apply tidal locking formulas to satellites

src/ts/alphaTestis.ts

@@ -83,7 +83,7 @@ const spaceStationModel = newSeededSpaceElevatorModel(0, [sunModel], systemCoord
     physicsViewer.showBody(landingpad.aggregate.body);
 }*/
 
-const moonModel = newSeededTelluricSatelliteModel(23, "Manaleth", [hecateModel]);
+const moonModel = newSeededTelluricSatelliteModel(23, "Manaleth", [hecateModel], [sunModel]);
 moonModel.physics.mass = 2;
 moonModel.physics.siderealDayDuration = 28 * 60 * 60;
 moonModel.physics.minTemperature = -180;

src/ts/planets/telluricPlanet/telluricSatelliteModel.ts

@@ -23,18 +23,24 @@ import { GenerationSteps } from "../../utils/generationSteps";
 import { Settings } from "../../settings";
 import { TelluricPlanetaryMassObjectPhysicsInfo } from "../../architecture/physicsInfo";
 import { Quaternion } from "@babylonjs/core/Maths/math";
-import { Axis } from "@babylonjs/core/Maths/math.axis";
 import { clamp } from "terrain-generation";
 import { getOrbitalPeriod, getPeriapsis, Orbit } from "../../orbit/orbit";
-import { hasLiquidWater } from "../../utils/physics";
+import { getCurrentUniverseYear, getTidalLockingTimescale, hasLiquidWater } from "../../utils/physics";
 import { CloudsModel, newCloudsModel } from "../../clouds/cloudsModel";
 import { TelluricPlanetaryMassObjectModel } from "./telluricPlanetaryMassObjectModel";
+import { StellarObjectModel } from "../../architecture/stellarObject";
+import { Lerp } from "@babylonjs/core/Maths/math.scalar.functions";
 
 export type TelluricSatelliteModel = TelluricPlanetaryMassObjectModel & {
     readonly type: OrbitalObjectType.TELLURIC_SATELLITE;
 };
 
-export function newSeededTelluricSatelliteModel(seed: number, name: string, parentBodies: CelestialBodyModel[]): TelluricSatelliteModel {
+export function newSeededTelluricSatelliteModel(
+    seed: number,
+    name: string,
+    parentBodies: CelestialBodyModel[],
+    parentStellarObjects: StellarObjectModel[]
+): TelluricSatelliteModel {
     const rng = getRngFromSeed(seed);
 
     const isSatelliteOfTelluric = parentBodies.some((parent) => parent.type === OrbitalObjectType.TELLURIC_PLANET);
@@ -59,6 +65,40 @@ export function newSeededTelluricSatelliteModel(seed: number, name: string, pare
         mass = Settings.EARTH_MASS * (radius / 6_371e3) ** 3;
     }
 
+    // Todo: do not hardcode
+    let orbitRadius = 2e9 + rng(GenerationSteps.ORBIT) * 15e9;
+
+    const orbitalP = 2; //clamp(normalRandom(2.0, 0.3, this.rng, GenerationSteps.Orbit + 80), 0.7, 3.0);
+
+    const parentMaxRadius = parentBodies.reduce((max, body) => Math.max(max, body.radius), 0);
+
+    orbitRadius = parentMaxRadius * clamp(normalRandom(2.0, 0.3, rng, GenerationSteps.ORBIT), 1.2, 3.0);
+    orbitRadius += parentMaxRadius * clamp(normalRandom(10, 4, rng, GenerationSteps.ORBIT), 1, 50);
+    orbitRadius += 2.0 * Math.max(0, parentMaxRadius - getPeriapsis(orbitRadius, orbitalP));
+
+    // this average is an approximation of a quaternion average
+    // see https://math.stackexchange.com/questions/61146/averaging-quaternions
+    const parentAverageAxialTilt: Quaternion = parentBodies.reduce((sum, body) => sum.add(body.physics.axialTilt), Quaternion.Zero());
+    parentAverageAxialTilt.scaleInPlace(1 / parentBodies.length);
+    parentAverageAxialTilt.normalize();
+
+    const parentMassSum = parentBodies.reduce((sum, body) => sum + body.physics.mass, 0);
+    const orbit: Orbit = {
+        radius: orbitRadius,
+        p: orbitalP,
+        period: getOrbitalPeriod(orbitRadius, parentMassSum),
+        orientation: parentAverageAxialTilt
+    };
+
+    const tidalLockingTimescale = getTidalLockingTimescale(parentMassSum, mass, orbitRadius, radius, 0);
+
+    const parentMaxBirthYear = parentStellarObjects.reduce((max, body) => Math.max(max, body.birthYear), 0);
+    const currentAge = getCurrentUniverseYear() - parentMaxBirthYear;
+
+    const tidalLockingFactor = Math.min(1, currentAge / tidalLockingTimescale);
+
+    const siderealDayDuration = Lerp(60 * 60 * 24, orbit.period, tidalLockingFactor);
+
     let pressure = Math.max(normalRandom(0.9, 0.2, rng, GenerationSteps.PRESSURE), 0);
     if (isSatelliteOfTelluric || radius <= 0.3 * Settings.EARTH_RADIUS) {
         pressure = 0;
@@ -69,16 +109,10 @@ export function newSeededTelluricSatelliteModel(seed: number, name: string, pare
     // when pressure is close to 1, the max temperature is close to the min temperature (the atmosphere does thermal regulation)
     const maxTemperature = minTemperature + Math.exp(-pressure) * randRangeInt(30, 200, rng, 81);
 
-    // this average is an approximation of a quaternion average
-    // see https://math.stackexchange.com/questions/61146/averaging-quaternions
-    const parentAverageAxialTilt: Quaternion = parentBodies.reduce((sum, body) => sum.add(body.physics.axialTilt), Quaternion.Zero());
-    parentAverageAxialTilt.scaleInPlace(1 / parentBodies.length);
-    parentAverageAxialTilt.normalize();
-
     const physicalProperties: TelluricPlanetaryMassObjectPhysicsInfo = {
         mass: mass,
         axialTilt: parentAverageAxialTilt,
-        siderealDayDuration: (60 * 60 * 24) / 10,
+        siderealDayDuration: siderealDayDuration,
         minTemperature: minTemperature,
         maxTemperature: maxTemperature,
         pressure: pressure,
@@ -88,25 +122,6 @@ export function newSeededTelluricSatelliteModel(seed: number, name: string, pare
 
     physicalProperties.oceanLevel = Settings.OCEAN_DEPTH * physicalProperties.waterAmount * physicalProperties.pressure;
 
-    // Todo: do not hardcode
-    let orbitRadius = 2e9 + rng(GenerationSteps.ORBIT) * 15e9;
-
-    const orbitalP = 2; //clamp(normalRandom(2.0, 0.3, this.rng, GenerationSteps.Orbit + 80), 0.7, 3.0);
-
-    const parentMaxRadius = parentBodies.reduce((max, body) => Math.max(max, body.radius), 0);
-
-    orbitRadius = parentMaxRadius * clamp(normalRandom(2.0, 0.3, rng, GenerationSteps.ORBIT), 1.2, 3.0);
-    orbitRadius += parentMaxRadius * clamp(normalRandom(10, 4, rng, GenerationSteps.ORBIT), 1, 50);
-    orbitRadius += 2.0 * Math.max(0, parentMaxRadius - getPeriapsis(orbitRadius, orbitalP));
-
-    const parentMassSum = parentBodies.reduce((sum, body) => sum + body.physics.mass, 0);
-    const orbit: Orbit = {
-        radius: orbitRadius,
-        p: orbitalP,
-        period: getOrbitalPeriod(orbitRadius, parentMassSum),
-        orientation: parentAverageAxialTilt
-    };
-
     // tidal lock
     physicalProperties.siderealDayDuration = orbit.period;
 

src/ts/starSystem/seededStarSystemModel.ts

@@ -146,7 +146,7 @@ export function newSeededStarSystemModel(seed: SystemSeed): StarSystemModel {
         for (let j = 0; j < nbMoons; j++) {
             const satelliteName = `${planetarySystemName}${Alphabet[j]}`;
             const satelliteSeed = centeredRand(planetarySystemRng, GenerationSteps.MOONS + j) * Settings.SEED_HALF_RANGE;
-            const satelliteModel = newSeededTelluricSatelliteModel(satelliteSeed, satelliteName, planets);
+            const satelliteModel = newSeededTelluricSatelliteModel(satelliteSeed, satelliteName, planets, stellarObjects);
             satellites.push(satelliteModel);
         }
     });