mirror of
https://github.com/PaperMC/Paper.git
synced 2024-11-23 02:55:47 +01:00
fb9e60b238
This work is largely a result of the analysis done on the Mojang issue tracker. See patch header for additional information.
93 lines
5.4 KiB
Diff
93 lines
5.4 KiB
Diff
From cf0b7a7bedd11fa9cb57217baf8486647bbe65a2 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 92edfe029..624f0e395 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 2b1affd03..1fae9aa07 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) {
|
|
@@ -2815,6 +2831,7 @@ 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
|
|
|