Added general particle effects that follow a point of entity

src/main/java/com/minelittlepony/unicopia/client/URenderers.java

@@ -51,7 +51,7 @@ public interface URenderers {
         ParticleFactoryRegistry.getInstance().register(UParticles.UNICORN_MAGIC, createFactory(MagicParticle::new));
         ParticleFactoryRegistry.getInstance().register(UParticles.CHANGELING_MAGIC, createFactory(ChangelingMagicParticle::new));
         ParticleFactoryRegistry.getInstance().register(UParticles.RAIN_DROPS, createFactory(RaindropsParticle::new));
-        ParticleFactoryRegistry.getInstance().register(UParticles.HEALTH_DRAIN, createFactory(HealthDrainParticle::new));
+        ParticleFactoryRegistry.getInstance().register(UParticles.HEALTH_DRAIN, createFactory(HealthDrainParticle::create));
         ParticleFactoryRegistry.getInstance().register(UParticles.RAINBOOM_RING, RainboomParticle::new);
         ParticleFactoryRegistry.getInstance().register(UParticles.RAINBOOM_TRAIL, RainbowTrailParticle::new);
         ParticleFactoryRegistry.getInstance().register(UParticles.MAGIC_RUNES, RunesParticle::new);

src/main/java/com/minelittlepony/unicopia/client/particle/FollowingParticle.java

@@ -0,0 +1,76 @@
+package com.minelittlepony.unicopia.client.particle;
+
+import com.minelittlepony.unicopia.particle.FollowingParticleEffect;
+
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.particle.NoRenderParticle;
+import net.minecraft.client.particle.Particle;
+import net.minecraft.client.particle.SpriteProvider;
+import net.minecraft.client.world.ClientWorld;
+import net.minecraft.util.math.Vec3d;
+
+public class FollowingParticle extends NoRenderParticle {
+
+    private final FollowingParticleEffect parameters;
+
+    private final Particle particle;
+
+    private float scale;
+
+    public FollowingParticle(FollowingParticleEffect parameters, SpriteProvider provider, ClientWorld world, double x, double y, double z, double velocityX, double velocityY, double velocityZ) {
+        super(world, x, y, z, velocityX, velocityY, velocityZ);
+        this.scale = 0.1f * (this.random.nextFloat() * 0.5f + 0.5f) * 2.0f;
+        setMaxAge(3);
+        scale(0.125F);
+        this.parameters = parameters;
+        this.collidesWithWorld = false;
+        this.particle = parameters.getChildEffect().map(child -> MinecraftClient.getInstance().particleManager.addParticle(child, x, y, z, velocityX, velocityY, velocityZ)).orElse(null);
+    }
+
+    @Override
+    public Particle scale(float scale) {
+        this.scale *= scale;
+        super.scale(scale);
+        if (particle != null) {
+            particle.scale(scale);
+        }
+        return this;
+    }
+
+    @Override
+    public void move(double dx, double dy, double dz) {
+        super.move(dx, dy, dz);
+        if (particle != null) {
+            particle.setPos(x, y, z);
+        }
+    }
+
+    @Override
+    public void tick() {
+        if (this.particle == null || !this.particle.isAlive()) {
+            markDead();
+        }
+
+        super.tick();
+
+        Vec3d target = parameters.getTarget(world);
+        Vec3d pos = new Vec3d(x, y, z);
+
+        if (scale * 1.5F < 0.5F) {
+            scale(1.5F);
+        }
+
+        double distance = pos.distanceTo(target);
+        if (distance > 1) {
+            age = 0;
+        }
+
+        Vec3d motion = target.subtract(pos).normalize().multiply(Math.min(distance, parameters.getSpeed()));
+        move(motion.x, motion.y, motion.z);
+    }
+
+    @Override
+    public String toString() {
+        return super.toString() + ", Speed " + parameters.getSpeed() + ", Target (" + parameters.getTargetDescriptor() + ") Sub-Particle (" + particle + ")";
+    }
+}

src/main/java/com/minelittlepony/unicopia/client/particle/HealthDrainParticle.java

@@ -2,6 +2,7 @@ package com.minelittlepony.unicopia.client.particle;
 
 import com.minelittlepony.unicopia.particle.FollowingParticleEffect;
 
+import net.minecraft.client.particle.Particle;
 import net.minecraft.client.particle.ParticleTextureSheet;
 import net.minecraft.client.particle.SpriteBillboardParticle;
 import net.minecraft.client.particle.SpriteProvider;
@@ -12,7 +13,14 @@ public class HealthDrainParticle extends SpriteBillboardParticle {
 
     private final FollowingParticleEffect effect;
 
-    public HealthDrainParticle(FollowingParticleEffect effect, SpriteProvider provider, ClientWorld world, double x, double y, double z, double velocityX, double velocityY, double velocityZ) {
+    public static Particle create(FollowingParticleEffect effect, SpriteProvider provider, ClientWorld world, double x, double y, double z, double velocityX, double velocityY, double velocityZ) {
+        if (effect.getChildEffect().isPresent()) {
+            return new FollowingParticle(effect, provider, world, x, y, z, velocityX, velocityY, velocityZ);
+        }
+        return new HealthDrainParticle(effect, provider, world, x, y, z, velocityX, velocityY, velocityZ);
+    }
+
+    protected HealthDrainParticle(FollowingParticleEffect effect, SpriteProvider provider, ClientWorld world, double x, double y, double z, double velocityX, double velocityY, double velocityZ) {
         super(world, x, y, z, velocityX, velocityY, velocityZ);
         setSprite(provider);
         setMaxAge(3);

src/main/java/com/minelittlepony/unicopia/particle/FollowingParticleEffect.java

@@ -1,6 +1,7 @@
 package com.minelittlepony.unicopia.particle;
 
 import java.util.Locale;
+import java.util.Optional;
 
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
@@ -25,12 +26,23 @@ public class FollowingParticleEffect implements ParticleEffect {
 
     private final float followSpeed;
 
+    private Optional<ParticleEffect> childEffect = Optional.empty();
+
     protected FollowingParticleEffect(ParticleType<FollowingParticleEffect> type, StringReader reader) throws CommandSyntaxException {
         this(type, -1, ParticleFactoryHelper.readVector(reader), ParticleFactoryHelper.readFloat(reader));
+
+        if (reader.canRead()) {
+            reader.expect(' ');
+            childEffect = ParticleFactoryHelper.read(reader);
+        }
     }
 
-    protected FollowingParticleEffect(ParticleType<FollowingParticleEffect> particleType, PacketByteBuf buf) {
+    protected FollowingParticleEffect(ParticleType<FollowingParticleEffect> type, PacketByteBuf buf) {
-        this(particleType, buf.readInt(), new Vec3d(buf.readDouble(), buf.readDouble(), buf.readDouble()), buf.readFloat());
+        this(type, buf.readInt(), new Vec3d(buf.readDouble(), buf.readDouble(), buf.readDouble()), buf.readFloat());
+
+        if (buf.readBoolean()) {
+            childEffect = ParticleFactoryHelper.read(Registry.PARTICLE_TYPE.get(buf.readInt()), buf);
+        }
     }
 
     public FollowingParticleEffect(ParticleType<FollowingParticleEffect> type, Vec3d target, float followSpeed) {
@@ -51,6 +63,22 @@ public class FollowingParticleEffect implements ParticleEffect {
         this.followSpeed = followSpeed;
     }
 
+    public ParticleEffect withChild(ParticleEffect child) {
+        childEffect = Optional.of(child);
+        return this;
+    }
+
+    public Optional<ParticleEffect> getChildEffect() {
+        return childEffect;
+    }
+
+    public String getTargetDescriptor() {
+        if (movingTarget > -1) {
+            return "Moving(" + movingTarget + ")";
+        }
+        return fixedTarget.toString();
+    }
+
     public Vec3d getTarget(World world) {
         if (movingTarget > -1) {
             Entity e = world.getEntityById(movingTarget);
@@ -79,10 +107,26 @@ public class FollowingParticleEffect implements ParticleEffect {
         buf.writeDouble(fixedTarget.y);
         buf.writeDouble(fixedTarget.z);
         buf.writeFloat(followSpeed);
+        getChildEffect().ifPresentOrElse(child -> {
+            buf.writeBoolean(true);
+            buf.writeInt(Registry.PARTICLE_TYPE.getRawId(child.getType()));
+            child.write(buf);
+        }, () -> buf.writeBoolean(false));
     }
 
     @Override
     public String asString() {
-        return String.format(Locale.ROOT, "%s %.2f %.2f %.2f %.2f", Registry.PARTICLE_TYPE.getId(getType()), fixedTarget.x, fixedTarget.y, fixedTarget.z, followSpeed);
+        return getChildEffect().map(child -> {
+            return String.format(Locale.ROOT, "%s %.2f %.2f %.2f %.2f %s",
+                    Registry.PARTICLE_TYPE.getId(getType()),
+                    fixedTarget.x, fixedTarget.y, fixedTarget.z,
+                    followSpeed, child.asString());
+        }).orElseGet(() -> {
+            return String.format(Locale.ROOT, "%s %.2f %.2f %.2f %.2f",
+                    Registry.PARTICLE_TYPE.getId(getType()),
+                    fixedTarget.x, fixedTarget.y, fixedTarget.z,
+                    followSpeed);
+        });
+
     }
 }

src/main/java/com/minelittlepony/unicopia/particle/ParticleFactoryHelper.java

@@ -1,8 +1,11 @@
 package com.minelittlepony.unicopia.particle;
 
+import java.util.Optional;
+
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 
+import net.minecraft.command.argument.ParticleEffectArgumentType;
 import net.minecraft.network.PacketByteBuf;
 import net.minecraft.particle.ParticleEffect;
 import net.minecraft.particle.ParticleType;
@@ -10,6 +13,16 @@ import net.minecraft.util.math.Vec3d;
 
 public interface ParticleFactoryHelper {
 
+    @SuppressWarnings("unchecked")
+    static <T extends ParticleEffect> Optional<T> read(StringReader reader) throws CommandSyntaxException {
+        return Optional.ofNullable((T)ParticleEffectArgumentType.readParameters(reader));
+    }
+
+    @SuppressWarnings("deprecation")
+    static <T extends ParticleEffect> Optional<ParticleEffect> read(ParticleType<T> type, PacketByteBuf buf) {
+        return Optional.ofNullable(type.getParametersFactory().read(type, buf));
+    }
+
     static Vec3d readVector(StringReader reader) throws CommandSyntaxException {
         return new Vec3d(readDouble(reader), readDouble(reader), readDouble(reader));
     }