From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: BillyGalbreath Date: Tue, 8 Dec 2020 20:24:52 -0600 Subject: [PATCH] MC-4: Fix item position desync This fixes item position desync (MC-4) by running the item coordinates through the encode/decode methods of the packet that causes the precision loss, which forces the server to lose the same precision as the client keeping them in sync. diff --git a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java index 3768a71491ef7836b9739bdaec7a077c523dbacd..a57957ace1a72b3308487f180a366c3879eceb21 100644 --- a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java +++ b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java @@ -8,11 +8,11 @@ public class VecDeltaCodec { public Vec3 base = Vec3.ZERO; // Paper private static long encode(double value) { - return Mth.lfloor(value * 4096.0D); + return Mth.lfloor(value * 4096.0D); // Paper - check ItemEntity#setPosRaw on update } private static double decode(long value) { - return (double)value / 4096.0D; + return (double)value / 4096.0D; // Paper - check ItemEntity#setPosRaw on update } public Vec3 decode(long x, long y, long z) { diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java index 508eb07ac137ca81e4f9015fe2665d992bd1cb72..83701f22e7903d0c4b9bea111dbed5d096a2ddf9 100644 --- a/src/main/java/net/minecraft/world/entity/Entity.java +++ b/src/main/java/net/minecraft/world/entity/Entity.java @@ -3970,6 +3970,16 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource { return; } // Paper end - rewrite chunk system + // Paper start - fix MC-4 + if (this instanceof ItemEntity) { + if (io.papermc.paper.configuration.GlobalConfiguration.get().misc.fixEntityPositionDesync) { + // encode/decode from ClientboundMoveEntityPacket + x = Mth.lfloor(x * 4096.0D) * (1 / 4096.0D); + y = Mth.lfloor(y * 4096.0D) * (1 / 4096.0D); + z = Mth.lfloor(z * 4096.0D) * (1 / 4096.0D); + } + } + // Paper end - fix MC-4 if (this.position.x != x || this.position.y != y || this.position.z != z) { this.position = new Vec3(x, y, z); int i = Mth.floor(x);