Paper/patches/server/0286-Prevent-rayTrace-from-loading-chunks.patch
Spottedleaf 01a13871de
Rewrite chunk system (#8177)
Patch documentation to come

Issues with the old system that are fixed now:
- World generation does not scale with cpu cores effectively.
- Relies on the main thread for scheduling and maintaining chunk state, dropping chunk load/generate rates at lower tps.
- Unreliable prioritisation of chunk gen/load calls that block the main thread.
- Shutdown logic is utterly unreliable, as it has to wait for all chunks to unload - is it guaranteed that the chunk system is in a state on shutdown that it can reliably do this? Watchdog shutdown also typically failed due to thread checks, which is now resolved.
- Saving of data is not unified (i.e can save chunk data without saving entity data, poses problems for desync if shutdown is really abnormal.
- Entities are not loaded with chunks. This caused quite a bit of headache for Chunk#getEntities API, but now the new chunk system loads entities with chunks so that they are ready whenever the chunk loads in. Effectively brings the behavior back to 1.16 era, but still storing entities in their own separate regionfiles.

The above list is not complete. The patch documentation will complete it.

New chunk system hard relies on starlight and dataconverter, and most importantly the new concurrent utilities in ConcurrentUtil.

Some of the old async chunk i/o interface (i.e the old file io thread reroutes _some_ calls to the new file io thread) is kept for plugin compat reasons. It will be removed in the next major version of minecraft.

The old legacy chunk system patches have been moved to the removed folder in case we need them again.
2022-09-26 01:02:51 -07:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 26 Nov 2018 19:21:58 -0500
Subject: [PATCH] Prevent rayTrace from loading chunks
ray tracing into an unloaded chunk should be treated as a miss
this saves a ton of lag for when AI tries to raytrace near unloaded chunks.
diff --git a/src/main/java/net/minecraft/world/level/BlockGetter.java b/src/main/java/net/minecraft/world/level/BlockGetter.java
index 8a979600b49e8a11982577fb6dd79503e2521a0f..bca0838e40bc91d78e9b93df5318642d1c9f341e 100644
--- a/src/main/java/net/minecraft/world/level/BlockGetter.java
+++ b/src/main/java/net/minecraft/world/level/BlockGetter.java
@@ -75,7 +75,15 @@ public interface BlockGetter extends LevelHeightAccessor {
// CraftBukkit start - moved block handling into separate method for use by Block#rayTrace
default BlockHitResult clip(ClipContext raytrace1, BlockPos blockposition) {
- BlockState iblockdata = this.getBlockState(blockposition);
+ // Paper start - Prevent raytrace from loading chunks
+ BlockState iblockdata = this.getBlockStateIfLoaded(blockposition);
+ if (iblockdata == null) {
+ // copied the last function parameter (listed below)
+ Vec3 vec3d = raytrace1.getFrom().subtract(raytrace1.getTo());
+
+ return BlockHitResult.miss(raytrace1.getTo(), Direction.getNearest(vec3d.x, vec3d.y, vec3d.z), new BlockPos(raytrace1.getTo()));
+ }
+ // Paper end
FluidState fluid = this.getFluidState(blockposition);
Vec3 vec3d = raytrace1.getFrom();
Vec3 vec3d1 = raytrace1.getTo();