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fix: handle LpVec3 movement encoding in SpawnEntity for 1.21.9+

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Minecraft 1.21.9 changed the SpawnEntity (Add Entity) packet layout:
the velocity/movement field was moved before the angle fields and
switched from 3 x Short to a new variable-length LpVec3 encoding.

Add ReadNextLpVec3() to consume the LpVec3 wire format (1 byte header,
optionally 5+ more bytes with a continuation VarInt), and update
ReadNextEntity() to use the new field order for protocol >= 773.

Made-with: Cursor
This commit is contained in:
BruceChen 2026-03-21 14:11:23 +08:00
parent 88e9c671da
commit 6d3c58b29f
1 changed files with 49 additions and 12 deletions
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61
MinecraftClient/Protocol/Handlers/DataTypes.cs
View file

@ -559,11 +559,32 @@ namespace MinecraftClient.Protocol.Handlers
int data = -1;
byte entityPitch, entityYaw;
if (living)
if (protocolversion >= Protocol18Handler.MC_1_21_9_Version)
{
// 1.21.9+: LpVec3 movement before angles, unified format
ReadNextLpVec3(cache); // Movement (LpVec3)
entityPitch = ReadNextByte(cache); // xRot
entityYaw = ReadNextByte(cache); // yRot
ReadNextByte(cache); // yHeadRot
data = ReadNextVarInt(cache); // Data
}
else if (living)
{
entityYaw = ReadNextByte(cache); // Yaw
entityPitch = ReadNextByte(cache); // Pitch
entityPitch = ReadNextByte(cache); // Head Pitch
// Velocity (3 shorts)
if (protocolversion < Protocol18Handler.MC_1_9_Version)
{
// no velocity for living entities in <1.9
}
else
{
ReadNextShort(cache);
ReadNextShort(cache);
ReadNextShort(cache);
}
}
else
{
@ -577,24 +598,24 @@ namespace MinecraftClient.Protocol.Handlers
data = protocolversion >= Protocol18Handler.MC_1_19_Version
? ReadNextVarInt(cache)
: ReadNextInt(cache);
}
// In 1.8 those 3 fields for Velocity are optional
if (protocolversion < Protocol18Handler.MC_1_9_Version)
{
if (data != 0)
// Velocity (3 shorts)
if (protocolversion < Protocol18Handler.MC_1_9_Version)
{
if (data != 0)
{
ReadNextShort(cache);
ReadNextShort(cache);
ReadNextShort(cache);
}
}
else
{
ReadNextShort(cache);
ReadNextShort(cache);
ReadNextShort(cache);
}
}
else
{
ReadNextShort(cache);
ReadNextShort(cache);
ReadNextShort(cache);
}
return new Entity(entityID, entityType, new Location(entityX, entityY, entityZ), entityYaw, entityPitch,
data);
@ -945,6 +966,22 @@ namespace MinecraftClient.Protocol.Handlers
}
}
/// <summary>
/// Read an LpVec3 (low-precision vec3) from the cache (1.21.9+).
/// Variable-length encoding: first byte 0 = zero vector; otherwise
/// 2 bytes + 4 bytes (6 total), plus an optional VarInt continuation.
/// </summary>
public void ReadNextLpVec3(Queue<byte> cache)
{
int first = ReadNextByte(cache);
if (first == 0)
return;
ReadNextByte(cache); // second byte
ReadData(4, cache); // uint32
if ((first & 4) == 4) // continuation bit set
ReadNextVarInt(cache);
}
/// <summary>
/// Consume bytes for a ResolvableProfile (1.21.9+).
/// Wire: Either(GameProfile, Partial) + PlayerSkin.Patch