From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Byteflux <byte@byteflux.net>
Date: Wed, 2 Mar 2016 11:59:48 -0600
Subject: [PATCH] Optimize explosions

The process of determining an entity's exposure from explosions can be
expensive when there are hundreds or more entities in range.

This patch adds a per-tick cache that is used for storing and retrieving
an entity's exposure during an explosion.

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index f70468b2cc4a782d3d7cc7854192fbbc3ad3020f..9c26725e12adb2d17b9fa27f632fbad02e904c9a 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1611,6 +1611,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             gameprofilerfiller.pop();
             gameprofilerfiller.pop();
+            worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
         }
 
         gameprofilerfiller.popPush("connection");
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 3d2f579cf2b7b96f4ce2588f9655d2287767b01c..7e6680d0618173e23d323b4b29f0a2fc966789e7 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -169,6 +169,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     private org.spigotmc.TickLimiter entityLimiter;
     private org.spigotmc.TickLimiter tileLimiter;
     private int tileTickPosition;
+    public final Map<ServerExplosion.CacheKey, Float> explosionDensityCache = new HashMap<>(); // Paper - Optimize explosions
 
     public CraftWorld getWorld() {
         return this.world;
diff --git a/src/main/java/net/minecraft/world/level/ServerExplosion.java b/src/main/java/net/minecraft/world/level/ServerExplosion.java
index 67685dfa8eb4a74e70ef982291a55d145d6abc66..bbe50f60e653e60c844ca6688e781fa69d67905a 100644
--- a/src/main/java/net/minecraft/world/level/ServerExplosion.java
+++ b/src/main/java/net/minecraft/world/level/ServerExplosion.java
@@ -206,7 +206,7 @@ public class ServerExplosion implements Explosion {
                         d3 /= d4;
                         boolean flag = this.damageCalculator.shouldDamageEntity(this, entity);
                         float f1 = this.damageCalculator.getKnockbackMultiplier(entity);
-                        float f2 = !flag && f1 == 0.0F ? 0.0F : ServerExplosion.getSeenPercent(this.center, entity);
+                        float f2 = !flag && f1 == 0.0F ? 0.0F : this.getBlockDensity(this.center, entity); // Paper - Optimize explosions
 
                         if (flag) {
                             // CraftBukkit start
@@ -487,4 +487,85 @@ public class ServerExplosion implements Explosion {
 
         }
     }
+
+    // Paper start - Optimize explosions
+    private float getBlockDensity(Vec3 vec3d, Entity entity) {
+        if (!this.level.paperConfig().environment.optimizeExplosions) {
+            return getSeenPercent(vec3d, entity);
+        }
+        CacheKey key = new CacheKey(this, entity.getBoundingBox());
+        Float blockDensity = this.level.explosionDensityCache.get(key);
+        if (blockDensity == null) {
+            blockDensity = getSeenPercent(vec3d, entity);
+            this.level.explosionDensityCache.put(key, blockDensity);
+        }
+
+        return blockDensity;
+    }
+
+    static class CacheKey {
+        private final Level world;
+        private final double posX, posY, posZ;
+        private final double minX, minY, minZ;
+        private final double maxX, maxY, maxZ;
+
+        public CacheKey(Explosion explosion, AABB aabb) {
+            this.world = explosion.level();
+            this.posX = explosion.center().x;
+            this.posY = explosion.center().y;
+            this.posZ = explosion.center().z;
+            this.minX = aabb.minX;
+            this.minY = aabb.minY;
+            this.minZ = aabb.minZ;
+            this.maxX = aabb.maxX;
+            this.maxY = aabb.maxY;
+            this.maxZ = aabb.maxZ;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+
+            CacheKey cacheKey = (CacheKey) o;
+
+            if (Double.compare(cacheKey.posX, posX) != 0) return false;
+            if (Double.compare(cacheKey.posY, posY) != 0) return false;
+            if (Double.compare(cacheKey.posZ, posZ) != 0) return false;
+            if (Double.compare(cacheKey.minX, minX) != 0) return false;
+            if (Double.compare(cacheKey.minY, minY) != 0) return false;
+            if (Double.compare(cacheKey.minZ, minZ) != 0) return false;
+            if (Double.compare(cacheKey.maxX, maxX) != 0) return false;
+            if (Double.compare(cacheKey.maxY, maxY) != 0) return false;
+            if (Double.compare(cacheKey.maxZ, maxZ) != 0) return false;
+            return world.equals(cacheKey.world);
+        }
+
+        @Override
+        public int hashCode() {
+            int result;
+            long temp;
+            result = world.hashCode();
+            temp = Double.doubleToLongBits(posX);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(posY);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(posZ);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(minX);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(minY);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(minZ);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(maxX);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(maxY);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            temp = Double.doubleToLongBits(maxZ);
+            result = 31 * result + (int) (temp ^ (temp >>> 32));
+            return result;
+        }
+    }
+    // Paper end
 }