Yay velocity vectors work

src/main/kotlin/io/github/addoncommunity/galactifun/util/Constants.kt → src/main/kotlin/io/github/addoncommunity/galactifun/Constants.kt

@@ -1,4 +1,4 @@
-package io.github.addoncommunity.galactifun.util
+package io.github.addoncommunity.galactifun
 
 import org.bukkit.Location
 import org.bukkit.World
@@ -7,7 +7,7 @@ object Constants {
 
     const val KM_PER_LY = 9.461e12
     const val KM_PER_PC = 3.086e13
-    const val KM_PER_AU = 1.496e8
+    const val KM_PER_AU =  1.495978707e8
 
     const val GRAVITATIONAL_CONSTANT = 6.674e-11
     const val EARTH_GRAVITY = 9.81

src/main/kotlin/io/github/addoncommunity/galactifun/api/objects/CelestialObject.kt

@@ -1,10 +1,10 @@
 package io.github.addoncommunity.galactifun.api.objects
 
+import io.github.addoncommunity.galactifun.Constants
 import io.github.addoncommunity.galactifun.api.objects.properties.Orbit
 import io.github.addoncommunity.galactifun.units.Angle.Companion.degrees
 import io.github.addoncommunity.galactifun.units.Distance
 import io.github.addoncommunity.galactifun.units.Mass
-import io.github.addoncommunity.galactifun.util.Constants
 import io.github.addoncommunity.galactifun.util.LazyDouble
 import io.github.thebusybiscuit.slimefun4.libraries.dough.items.CustomItemStack
 import io.github.thebusybiscuit.slimefun4.utils.ChatUtils

src/main/kotlin/io/github/addoncommunity/galactifun/api/objects/PlanetaryObject.kt

@@ -1,5 +1,6 @@
 package io.github.addoncommunity.galactifun.api.objects
 
+import io.github.addoncommunity.galactifun.Constants
 import io.github.addoncommunity.galactifun.api.objects.properties.DayCycle
 import io.github.addoncommunity.galactifun.api.objects.properties.Orbit
 import io.github.addoncommunity.galactifun.api.objects.properties.OrbitPosition
@@ -9,7 +10,6 @@ import io.github.addoncommunity.galactifun.core.managers.PlanetManager
 import io.github.addoncommunity.galactifun.units.Distance
 import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
 import io.github.addoncommunity.galactifun.units.cos
-import io.github.addoncommunity.galactifun.util.Constants
 import io.github.seggan.kfun.location.plus
 import kotlinx.datetime.Instant
 import org.bukkit.Location

src/main/kotlin/io/github/addoncommunity/galactifun/api/objects/Star.kt

@@ -3,7 +3,7 @@ package io.github.addoncommunity.galactifun.api.objects
 import io.github.addoncommunity.galactifun.units.Distance
 import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
 import io.github.addoncommunity.galactifun.units.Mass
-import io.github.addoncommunity.galactifun.units.SphericalPosition
+import io.github.addoncommunity.galactifun.units.coordiantes.SphericalVector
 import kotlinx.datetime.Instant
 import org.bukkit.Material
 import org.bukkit.inventory.ItemStack
@@ -12,7 +12,7 @@ class Star(
     name: String,
     override val mass: Mass,
     override val radius: Distance,
-    val position: SphericalPosition
+    val position: SphericalVector
 ) : CelestialObject(name, ItemStack(Material.SUNFLOWER)) {
 
     override fun distanceTo(other: CelestialObject, time: Instant): Distance {

src/main/kotlin/io/github/addoncommunity/galactifun/api/objects/properties/Orbit.kt

@@ -4,12 +4,15 @@ import io.github.addoncommunity.galactifun.api.objects.CelestialObject
 import io.github.addoncommunity.galactifun.units.*
 import io.github.addoncommunity.galactifun.units.Angle.Companion.radians
 import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
+import io.github.addoncommunity.galactifun.units.coordiantes.CartesianVector
+import io.github.addoncommunity.galactifun.units.coordiantes.PolarVector
 import io.github.addoncommunity.galactifun.util.LazyDouble
 import kotlinx.datetime.Instant
-import org.joml.Vector2d
 import java.util.*
-import kotlin.math.acos
+import kotlin.math.atan2
 import kotlin.math.sqrt
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.seconds
 
 data class Orbit(
     val parent: CelestialObject,
@@ -26,6 +29,11 @@ data class Orbit(
         require(eccentricity < 1) { "Eccentricity must be less than 1" }
     }
 
+    val period: Duration by lazy {
+        val a = semimajorAxis.meters
+        (2 * Math.PI * sqrt(a * a * a / parent.gravitationalParameter)).seconds
+    }
+
     val meanMotion by LazyDouble {
         val a = semimajorAxis.meters
         sqrt(parent.gravitationalParameter / (a * a * a))
@@ -42,9 +50,11 @@ data class Orbit(
         return eccentricAnomalyCache.getOrPut(time) { kelpersEquation(meanAnomaly(time), eccentricity) }
     }
 
+    private val beta by LazyDouble { eccentricity / (1 + sqrt(1 - eccentricity * eccentricity)) }
+
     fun trueAnomaly(time: Instant): Angle {
-        val cosE = cos(eccentricAnomaly(time))
-        return acos((cosE - eccentricity) / (1 - eccentricity * cosE)).radians
+        val e = eccentricAnomaly(time)
+        return atan2(beta * sin(e), 1 - beta * cos(e)).radians * 2.0 + e
     }
 
     fun radius(time: Instant): Distance {
@@ -53,32 +63,26 @@ data class Orbit(
         return (a * (1 - eccentricity * cos(e))).meters
     }
 
-    val sinOmega by LazyDouble { sin(argumentOfPeriapsis) }
-    val cosOmega by LazyDouble { cos(argumentOfPeriapsis) }
-
-    fun velocityVectorAt(time: Instant): Vector2d {
-        val p = semimajorAxis.meters * (1 - eccentricity * eccentricity)
-        val h = sqrt(parent.gravitationalParameter * p)
-        val r = radius(time).meters
-        val nu = trueAnomaly(time)
-        val sinOmegaNu = sin(argumentOfPeriapsis + nu)
-        val cosOmegaNu = cos(argumentOfPeriapsis + nu)
+    fun position(time: Instant): PolarVector = PolarVector(radius(time), trueAnomaly(time))
 
-        val x = r * (cosOmega * cosOmegaNu - sinOmega * sinOmegaNu)
-        val y = r * (sinOmega * cosOmegaNu + cosOmega * sinOmegaNu)
+    private val deltaTimeForVelocity: Duration by lazy { period / 1e6 }
 
-        val magic = (h * eccentricity) / (r * p) * sin(nu)
-        val vx = x * magic - h / r * (cosOmega * sinOmegaNu + sinOmega * cosOmegaNu)
-        val vy = y * magic - h / r * (sinOmega * sinOmegaNu - cosOmega * cosOmegaNu)
-        return Vector2d(vx, vy)
+    fun velocity(time: Instant): CartesianVector {
+        // Do a tiny bit of calculus to find the velocity vector
+        val deltaTime = time + deltaTimeForVelocity
+        val pos1 = position(time)
+        val pos2 = position(deltaTime)
+        val w = eccentricAnomaly(time).degrees to eccentricAnomaly(deltaTime).degrees
+        val z = trueAnomaly(time).degrees to trueAnomaly(deltaTime).degrees
+        return (pos2.cartesian - pos1.cartesian) / deltaTimeForVelocity.doubleSeconds
     }
 
     companion object {
         /**
          * How much faster time is concerning orbital mechanics than in real life.
          * Minecraft is 72 times faster than real life, and a year is 12 times shorter than in real life.
          */
-        const val TIME_SCALE = 72.0 * 12.0
+        var TIME_SCALE = 72.0 * 12.0
 
         /**
          * A tiny eccentricity to use for otherwise circular orbits in order to avoid maths problems.

src/main/kotlin/io/github/addoncommunity/galactifun/base/BaseUniverse.kt

@@ -7,7 +7,7 @@ import io.github.addoncommunity.galactifun.units.Angle.Companion.radians
 import io.github.addoncommunity.galactifun.units.Distance.Companion.kilometers
 import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
 import io.github.addoncommunity.galactifun.units.Mass.Companion.kilograms
-import io.github.addoncommunity.galactifun.units.SphericalPosition
+import io.github.addoncommunity.galactifun.units.coordiantes.SphericalVector
 
 object BaseUniverse {
 
@@ -16,7 +16,7 @@ object BaseUniverse {
         mass = 1.989e30.kilograms,
         radius = 695700.0.kilometers,
         // The sun is at the center of the universe, yay!
-        position = SphericalPosition(0.0.radians, 0.0.radians, 0.0.meters)
+        position = SphericalVector(0.0.radians, 0.0.radians, 0.0.meters)
     )
 
     val earth = Earth()

src/main/kotlin/io/github/addoncommunity/galactifun/core/managers/PlanetManager.kt

@@ -1,6 +1,7 @@
 package io.github.addoncommunity.galactifun.core.managers
 
 import com.jeff_media.morepersistentdatatypes.DataType
+import io.github.addoncommunity.galactifun.Constants
 import io.github.addoncommunity.galactifun.api.objects.PlanetaryObject
 import io.github.addoncommunity.galactifun.api.objects.planet.PlanetaryWorld
 import io.github.addoncommunity.galactifun.api.objects.properties.DayCycle
@@ -11,7 +12,6 @@ import io.github.addoncommunity.galactifun.core.space.SpaceGenerator
 import io.github.addoncommunity.galactifun.pluginInstance
 import io.github.addoncommunity.galactifun.runOnNextTick
 import io.github.addoncommunity.galactifun.test.MarkerMock
-import io.github.addoncommunity.galactifun.util.Constants
 import io.github.addoncommunity.galactifun.util.getNearbyEntitiesByType
 import io.github.addoncommunity.galactifun.util.key
 import io.github.addoncommunity.galactifun.util.spawn

src/main/kotlin/io/github/addoncommunity/galactifun/serial/CollectionBlockStorageDataType.kt

@@ -1,6 +1,6 @@
 package io.github.addoncommunity.galactifun.serial
 
-import io.github.addoncommunity.galactifun.util.Constants
+import io.github.addoncommunity.galactifun.Constants
 import io.github.seggan.kfun.serial.BlockStorageDataType
 
 abstract class CollectionBlockStorageDataType<E, C : Collection<E>>(

src/main/kotlin/io/github/addoncommunity/galactifun/serial/MiscBlockStorageDataType.kt

@@ -1,6 +1,6 @@
 package io.github.addoncommunity.galactifun.serial
 
-import io.github.addoncommunity.galactifun.util.Constants
+import io.github.addoncommunity.galactifun.Constants
 import io.github.seggan.kfun.serial.BlockStorageDataType
 import kotlin.reflect.KClass
 

src/main/kotlin/io/github/addoncommunity/galactifun/units/Angle.kt

@@ -17,6 +17,9 @@ value class Angle private constructor(val radians: Double) : Comparable<Angle> {
     val milliarcseconds: Double
         get() = arcseconds * 1000
 
+    val standardForm: Angle
+        get() = Angle((radians % (2 * PI) + 2 * PI) % (2 * PI))
+
     companion object {
         const val DEGREES_PER_RADIAN = 180 / Math.PI
 

src/main/kotlin/io/github/addoncommunity/galactifun/units/Distance.kt

@@ -1,7 +1,6 @@
 package io.github.addoncommunity.galactifun.units
 
-import io.github.addoncommunity.galactifun.util.Constants
-import kotlin.math.abs
+import io.github.addoncommunity.galactifun.Constants
 
 @JvmInline
 value class Distance private constructor(val meters: Double) : Comparable<Distance> {
@@ -30,12 +29,8 @@ value class Distance private constructor(val meters: Double) : Comparable<Distan
         }
     }
 
-    init {
-        require(meters >= 0) { "Distance must be positive" }
-    }
-
     operator fun plus(other: Distance): Distance = Distance(meters + other.meters)
-    operator fun minus(other: Distance): Distance = Distance(abs(meters - other.meters))
+    operator fun minus(other: Distance): Distance = Distance(meters - other.meters)
     operator fun times(scalar: Double): Distance = Distance(meters * scalar)
     operator fun div(scalar: Double): Distance = Distance(meters / scalar)
     operator fun rem(scalar: Double): Distance = Distance(meters % scalar)

src/main/kotlin/io/github/addoncommunity/galactifun/units/coordiantes/CartesianVector.kt

@@ -0,0 +1,44 @@
+package io.github.addoncommunity.galactifun.units.coordiantes
+
+import io.github.addoncommunity.galactifun.units.Angle.Companion.radians
+import io.github.addoncommunity.galactifun.units.Distance
+import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
+import kotlin.math.atan2
+import kotlin.math.sqrt
+
+data class CartesianVector(
+    val x: Distance,
+    val y: Distance
+) {
+
+    val polar by lazy {
+        val theta = atan2(y.meters, x.meters).radians
+        PolarVector(length, theta)
+    }
+
+    val length by lazy {
+        sqrt(x.meters * x.meters + y.meters * y.meters).meters
+    }
+
+    operator fun plus(other: CartesianVector): CartesianVector {
+        return CartesianVector(x + other.x, y + other.y)
+    }
+
+    operator fun minus(other: CartesianVector): CartesianVector {
+        return CartesianVector(x - other.x, y - other.y)
+    }
+
+    operator fun times(scalar: Double): CartesianVector {
+        return CartesianVector(x * scalar, y * scalar)
+    }
+
+    operator fun div(scalar: Double): CartesianVector {
+        return CartesianVector(x / scalar, y / scalar)
+    }
+
+    fun distanceTo(other: CartesianVector): Distance {
+        val term1 = (x - other.x).meters
+        val term2 = (y - other.y).meters
+        return sqrt(term1 * term1 + term2 * term2).meters
+    }
+}

src/main/kotlin/io/github/addoncommunity/galactifun/units/coordiantes/PolarVector.kt

@@ -0,0 +1,31 @@
+package io.github.addoncommunity.galactifun.units.coordiantes
+
+import io.github.addoncommunity.galactifun.units.Angle
+import io.github.addoncommunity.galactifun.units.Distance
+import io.github.addoncommunity.galactifun.units.cos
+import io.github.addoncommunity.galactifun.units.sin
+
+data class PolarVector(
+    val radius: Distance,
+    val angle: Angle
+) {
+
+    val cartesian: CartesianVector by lazy {
+        CartesianVector(
+            x = radius * cos(angle),
+            y = radius * sin(angle)
+        )
+    }
+
+    operator fun times(scalar: Double): PolarVector {
+        return PolarVector(radius * scalar, angle * scalar)
+    }
+
+    operator fun div(scalar: Double): PolarVector {
+        return PolarVector(radius / scalar, angle / scalar)
+    }
+
+    fun distanceTo(other: PolarVector): Distance {
+        return cartesian.distanceTo(other.cartesian)
+    }
+}

src/main/kotlin/io/github/addoncommunity/galactifun/units/coordiantes/SphericalVector.kt

@@ -0,0 +1,27 @@
+package io.github.addoncommunity.galactifun.units.coordiantes
+
+import io.github.addoncommunity.galactifun.units.Angle
+import io.github.addoncommunity.galactifun.units.Distance
+import io.github.addoncommunity.galactifun.units.Distance.Companion.meters
+import io.github.addoncommunity.galactifun.units.cos
+import io.github.addoncommunity.galactifun.units.sin
+import org.joml.Vector3d
+
+data class SphericalVector(
+    val rightAscension: Angle,
+    val declination: Angle,
+    val distance: Distance
+) {
+
+    private val cartesianPosition by lazy {
+        val x = distance * sin(declination) * cos(rightAscension)
+        val y = distance * sin(declination) * sin(rightAscension)
+        val z = distance * cos(declination)
+        Vector3d(x.meters, y.meters, z.meters)
+    }
+
+    // What? I'm not afraid of a few trigonometric functions and a square root or two
+    fun distanceTo(other: SphericalVector): Distance {
+        return cartesianPosition.distance(other.cartesianPosition).meters
+    }
+}