Optimize explosion entity raycasts

common/src/main/java/net/caffeinemc/mods/lithium/common/world/explosions/MutableExplosionClipContext.java

@@ -0,0 +1,15 @@
+package net.caffeinemc.mods.lithium.common.world.explosions;
+
+import net.minecraft.world.level.Level;
+import net.minecraft.world.phys.Vec3;
+
+public class MutableExplosionClipContext {
+    public final Level level;
+    public final Vec3 to;
+    public Vec3 from = null;
+
+    public MutableExplosionClipContext(Level level, Vec3 to) {
+        this.level = level;
+        this.to = to;
+    }
+}

common/src/main/java/net/caffeinemc/mods/lithium/mixin/world/explosions/block_raycast/ServerExplosionMixin.java

@@ -25,10 +25,7 @@
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.Unique;
-import org.spongepowered.asm.mixin.injection.At;
-import org.spongepowered.asm.mixin.injection.Constant;
-import org.spongepowered.asm.mixin.injection.Inject;
-import org.spongepowered.asm.mixin.injection.ModifyConstant;
+import org.spongepowered.asm.mixin.injection.*;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
@@ -46,6 +43,7 @@
 @Mixin(ServerExplosion.class)
 public abstract class ServerExplosionMixin {
 
+    @Unique
     private static final HashSet<?> DUMMY_HASHSET = new HashSet<>(0);
     @Shadow
     @Final
@@ -103,13 +101,14 @@ private void init(ServerLevel serverLevel, Entity entity, DamageSource damageSou
         this.explodeAirBlocks = explodeAir;
     }
 
-//    @Redirect(
-//            method = "calculateExplodedPositions",
-//            at = @At(value = "NEW", target = "()Ljava/util/HashSet;", remap = false)
-//    )
-//    public HashSet<BlockPos> skipNewHashSet() {
-//        return null; //TODO this crashes
-//    }
+    @SuppressWarnings("unchecked")
+    @Redirect(
+            method = "calculateExplodedPositions",
+            at = @At(value = "NEW", target = "()Ljava/util/HashSet;", remap = false)
+    )
+    public HashSet<BlockPos> skipNewHashSet() {
+        return (HashSet<BlockPos>) DUMMY_HASHSET;
+    }
 
     @ModifyConstant(
             method = "calculateExplodedPositions",

common/src/main/java/net/caffeinemc/mods/lithium/mixin/world/explosions/entity_raycast/ServerExplosionMixin.java

@@ -0,0 +1,131 @@
+package net.caffeinemc.mods.lithium.mixin.world.explosions.entity_raycast;
+
+import com.llamalad7.mixinextras.sugar.Share;
+import com.llamalad7.mixinextras.sugar.ref.LocalRef;
+import net.caffeinemc.mods.lithium.common.util.Pos;
+import net.caffeinemc.mods.lithium.common.world.explosions.MutableExplosionClipContext;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.*;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.phys.BlockHitResult;
+import net.minecraft.world.phys.Vec3;
+import net.minecraft.world.phys.shapes.CollisionContext;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import java.util.function.BiFunction;
+
+/**
+ * @author Crosby
+ */
+@Mixin(ServerExplosion.class)
+public class ServerExplosionMixin {
+    @SuppressWarnings("DataFlowIssue")
+    @Unique
+    private static final BlockHitResult MISS = BlockHitResult.miss(null, null, null);
+    @SuppressWarnings("DataFlowIssue")
+    @Unique
+    private static final ClipContext EMPTY = new ClipContext(null, null, null, null, (CollisionContext) null);
+
+    /**
+     * Pre-allocate our {@link MutableExplosionClipContext}.
+     * @author Crosby
+     */
+    @Inject(
+            method = "getSeenPercent",
+            at = @At("HEAD")
+    )
+    private static void createMutableContext(Vec3 to, Entity entity, CallbackInfoReturnable<Float> cir, @Share("context") LocalRef<MutableExplosionClipContext> contextRef, @Share("blockHitFactory") LocalRef<BiFunction<MutableExplosionClipContext, BlockPos, BlockHitResult>> hitFactoryRef) {
+        contextRef.set(new MutableExplosionClipContext(entity.level(), to));
+        hitFactoryRef.set(blockHitFactory());
+    }
+
+    /**
+     * Remove {@link ClipContext} allocation.
+     * @author Crosby
+     */
+    @Redirect(
+            method = "getSeenPercent",
+            at = @At(value = "NEW", target = "net/minecraft/world/level/ClipContext")
+    )
+    private static ClipContext removeUnusedObject(Vec3 from, Vec3 to, ClipContext.Block p_45690_, ClipContext.Fluid p_45691_, Entity entity, @Share("context") LocalRef<MutableExplosionClipContext> contextRef) {
+        contextRef.get().from = from;
+        return EMPTY;
+    }
+
+    /**
+     * Use specialized hit factory and remove miss allocation.
+     * @author Crosby
+     */
+    @Redirect(
+            method = "getSeenPercent",
+            at = @At(value = "INVOKE", target = "Lnet/minecraft/world/level/Level;clip(Lnet/minecraft/world/level/ClipContext;)Lnet/minecraft/world/phys/BlockHitResult;")
+    )
+    private static BlockHitResult simplifyRaycast(Level level, ClipContext nullContext, @Share("context") LocalRef<MutableExplosionClipContext> contextRef, @Share("blockHitFactory") LocalRef<BiFunction<MutableExplosionClipContext, BlockPos, BlockHitResult>> hitFactoryRef) {
+        MutableExplosionClipContext context = contextRef.get();
+        BiFunction<MutableExplosionClipContext, BlockPos, BlockHitResult> blockHitFactory = hitFactoryRef.get();
+        return BlockGetter.traverseBlocks(context.from, context.to, context, blockHitFactory, ctx -> MISS);
+    }
+
+    /**
+     * Specialized version of {@link net.caffeinemc.mods.lithium.mixin.world.raycast.BlockGetterMixin#blockHitFactory(ClipContext)}
+     * where the inlined shape getter allows us to replace the {@link ClipContext} with our own {@link MutableExplosionClipContext},
+     * eliminating extra allocations from the loop body of {@link ServerExplosion#getSeenPercent(Vec3, Entity)}.
+     * We also remove fluid handling and hit direction computation.
+     * @author Crosby
+     */
+    @Unique
+    private static BiFunction<MutableExplosionClipContext, BlockPos, BlockHitResult> blockHitFactory() {
+        return new BiFunction<>() {
+            int chunkX = Integer.MIN_VALUE, chunkZ = Integer.MIN_VALUE;
+            ChunkAccess chunk = null;
+
+            @Override
+            public BlockHitResult apply(MutableExplosionClipContext context, BlockPos blockPos) {
+                BlockState state = getBlock(context.level, blockPos);
+
+                return state.getCollisionShape(context.level, blockPos).clip(context.from, context.to, blockPos);
+            }
+
+            private BlockState getBlock(LevelReader world, BlockPos blockPos) {
+                if (world.isOutsideBuildHeight(blockPos.getY())) {
+                    return Blocks.VOID_AIR.defaultBlockState();
+                }
+                int chunkX = Pos.ChunkCoord.fromBlockCoord(blockPos.getX());
+                int chunkZ = Pos.ChunkCoord.fromBlockCoord(blockPos.getZ());
+
+                // Avoid calling into the chunk manager as much as possible through managing chunks locally
+                if (this.chunkX != chunkX || this.chunkZ != chunkZ) {
+                    this.chunk = world.getChunk(chunkX, chunkZ);
+
+                    this.chunkX = chunkX;
+                    this.chunkZ = chunkZ;
+                }
+
+                final ChunkAccess chunk = this.chunk;
+
+                // If the chunk is missing or out of bounds, assume that it is air
+                if (chunk != null) {
+                    // We operate directly on chunk sections to avoid interacting with BlockPos and to squeeze out as much
+                    // performance as possible here
+                    LevelChunkSection section = chunk.getSections()[Pos.SectionYIndex.fromBlockCoord(chunk, blockPos.getY())];
+
+                    // If the section doesn't exist or is empty, assume that the block is air
+                    if (section != null && !section.hasOnlyAir()) {
+                        return section.getBlockState(blockPos.getX() & 15, blockPos.getY() & 15, blockPos.getZ() & 15);
+                    }
+                }
+
+                return Blocks.AIR.defaultBlockState();
+            }
+        };
+    }
+}

common/src/main/java/net/caffeinemc/mods/lithium/mixin/world/explosions/entity_raycast/package-info.java

@@ -0,0 +1,4 @@
+@MixinConfigOption(description = "Various improvements to explosion entity damage, e.g. simplifying the raycasts.")
+package net.caffeinemc.mods.lithium.mixin.world.explosions.entity_raycast;
+
+import net.caffeinemc.gradle.MixinConfigOption;

common/src/main/java/net/caffeinemc/mods/lithium/mixin/world/raycast/BlockGetterMixin.java

@@ -77,6 +77,9 @@ public BlockHitResult apply(ClipContext innerContext, BlockPos pos) {
                 return d <= e ? blockHitResult : fluidHitResult;
             }
 
+            /**
+             * Modifications to this method should also be done in {@link net.caffeinemc.mods.lithium.mixin.world.explosions.entity_raycast.ServerExplosionMixin#blockHitFactory()}
+             */
             private BlockState getBlock(LevelReader world, BlockPos blockPos) {
                 if (world.isOutsideBuildHeight(blockPos.getY())) {
                     return Blocks.VOID_AIR.defaultBlockState();

common/src/main/resources/lithium.mixins.json

@@ -232,6 +232,7 @@
     "world.combined_heightmap_update.HeightmapAccessor",
     "world.combined_heightmap_update.LevelChunkMixin",
     "world.explosions.block_raycast.ServerExplosionMixin",
+    "world.explosions.entity_raycast.ServerExplosionMixin",
     "world.game_events.dispatch.GameEventDispatcherMixin",
     "world.game_events.dispatch.LevelChunkMixin",
     "world.inline_block_access.LevelChunkMixin",

lithium-fabric-mixin-config.md

@@ -632,6 +632,10 @@ Various improvements to explosions.
 (default: `true`)  
 Various improvements to explosion block damage, e.g. not accessing blocks along an explosion ray multiple times
 
+### `mixin.world.explosions.entity_raycast`
+(default: `true`)  
+Various improvements to explosion entity damage, e.g. simplifying the raycasts.
+
 ### `mixin.world.game_events`
 (default: `true`)  
 Various improvements to game events (vibrations) that are detected by allays, wardens and several sculk blocks.

lithium-neoforge-mixin-config.md

@@ -609,6 +609,10 @@ Various improvements to explosions.
 (default: `true`)  
 Various improvements to explosion block damage, e.g. not accessing blocks along an explosion ray multiple times
 
+### `mixin.world.explosions.entity_raycast`
+(default: `true`)  
+Various improvements to explosion entity damage, e.g. simplifying the raycasts.
+
 ### `mixin.world.game_events`
 (default: `true`)  
 Various improvements to game events (vibrations) that are detected by allays, wardens and several sculk blocks.