[WIP] Falling leaves working

+ more cleanup
+ fix double-tinted leaves

src/main/kotlin/mods/betterfoliage/render/particle/FallingLeaves.kt

@@ -0,0 +1,132 @@
+package mods.betterfoliage.render.particle
+
+import mods.betterfoliage.config.Config
+import mods.betterfoliage.model.HSB
+import mods.betterfoliage.texture.LeafParticleKey
+import mods.betterfoliage.texture.LeafParticleRegistry
+import mods.betterfoliage.util.Double3
+import mods.betterfoliage.util.PI2
+import mods.betterfoliage.util.minmax
+import mods.betterfoliage.util.randomB
+import mods.betterfoliage.util.randomD
+import mods.betterfoliage.util.randomF
+import mods.betterfoliage.util.randomI
+import net.minecraft.client.Minecraft
+import net.minecraft.client.particle.IParticleRenderType
+import net.minecraft.util.math.BlockPos
+import net.minecraft.util.math.MathHelper
+import net.minecraft.world.World
+import net.minecraftforge.common.MinecraftForge
+import net.minecraftforge.event.TickEvent
+import net.minecraftforge.event.world.WorldEvent
+import net.minecraftforge.eventbus.api.SubscribeEvent
+import java.util.Random
+import kotlin.math.abs
+import kotlin.math.cos
+import kotlin.math.sin
+
+class FallingLeafParticle(
+    world: World, pos: BlockPos, leaf: LeafParticleKey, blockColor: Int, random: Random
+) : AbstractParticle(
+    world, pos.x.toDouble() + 0.5, pos.y.toDouble(), pos.z.toDouble() + 0.5
+) {
+
+    companion object {
+        @JvmStatic val biomeBrightnessMultiplier = 0.5f
+    }
+
+    var rotationSpeed = random.randomF(min = PI2 / 80.0, max = PI2 / 50.0)
+    val isMirrored = randomB()
+    var wasCollided = false
+
+    init {
+        particleAngle = random.randomF(max = PI2)
+        prevParticleAngle = particleAngle - rotationSpeed
+
+        maxAge = MathHelper.floor(randomD(0.6, 1.0) * Config.fallingLeaves.lifetime * 20.0)
+        motionY = -Config.fallingLeaves.speed
+
+        particleScale = Config.fallingLeaves.size.toFloat() * 0.1f
+        setColor(leaf.overrideColor?.asInt ?: blockColor)
+        sprite = LeafParticleRegistry[leaf.leafType][randomI(max = 1024)]
+    }
+
+    override val isValid: Boolean get() = (sprite != null)
+
+
+    override fun update() {
+        if (rand.nextFloat() > 0.95f) rotationSpeed *= -1.0f
+        if (age > maxAge - 20) particleAlpha = 0.05f * (maxAge - age)
+
+        if (onGround || wasCollided) {
+            velocity.setTo(0.0, 0.0, 0.0)
+            if (!wasCollided) {
+                age = age.coerceAtLeast(maxAge - 20)
+                wasCollided = true
+            }
+        } else {
+            val cosRotation = cos(particleAngle).toDouble(); val sinRotation = sin(particleAngle).toDouble()
+            velocity.setTo(cosRotation, 0.0, sinRotation).mul(Config.fallingLeaves.perturb)
+                .add(LeafWindTracker.current).add(0.0, -1.0, 0.0).mul(Config.fallingLeaves.speed)
+            prevParticleAngle = particleAngle
+            particleAngle += rotationSpeed
+        }
+    }
+
+    fun calculateParticleColor(textureAvgColor: Int, blockColor: Int) {
+        val texture = HSB.fromColor(textureAvgColor)
+        val block = HSB.fromColor(blockColor)
+
+        val weightTex = texture.saturation / (texture.saturation + block.saturation)
+        val weightBlock = 1.0f - weightTex
+
+        // avoid circular average for hue for performance reasons
+        // one of the color components should dominate anyway
+        val particle = HSB(
+            weightTex * texture.hue + weightBlock * block.hue,
+            weightTex * texture.saturation + weightBlock * block.saturation,
+            weightTex * texture.brightness + weightBlock * block.brightness * biomeBrightnessMultiplier
+        )
+        setColor(particle.asColor)
+    }
+
+    override fun getRenderType(): IParticleRenderType = IParticleRenderType.PARTICLE_SHEET_TRANSLUCENT
+}
+
+object LeafWindTracker {
+    var random = Random()
+    val target = Double3.zero
+    val current = Double3.zero
+    var nextChange: Long = 0
+
+    init {
+        MinecraftForge.EVENT_BUS.register(this)
+    }
+
+    fun changeWind(world: World) {
+        nextChange = world.worldInfo.gameTime + 120 + random.nextInt(80)
+        val direction = PI2 * random.nextDouble()
+        val speed = abs(random.nextGaussian()) * Config.fallingLeaves.windStrength +
+                (if (!world.isRaining) 0.0 else abs(random.nextGaussian()) * Config.fallingLeaves.stormStrength)
+        target.setTo(cos(direction) * speed, 0.0, sin(direction) * speed)
+    }
+
+    @SubscribeEvent
+    fun handleWorldTick(event: TickEvent.ClientTickEvent) {
+        if (event.phase == TickEvent.Phase.START) Minecraft.getInstance().world?.let { world ->
+            // change target wind speed
+            if (world.worldInfo.dayTime >= nextChange) changeWind(world)
+
+            // change current wind speed
+            val changeRate = if (world.isRaining) 0.015 else 0.005
+            current.add(
+                (target.x - current.x).minmax(-changeRate, changeRate),
+                0.0,
+                (target.z - current.z).minmax(-changeRate, changeRate)
+            )
+        }
+    }
+
+    @SubscribeEvent
+    fun handleWorldLoad(event: WorldEvent.Load) { if (event.world.isRemote) changeWind(event.world.world) }
+}