Smoothly animate the spinning of the crystal heart

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

@@ -17,25 +17,7 @@ public class CloudsEscapingParticle extends GroundPoundParticle {
     }
 
     @Override
-    public void tick() {
+    public void spawnChildParticles() {
-        this.prevPosX = this.x;
-        this.prevPosY = this.y;
-        this.prevPosZ = this.z;
-        if (this.age++ >= this.maxAge) {
-           this.markDead();
-        } else {
-           this.velocityY -= 0.04D * this.gravityStrength;
-           this.move(this.velocityX, this.velocityY, this.velocityZ);
-           this.velocityX *= 0.9800000190734863D;
-           this.velocityY *= 0.9800000190734863D;
-           this.velocityZ *= 0.9800000190734863D;
-           if (this.onGround) {
-              this.velocityX *= 0.699999988079071D;
-              this.velocityZ *= 0.699999988079071D;
-           }
-
-        }
-
         this.velocityY += 0.125;
 
         Vec3d center = getPos();

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

@@ -39,7 +39,10 @@ public class GroundPoundParticle extends Particle {
     @Override
     public void tick() {
         super.tick();
+        spawnChildParticles();
+    }
 
+    protected void spawnChildParticles() {
         Vec3d vel = new Vec3d(0, (0.5 + (Math.sin(age) * 2.5)) * 5, 0);
 
         new Sphere(true, age, 1, 0, 1).offset(getPos()).randomPoints(random).forEach(point -> {

src/main/java/com/minelittlepony/unicopia/entity/FloatingArtefactEntity.java

@@ -23,11 +23,21 @@ public class FloatingArtefactEntity extends Entity {
 
     private static final TrackedData<ItemStack> ITEM = DataTracker.registerData(FloatingArtefactEntity.class, TrackedDataHandlerRegistry.ITEM_STACK);
     private static final TrackedData<Byte> STATE = DataTracker.registerData(FloatingArtefactEntity.class, TrackedDataHandlerRegistry.BYTE);
+    private static final TrackedData<Float> SPIN = DataTracker.registerData(FloatingArtefactEntity.class, TrackedDataHandlerRegistry.FLOAT);
+
+    private float bobAmount;
+    private float spinAmount;
 
-    private int age;
     private float health = 1;
     public final float positionSeed;
 
+    private int spinupDuration;
+
+    private float sourceSpin = 1;
+    private float targetSpin = 1;
+    private float spinChange;
+    private float spinChangeProgress;
+
     public FloatingArtefactEntity(EntityType<?> entityType, World world) {
         super(entityType, world);
 
@@ -38,6 +48,7 @@ public class FloatingArtefactEntity extends Entity {
     protected void initDataTracker() {
         dataTracker.startTracking(ITEM, ItemStack.EMPTY);
         dataTracker.startTracking(STATE, (byte)0);
+        dataTracker.startTracking(SPIN, 1F);
     }
 
     public ItemStack getStack() {
@@ -56,12 +67,21 @@ public class FloatingArtefactEntity extends Entity {
         dataTracker.set(STATE, (byte)state.ordinal());
     }
 
-    public void addSpin(int spin) {
+    public void addSpin(float spin, int duration) {
-        if (age != -32768) {
+        if (spin >= getSpin()) {
-            age += spin;
+            setSpin(spin);
+            spinupDuration = duration;
         }
     }
 
+    public void setSpin(float spin) {
+        dataTracker.set(SPIN, spin);
+    }
+
+    public float getSpin() {
+        return dataTracker.get(SPIN);
+    }
+
     @Override
     public void tick() {
         Vec3d pos = Vec3d.ofBottomCenter(getBlockPos());
@@ -76,6 +96,33 @@ public class FloatingArtefactEntity extends Entity {
             setStack(UItems.EMPTY_JAR.getDefaultStack());
         }
 
+        if (world.isClient) {
+            float spin = getSpin();
+            if (Math.abs(spin - targetSpin) > 1.0E-5F) {
+                spinChange = spin - targetSpin;
+                targetSpin = spin;
+                spinChangeProgress = 0;
+            }
+
+            if (spinChange != 0) {
+                if (spinChangeProgress < 1) {
+                    spinChangeProgress += 0.05F;
+                } else {
+                    sourceSpin = targetSpin;
+                    spinChange = 0;
+                    spinChangeProgress = 0;
+                }
+            }
+
+            spinAmount += sourceSpin + (spinChange * spinChangeProgress);
+            bobAmount++;
+        } else {
+            spinupDuration = Math.max(0, spinupDuration - 1);
+            if (spinupDuration <= 0) {
+                setSpin(1);
+            }
+        }
+
         if (stack.getItem() instanceof Artifact) {
             ((Artifact)stack.getItem()).onArtifactTick(this);
         }
@@ -84,16 +131,14 @@ public class FloatingArtefactEntity extends Entity {
             State state = getState();
             playSound(SoundEvents.BLOCK_BEACON_AMBIENT, state.getVolume(), state.getPitch());
         }
-
-        addSpin(1);
     }
 
     public float getVerticalOffset(float tickDelta) {
-        return MathHelper.sin((age + tickDelta) / 10F + positionSeed) * 0.025F + 0.05F;
+        return MathHelper.sin((bobAmount + tickDelta) / 10F + positionSeed) * 0.025F + 0.05F;
     }
 
     public float getRotation(float tickDelta) {
-        return (age + tickDelta) / 20 + positionSeed;
+        return (spinAmount + tickDelta) / 20 + positionSeed;
     }
 
     @Override

src/main/java/com/minelittlepony/unicopia/item/CrystalHeartItem.java

@@ -88,7 +88,7 @@ public class CrystalHeartItem extends Item implements FloatingArtefactEntity.Art
                 entity.setState(State.INITIALISING);
             }
 
-            entity.addSpin(2);
+            entity.addSpin(2, 10);
 
             BlockPos pos = entity.getBlockPos();
             entity.world.addParticle(ParticleTypes.COMPOSTER,
@@ -144,7 +144,8 @@ public class CrystalHeartItem extends Item implements FloatingArtefactEntity.Art
                     ParticleUtils.spawnParticles(new FollowingParticleEffect(UParticles.HEALTH_DRAIN, output, 0.2F), entity, 1);
                     output.heal(gives);
                 });
-                entity.addSpin((int)gives);
+
+                entity.addSpin(gives > 0 ? 20 : 10, 30);
             }
         }