Fix #38: Cap pushing velocities to region size

Author: PureGero

shreddedpaper-server/minecraft-patches/sources/net/minecraft/world/entity/Entity.java.patch

@@ -84,6 +84,15 @@
              BlockPos blockPos = this.mainSupportingBlockPos.get();
              if (!(yOffset > 1.0E-5F)) {
                  return blockPos;
+@@ -2377,7 +_,7 @@
+                 }
+                 delta = event.getKnockback();
+             }
+-            this.setDeltaMovement(this.getDeltaMovement().add(delta.getX(), delta.getY(), delta.getZ()));
++            this.setDeltaMovement(this.getDeltaMovement().add(delta.getX(), delta.getY(), delta.getZ()).shreddedPaperCapToRegionSize()); // ShreddedPaper - cap pushing delta to region size
+             // Paper end - Add EntityKnockbackByEntityEvent and EntityPushedByEntityAttackEvent
+             this.needsSync = true;
+         }
 @@ -3546,7 +_,9 @@
          }
      }
@@ -127,14 +136,23 @@
              // Paper start - gateway-specific teleport event
              final org.bukkit.event.entity.EntityTeleportEvent teleEvent;
              if (this.portalProcess != null && this.portalProcess.isSamePortal(((net.minecraft.world.level.block.EndGatewayBlock) Blocks.END_GATEWAY)) && this.level.getBlockEntity(this.portalProcess.getEntryPosition()) instanceof net.minecraft.world.level.block.entity.TheEndGatewayBlockEntity theEndGatewayBlockEntity) {
+@@ -4920,7 +_,7 @@
+             pushVector = pushVector.normalize().scale(0.0045000000000000005);
+         }
+ 
+-        this.setDeltaMovement(currMovement.add(pushVector));
++        this.setDeltaMovement(currMovement.add(pushVector).shreddedPaperCapToRegionSize()); // ShreddedPaper - cap pushing delta to region size
+ 
+         // note: inFluid = true here as pushVector != 0
+         return true;
 @@ -4996,6 +_,12 @@
 
      public void setDeltaMovement(Vec3 deltaMovement) {
          if (deltaMovement.isFinite()) {
 +            // ShreddedPaper start - why is something setting the entity velocity to larger than one region...
 +            if (deltaMovement.horizontalDistanceSqr() > RegionPos.MAX_DISTANCE_SQR + 1 && deltaMovement.horizontalDistanceSqr() > this.deltaMovement.horizontalDistanceSqr()) {
 +                LOGGER.warn("Velocity is being set larger than the ShreddedPaper region size: {} for entity {}", deltaMovement, this, new Exception("Velocity larger than region size, limiting velocity to region size"));
-+                deltaMovement = deltaMovement.normalize().scale(RegionPos.MAX_DISTANCE_SQR);
++                deltaMovement = deltaMovement.shreddedPaperCapToRegionSize();
 +            }
 +            // ShreddedPaper end - why is something setting the entity velocity to larger than one region...
              synchronized (this.posLock) { // Paper - detailed watchdog information

shreddedpaper-server/minecraft-patches/sources/net/minecraft/world/phys/Vec3.java.patch

@@ -1,10 +1,29 @@
 --- a/net/minecraft/world/phys/Vec3.java
 +++ b/net/minecraft/world/phys/Vec3.java
-@@ -4,6 +_,7 @@
+@@ -1,9 +_,11 @@
+ package net.minecraft.world.phys;
+ 
+ import com.mojang.serialization.Codec;
++import io.multipaper.shreddedpaper.region.RegionPos;
  import io.netty.buffer.ByteBuf;
  import java.util.EnumSet;
  import java.util.List;
 +
  import net.minecraft.core.Direction;
  import net.minecraft.core.Position;
  import net.minecraft.core.Vec3i;
+@@ -335,4 +_,14 @@
+     public boolean isFinite() {
+         return Double.isFinite(this.x) && Double.isFinite(this.y) && Double.isFinite(this.z);
+     }
++
++    // ShreddedPaper start - cap velocity to region size
++    public Vec3 shreddedPaperCapToRegionSize() {
++        double horizontalDistanceSqr = this.horizontalDistanceSqr();
++        if (horizontalDistanceSqr > RegionPos.MAX_DISTANCE_SQR) {
++            return this.scale((RegionPos.MAX_DISTANCE - 1) / Math.sqrt(horizontalDistanceSqr)); // Subtract 1 to ensure no double precision issues causes horizontalDistance > RegionPos.MAX_DISTANCE
++        }
++        return this;
++    }
++    // ShreddedPaper end - cap velocity to region size
+ }

shreddedpaper-server/src/main/java/io/multipaper/shreddedpaper/region/RegionPos.java

@@ -1,6 +1,7 @@
 package io.multipaper.shreddedpaper.region;
 
 import com.mojang.logging.LogUtils;
+import io.netty.util.internal.MathUtil;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.SectionPos;
 import net.minecraft.world.level.ChunkPos;
@@ -16,7 +17,8 @@ public class RegionPos {
     public static final int REGION_SIZE; // eg 8 (for an 8x8 region)
     public static final int REGION_SHIFT; // eg 3 (1 << 3 == 8)
     public static final int REGION_SIZE_MASK; // eg 7 (9 % 8 == 9 & 7 == 1)
-    public static final int MAX_DISTANCE_SQR;
+    public static final double MAX_DISTANCE_SQR;
+    public static final double MAX_DISTANCE;
 
     static {
         // desiredRegionSize = 7 -> shift = 3, size = 8, mask = 7
@@ -45,7 +47,8 @@ public class RegionPos {
 
         LOGGER.info("Using region size: {}, shift={}, mask={}", REGION_SIZE, REGION_SHIFT, REGION_SIZE_MASK);
 
-        MAX_DISTANCE_SQR = RegionPos.REGION_SIZE * 16 * RegionPos.REGION_SIZE * 16;
+        MAX_DISTANCE_SQR = (double) RegionPos.REGION_SIZE * 16 * RegionPos.REGION_SIZE * 16;
+        MAX_DISTANCE = Math.sqrt(MAX_DISTANCE_SQR);
     }
 
     public final int x;