Paper/Spigot-Server-Patches/0362-MC-2025-Save-and-load-entity-AABB-to-prevent-wobble.patch
Aikar 6d41af029c
Updated Upstream (Bukkit/CraftBukkit/Spigot)
Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Bukkit Changes:
3e2858f6 SPIGOT-4352: MoistureChangeEvent
5466e281 Add BlockDispenseArmorEvent

CraftBukkit Changes:
3123a069 SPIGOT-4352: MoistureChangeEvent
226db0ea Add BlockDispenseArmorEvent
cd367fa4 Fix bad thread safety in ChunkRegionLoader
3f5ca5f2 SPIGOT-4355: Improve cancelling VehicleEnterEvent

Spigot Changes:
145a37ae Rebuild patches
3f2423cc Rebuild patches
2018-09-09 15:26:56 -04:00

93 lines
5.4 KiB
Diff

From a9658dc0a2bb54d4863a966a813a70d39fc2896f Mon Sep 17 00:00:00 2001
From: Zach Brown <zach.brown@destroystokyo.com>
Date: Tue, 4 Sep 2018 19:07:57 -0400
Subject: [PATCH] MC-2025: Save and load entity AABB to prevent wobble
What follows is a summarized analysis provided on the Mojira and associated subreddit by various MC community members
who have investigated this issue and found a solution. This work is largely a result of their efforts.
The underlying cause of MC-2025 is that sometimes an AABB ends up slightly smaller than the desired width. If this
happens before the entity is pushed up against a boundary (i.e. blocks or walls), then upon chunk save and reload, the
AABB size will be recomputed such that it is intersecting the wall, allowing the entity to be pushed into the wall,
suffocate, and die. Although the rounding artifacts get larger at larger world coordinates, the drift we see is
miniscule. Closer to the world origin, we have seen error on the order of 2-46. Compare this to the fact that
(due to MC-4), entity coordinates send to clients are quantized to multiples of 1/4096 (2-12).
But, OMG, do the rounding errors mean that AABB's accumulate shrinkage over time? Actually, no. The statistics on IEEE
rounding do not have that kind of bias. What has not been stated is that the AABB is just as likely to end up larger
than the expected width; on save and reload, the entity ends up slightly away from the wall, and we don't notice any
problem. In reality, the AABB size ends up undergoing random wobble around the expected value all the time, and that
wobble isn't functionally any different from the kind we'd get even if we tried to force the AABB size to be stable!
This reasoning leads us to one clear conclusion: The simplest, least invasive, and most correct solution is to just
store the AABB in NBT data on chunk save and restore the AABB exactly as it was saved upon reload.
diff --git a/src/main/java/net/minecraft/server/AxisAlignedBB.java b/src/main/java/net/minecraft/server/AxisAlignedBB.java
index 92edfe0295..624f0e3956 100644
--- a/src/main/java/net/minecraft/server/AxisAlignedBB.java
+++ b/src/main/java/net/minecraft/server/AxisAlignedBB.java
@@ -3,12 +3,12 @@ package net.minecraft.server;
import javax.annotation.Nullable;
public class AxisAlignedBB {
- public final double a;
- public final double b;
- public final double c;
- public final double d;
- public final double e;
- public final double f;
+ public final double a; public double getMinX() { return this.a; } // Paper - OBFHELPER
+ public final double b; public double getMinY() { return this.b; } // Paper - OBFHELPER
+ public final double c; public double getMinZ() { return this.c; } // Paper - OBFHELPER
+ public final double d; public double getMaxX() { return this.d; } // Paper - OBFHELPER
+ public final double e; public double getMaxY() { return this.e; } // Paper - OBFHELPER
+ public final double f; public double getMaxZ() { return this.f; } // Paper - OBFHELPER
public AxisAlignedBB(double d0, double d1, double d2, double d3, double d4, double d5) {
this.a = Math.min(d0, d3);
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index f609e2ceda..bcd7af059e 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -1658,6 +1658,12 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
if (spawnedViaMobSpawner) {
nbttagcompound.setBoolean("Paper.FromMobSpawner", true);
}
+ // Paper start - MC-2025 fix - Save entity AABB and load it, floating point issues recalculating AABB can result in wobble
+ AxisAlignedBB boundingBox = this.getBoundingBox();
+ nbttagcompound.set("Paper.AAAB", this.createList(
+ boundingBox.getMinX(), boundingBox.getMinY(), boundingBox.getMinZ(),
+ boundingBox.getMaxX(), boundingBox.getMaxY(), boundingBox.getMaxZ()
+ ));
// Paper end
return nbttagcompound;
} catch (Throwable throwable) {
@@ -1747,6 +1753,16 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
if (this.aD()) {
this.setPosition(this.locX, this.locY, this.locZ);
}
+ // Paper start - MC-2025 fix - Save entity AABB and load it, floating point issues recalculating AABB can result in wobble
+ // Placement is important, always after the setPosition call above
+ if (nbttagcompound.hasKey("Paper.AABB")) {
+ NBTTagList savedBB = nbttagcompound.getList("Paper.AABB", 6);
+ this.setBoundingBox(new AxisAlignedBB(
+ savedBB.getDoubleAt(0), savedBB.getDoubleAt(1), savedBB.getDoubleAt(2),
+ savedBB.getDoubleAt(3), savedBB.getDoubleAt(4), savedBB.getDoubleAt(5)
+ ));
+ }
+ // Paper end
// CraftBukkit start
if (this instanceof EntityLiving) {
@@ -2816,6 +2832,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
return this.boundingBox;
}
+ public void setBoundingBox(AxisAlignedBB axisAlignedBB) { this.a(axisAlignedBB); } // Paper - OBFHELPER
public void a(AxisAlignedBB axisalignedbb) {
// CraftBukkit start - block invalid bounding boxes
double a = axisalignedbb.a,
--
2.18.0