doc/lua_api.md

@@ -7465,15 +7465,20 @@ child will follow movement and rotation of that bone.
     * Sets the position of the object.
     * No-op if object is attached.
     * `pos` is a vector `{x=num, y=num, z=num}`
+* `add_pos(pos)`:
+    * Changes position by adding to the current position.
+    * No-op if object is attached.
+    * `pos` is a vector `{x=num, y=num, z=num}`.
+    * In comparison to using `set_pos`, `add_pos` will avoid synchronization problems.
 * `get_velocity()`: returns the velocity, a vector.
 * `add_velocity(vel)`
     * Changes velocity by adding to the current velocity.
     * `vel` is a vector, e.g. `{x=0.0, y=2.3, z=1.0}`
-    * In comparison to using get_velocity, adding the velocity and then using
+    * In comparison to using `get_velocity`, adding the velocity and then using
-      set_velocity, add_velocity is supposed to avoid synchronization problems.
+      `set_velocity`, `add_velocity` is supposed to avoid synchronization problems.
-      Additionally, players also do not support set_velocity.
+      Additionally, players also do not support `set_velocity`.
     * If object is a player:
-        * Does not apply during free_move.
+        * Does not apply during `free_move`.
         * Note that since the player speed is normalized at each move step,
           increasing e.g. Y velocity beyond what would usually be achieved
           (see: physics overrides) will cause existing X/Z velocity to be reduced.

games/devtest/mods/unittests/player.lua

@@ -68,3 +68,19 @@ local function run_player_meta_tests(player)
 	assert(meta:equals(meta2))
 end
 unittests.register("test_player_meta", run_player_meta_tests, {player=true})
+
+--
+-- Player add pos
+--
+local function run_player_add_pos_tests(player)
+	local pos = player:get_pos()
+	player:add_pos(vector.new(0, 1000, 0))
+	local newpos = player:get_pos()
+	player:add_pos(vector.new(0, -1000, 0))
+	local backpos = player:get_pos()
+	local newdist = vector.distance(pos, newpos)
+	assert(math.abs(newdist - 1000) <= 1)
+	assert(vector.distance(pos, backpos) <= 1)
+end
+unittests.register("test_player_add_pos", run_player_add_pos_tests, {player=true})
+

src/client/client.h

@@ -196,6 +196,7 @@ public:
 	void handleCommand_HP(NetworkPacket* pkt);
 	void handleCommand_Breath(NetworkPacket* pkt);
 	void handleCommand_MovePlayer(NetworkPacket* pkt);
+	void handleCommand_MovePlayerRel(NetworkPacket* pkt);
 	void handleCommand_DeathScreen(NetworkPacket* pkt);
 	void handleCommand_AnnounceMedia(NetworkPacket* pkt);
 	void handleCommand_Media(NetworkPacket* pkt);

src/client/localplayer.h

@@ -129,6 +129,11 @@ public:
 		m_position = position;
 		m_sneak_node_exists = false;
 	}
+	inline void addPosition(const v3f &added_pos)
+	{
+		m_position += added_pos;
+		m_sneak_node_exists = false;
+	}
 
 	v3f getPosition() const { return m_position; }
 

src/network/clientopcodes.cpp

@@ -117,7 +117,7 @@ const ToClientCommandHandler toClientCommandTable[TOCLIENT_NUM_MSG_TYPES] =
 	{ "TOCLIENT_SET_SUN",                  TOCLIENT_STATE_CONNECTED, &Client::handleCommand_HudSetSun }, // 0x5a
 	{ "TOCLIENT_SET_MOON",                 TOCLIENT_STATE_CONNECTED, &Client::handleCommand_HudSetMoon }, // 0x5b
 	{ "TOCLIENT_SET_STARS",                TOCLIENT_STATE_CONNECTED, &Client::handleCommand_HudSetStars }, // 0x5c
-	null_command_handler,
+	{ "TOCLIENT_MOVE_PLAYER_REL",          TOCLIENT_STATE_CONNECTED, &Client::handleCommand_MovePlayerRel }, // 0x5d,
 	null_command_handler,
 	null_command_handler,
 	{ "TOCLIENT_SRP_BYTES_S_B",            TOCLIENT_STATE_NOT_CONNECTED, &Client::handleCommand_SrpBytesSandB }, // 0x60

src/network/clientpackethandler.cpp

@@ -635,6 +635,17 @@ void Client::handleCommand_MovePlayer(NetworkPacket* pkt)
 	m_client_event_queue.push(event);
 }
 
+void Client::handleCommand_MovePlayerRel(NetworkPacket *pkt)
+{
+	v3f added_pos;
+
+	*pkt >> added_pos;
+
+	LocalPlayer *player = m_env.getLocalPlayer();
+	assert(player);
+	player->addPosition(added_pos);
+}
+
 void Client::handleCommand_DeathScreen(NetworkPacket* pkt)
 {
 	bool set_camera_point_target;

src/network/networkprotocol.h

@@ -221,6 +221,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 		[scheduled bump for 5.8.0]
 	PROTOCOL VERSION 44:
 		AO_CMD_SET_BONE_POSITION extended
+		Add TOCLIENT_MOVE_PLAYER_REL
 		[scheduled bump for 5.9.0]
 */
 
@@ -835,6 +836,11 @@ enum ToClientCommand
 		f32 day_opacity
 	*/
 
+	TOCLIENT_MOVE_PLAYER_REL = 0x5d,
+	/*
+		v3f added_pos
+	*/
+
 	TOCLIENT_SRP_BYTES_S_B = 0x60,
 	/*
 		Belonging to AUTH_MECHANISM_SRP.

src/script/lua_api/l_object.cpp

@@ -134,6 +134,21 @@ int ObjectRef::l_set_pos(lua_State *L)
 	return 0;
 }
 
+// add_pos(self, pos)
+int ObjectRef::l_add_pos(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkObject<ObjectRef>(L, 1);
+	ServerActiveObject *sao = getobject(ref);
+	if (sao == nullptr)
+		return 0;
+
+	v3f pos = checkFloatPos(L, 2);
+
+	sao->addPos(pos);
+	return 0;
+}
+
 // move_to(self, pos, continuous)
 int ObjectRef::l_move_to(lua_State *L)
 {
@@ -2597,6 +2612,7 @@ luaL_Reg ObjectRef::methods[] = {
 	luamethod(ObjectRef, remove),
 	luamethod_aliased(ObjectRef, get_pos, getpos),
 	luamethod_aliased(ObjectRef, set_pos, setpos),
+	luamethod(ObjectRef, add_pos),
 	luamethod_aliased(ObjectRef, move_to, moveto),
 	luamethod(ObjectRef, punch),
 	luamethod(ObjectRef, right_click),

src/script/lua_api/l_object.h

@@ -73,6 +73,9 @@ private:
 	// set_pos(self, pos)
 	static int l_set_pos(lua_State *L);
 
+	// add_pos(self, pos)
+	static int l_add_pos(lua_State *L);
+
 	// move_to(self, pos, continuous)
 	static int l_move_to(lua_State *L);
 

src/server.cpp

@@ -1961,6 +1961,13 @@ void Server::SendMovePlayer(session_t peer_id)
 	Send(&pkt);
 }
 
+void Server::SendMovePlayerRel(session_t peer_id, const v3f &added_pos)
+{
+	NetworkPacket pkt(TOCLIENT_MOVE_PLAYER_REL, 0, peer_id);
+	pkt << added_pos;
+	Send(&pkt);
+}
+
 void Server::SendPlayerFov(session_t peer_id)
 {
 	NetworkPacket pkt(TOCLIENT_FOV, 4 + 1 + 4, peer_id);

src/server.h

@@ -364,6 +364,7 @@ public:
 	void SendPlayerBreath(PlayerSAO *sao);
 	void SendInventory(PlayerSAO *playerSAO, bool incremental);
 	void SendMovePlayer(session_t peer_id);
+	void SendMovePlayerRel(session_t peer_id, const v3f &added_pos);
 	void SendPlayerSpeed(session_t peer_id, const v3f &added_vel);
 	void SendPlayerFov(session_t peer_id);
 

src/server/player_sao.cpp

@@ -352,7 +352,7 @@ void PlayerSAO::setBasePosition(v3f position)
 
 void PlayerSAO::setPos(const v3f &pos)
 {
-	if(isAttached())
+	if (isAttached())
 		return;
 
 	// Send mapblock of target location
@@ -367,6 +367,30 @@ void PlayerSAO::setPos(const v3f &pos)
 	m_env->getGameDef()->SendMovePlayer(m_peer_id);
 }
 
+void PlayerSAO::addPos(const v3f &added_pos)
+{
+	if (isAttached())
+		return;
+
+	// Backward compatibility for older clients
+	if (m_player->protocol_version < 44) {
+		setPos(getBasePosition() + added_pos);
+		return;
+	}
+
+	// Send mapblock of target location
+	v3f pos = getBasePosition() + added_pos;
+	v3s16 blockpos = v3s16(pos.X / MAP_BLOCKSIZE, pos.Y / MAP_BLOCKSIZE, pos.Z / MAP_BLOCKSIZE);
+	m_env->getGameDef()->SendBlock(m_peer_id, blockpos);
+
+	setBasePosition(pos);
+	// Movement caused by this command is always valid
+	m_last_good_position = getBasePosition();
+	m_move_pool.empty();
+	m_time_from_last_teleport = 0.0;
+	m_env->getGameDef()->SendMovePlayerRel(m_peer_id, added_pos);
+}
+
 void PlayerSAO::moveTo(v3f pos, bool continuous)
 {
 	if(isAttached())

src/server/player_sao.h

@@ -90,6 +90,7 @@ public:
 	void step(float dtime, bool send_recommended) override;
 	void setBasePosition(v3f position);
 	void setPos(const v3f &pos) override;
+	void addPos(const v3f &added_pos) override;
 	void moveTo(v3f pos, bool continuous) override;
 	void setPlayerYaw(const float yaw);
 	// Data should not be sent at player initialization

src/server/serveractiveobject.h

@@ -91,6 +91,8 @@ public:
 
 	virtual void setPos(const v3f &pos)
 		{ setBasePosition(pos); }
+	virtual void addPos(const v3f &added_pos)
+		{ setBasePosition(m_base_position + added_pos); }
 	// continuous: if true, object does not stop immediately at pos
 	virtual void moveTo(v3f pos, bool continuous)
 		{ setBasePosition(pos); }