snowTemp 0 C land below the live temperature shows snow
seaIceTemp -2 C ocean below the live temperature shows sea ice
tideAmplitude 0.6 m equilibrium-tide scale per unit tide-raising weight
tideSunFactor 0.46 sun's tide weight relative to a unit moon (Earth ~0.46)
Moons (1-3, randomized in generateMoons() + saved v9): orbit on the live clock, raise the
tides with the sun, and render as small lit spheres with phases, orbit rings and eclipses.
Weather (PlanetConfig, Live World): a dynamic clouds/rain cycle on the live clock (key K),
saved v10. Evaporate over warm seas -> advect along the wind -> condense -> rain -> dissipate.
weatherEvapRate 0.4 /h ocean evaporation toward marine saturation
weatherWindKmh 45 km/h wind speed advecting humidity/cloud
weatherSatBase 0.4 air saturation at 0 C (lower = cloudier)
weatherSatTempCoef 0.025 saturation rise per +1 C
weatherCondense 0.6 /h supersaturation -> cloud
weatherOrographic 0.0009 extra condensation per m of windward upslope
weatherRainThresh 0.5 cloud cover above this rains
weatherRainRate 0.5 /h rain rate from excess cloud
weatherCloudDissip 0.12 /h cloud clearing
weatherSystemMax 8 max concurrent moving weather systems
weatherSpawnRate 0.06 /h genesis probability scale
weatherSystemSpeed 28 km/h drift speed of systems
weatherTropicalSST 26 C min sea-surface temp for tropical genesis
weatherSystemRadius 0.16 rad angular radius of a system's cloud/rain shield
weatherSystemCloud 1.2 /h cloud stamped at a system core
weatherSystemRain 1.6 /h rain at a system core
weatherHurricaneStr 0.6 strength above which a tropical system is a hurricane/typhoon
Live info tabs (Live World): the panel beside the 2D map has Sky, Tides, Weather and Events.
Events are a saved, capped journal (newest 200) for storm genesis/intensification, volcano
dormancy, eruptions and volcanic-island breaches; clicking an event selects and centres its cell.
Volcanoes (PlanetConfig, Live World, key V): placed by tectonic context on entering Live World,
then integrated as stateful lifecycle agents: grow, go dormant, explode, puff ash, and regrow
weaker. Step-back snapshots include volcano state. Saved v15+.
volcanoProbRidge 0.55 per-cell placement prob on a young spreading-ridge cell
volcanoProbBorder 0.06 per-cell placement prob on a normal plate-border cell
volcanoProbInterior 0.003 per-cell placement prob elsewhere (hotspots)
volcanoMaxCount 60 global cap (reservoir-sampled, ratios preserved)
volcanoBuildRate 0.02 m/h of growth at activity=1 while growing
volcanoFreeHeight 1000 m absolute height below which vents cannot go dormant
volcanoInitialBuildMax 2500 m max pre-built height when Live World starts
volcanoMaxHeight 3200 m built height where dormancy becomes certain
volcanoDormancyRate 1.0 per-year dormancy hazard scale above free height
volcanoDormantMinYears 120 minimum dormancy before explosion
volcanoDormantMaxYears 1200 maximum dormancy before explosion
volcanoExplodeDropFrac 0.20 fraction of built height shaved by explosion
volcanoActivityDecay 0.70 activity multiplier after each explosion
volcanoDeadActivity 0.05 growth stops at/below this activity
volcanoBlastRadius 0.09 radian radius of the instant explosion ash blast
volcanoBlastCloud 1.5 cloud cover added inside the blast
volcanoAshMinYears 0.5 minimum sustained ash emission after explosion
volcanoAshMaxYears 3.0 maximum sustained ash emission after explosion
volcanoAshPuffCellsPerWeek 2.0 average local cells puffed per week
volcanoAshCloud 0.9 cloud cover injected by sustained ash
volcanoAshCooling 6 C peak local cooling under an active ash plume
Geography / atlas (PlanetConfig, key M): extract + name geographic features from the frozen
terrain (continents, islands, oceans, seas, lakes, mountain ranges, peaks, rivers). Generated
once on a settled world, saved v17. The foundation of the civilization arc.
geoContinentMinCells 40 land component >= this many cells = Continent (else Island)
geoSeaMaxCells 60 ocean basin <= this many cells = Sea (else Ocean)
geoOceanSepRadians 1.4 min angular gap between ocean-basin centres (higher = fewer oceans)
geoOceanDeep 4 min rings from land for a cell to seed an ocean basin
geoMountainElev 2500 m min elevation for a mountain-range cell
geoRangeMinCells 4 min cells for a named mountain range
geoRiverMinDischarge 80 min mouth discharge for a named river
geoMaxRivers 40 cap on named rivers (largest by discharge)
geoMaxPeaks 40 cap on named peaks (highest)
Civilization (PlanetConfig, key U): settlements placed once on the best fertile cells, then their
population grows/declines on the Live World clock toward a food-driven carrying capacity. Saved v20.
civMaxSettlements 80 cap on settlement sites
civMinSpacingRadians 0.06 soft suppression scale around each pick (lower = tighter clusters)
civClusterExp 3.0 habitability weighting for placement (higher = clusters on the best land)
civMinHabitability 0.22 don't place a settlement below this habitability
civSeedPopulation 250 initial village population
civGrowthRate 0.02 logistic growth rate per year
civMaxPopulation 2e6 carrying capacity at habitability 1
civTownPop 5000 population at/above which a settlement is a Town
civCityPop 100000 population at/above which a settlement is a City
civAbandonPop 50 below this = abandoned/ruins (can revive)
civHabWaterWeight 0.45 habitability weight of water access (rivers/lakes/coast)
civHabFoodWeight 0.40 habitability weight of food (flora/fauna + ecoregion productivity)
civHabTempOpt 18 C most comfortable annual-mean temperature
civHabElevPenalty 2500 m high terrain steeply penalised above this
civSiteVariety 1.0 0 = flat city sizes; higher = big rivers/coasts host far larger cities
civGrowthMin 0.25 growth-rate floor at habitability 0 (rate scales with habitability)
civHarvestVar 0.25 year-to-year harvest swing (scaled by continentality)
civDroughtStrength 0.70 how hard a full drought cuts a region's carrying capacity
civDroughtPeriod 8 yr drought-noise epoch length (drought duration scale)
civDroughtThresh -0.15 drought-onset threshold (lower = rarer)
civDroughtArid 0.50 extra drought-proneness in arid regions
civColdYearStrength 0.50 crop loss in a rare cold year, x the cell's cold exposure
civFloodBonus 0.25 fertile-silt bonus on river cells (rare flood disaster)
civFamineRate 0.15 /yr accelerated population loss when food < population
civStormDeathRate 0.50 /yr deaths from a full-strength storm over a settlement
civHurricaneDeathMult 3.0 extra storm-death multiplier for a hurricane/typhoon
Territory & nations (PlanetConfig, key P derived from settlements, not saved): each settlement
projects a size-scaled influence range; nearby smaller towns become vassals of a larger capital
(a kingdom/empire), the rest are city-states; land cells inside a settlement's reach are its
territory, leaving wilderness frontiers between realms.
civTerritoryBase 0.035 rad base influence radius of any settlement
civTerritoryScale 0.05 rad extra reach per log10 of population (big cities reach far)
civTerritoryMax 0.35 rad cap on a single settlement's reach
civVassalRange 1.5 x a capital's range = how far it annexes towns into its realm
civEmpireMinMembers 5 settlements in a realm to count as an empire
civEmpirePop 5e6 total realm population to count as an empire
Conflict & war (PlanetConfig, save v21 stateful; shows on the Territory view P + Events/Realms tabs):
neighbouring realms grow hostile and fight; casualties shrink frontier cities; the winner conquers a
city (its allegiance flips) or sacks it (ruins); conquered foreign/distant cities revolt, so empires
rise and fall. Runs on the yearly Live-World tick.
warMaxConcurrent 6 cap on simultaneous active wars
warDeclareRate 0.12 war-declaration chance scale (x hostility)
warAmbition 1.0 hostility weight of the size gap (strong preys on weak)
warIdeology 0.8 hostility weight of culture + faith difference
warBorder 0.5 hostility weight of contested frontier
warWarlikeMult 1.4 military-strength bonus for a Warlike-ethos realm
warCasualtyRate 0.06 per war-year frontier-city population loss (loser more)
warConquerScore 0.6 |warscore| past which the winner takes a city
warSackChance 0.3 chance a taken city is razed to ruins instead of flipped
warExhaustion 1.5 |warscore| past which a war ends in peace (also a 60-yr cap)
warRevoltRate 0.04 per-year base revolt chance of a held foreign/distant city
warMinRealmPop 2000 realms below this population don't start wars
Diplomacy (PlanetConfig, save v22 on the Territory view P): realm-pair attitudes drift into alliances /
rivalries; allies never fight + join each other's wars (coalitions); wars end in truces. Runs in the same
yearly stepConflict tick; green arcs = alliances, dark-red arcs = rivalries.
diploDriftRate 0.06 per-year attitude change scale
diploAffinity 1.0 attitude pull from shared culture + faith (vs difference)
diploWarPenalty 0.5 extra per-year attitude drop while two realms are at war
diploTruceYears 12 post-war truce length (no new war between the two)
diploWarGrudge 0.4 one-off attitude drop when a war between them ends (a scar)
diploAllyThreshold 0.5 attitude at/above which two realms are allied
diploNonAggThreshold 0.2 attitude at/above which they sign a non-aggression pact
diploRivalThreshold -0.5 attitude at/below which they become rivals
Culture, beliefs & governments (key X derived from settlements + geography, not saved): settlements
on a continent share a culture (a people with an environment-driven ethos + a religion); each realm
gets a government type folded into its name (Republic of X / Duchy of X / X Theocracy / ...); realms
stay mono-cultural. No config knobs the ethos/faith/government rules are constants in
src/sim/PlanetCulture.cpp (computeCultures).
## Headless logic test (no display)
g++ -std=c++17 -O2 -Isrc/sim test_logic.cpp src/sim/IcoSphere.cpp \
src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp \
src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp \
src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp src/sim/PlanetLive.cpp \
src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp src/sim/PlanetVolcano.cpp \
src/sim/PlanetBiota.cpp \
src/sim/PlanetFloraGen.cpp src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp \
src/sim/NameGen.cpp src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp \
src/sim/PlanetCiv.cpp src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp \
src/sim/PlanetIO.cpp -o /tmp/t && /tmp/t
# Same source list for every suite: swap test_logic.cpp -> test_biota / test_live / test_ocean /
# test_weather / test_volcano / test_geography / test_ecoregions / test_civ / test_nation / test_culture / test_conflict / test_diplomacy.
# The CMake build also includes test_events for the viewer event journal.
Verifies geometry, plate assignment, gradual non-saturating relief and
determinism. Run after changing Planet::step().
## Notes for later phases
- Cell has a `subgrid` shared_ptr hook (null in phase 1) for the future
fine-resolution per-cell mesh (phases 4/5: civilization/culture).
- `neighbors` adjacency already built -> reuse for diffusion, climate,
cross-cell-boundary interaction.
- elevation is continuous meters (double); climate in phase 3 can read it
as a smooth function, not coarse bands.