Implement adding velocity to player from Lua

The intended usecase is knockback, but there's potential for more.

doc/lua_api.txt

@@ -5465,6 +5465,14 @@ This is basically a reference to a C++ `ServerActiveObject`
 * `get_player_name()`: returns `""` if is not a player
 * `get_player_velocity()`: returns `nil` if is not a player, otherwise a
   table {x, y, z} representing the player's instantaneous velocity in nodes/s
+* `add_player_velocity(vel)`
+    * Adds to player velocity, this happens client-side and only once.
+    * 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.
+    * Example: `add_player_velocity({x=0, y=6.5, z=0})` is equivalent to
+      pressing the jump key (assuming default settings)
 * `get_look_dir()`: get camera direction as a unit vector
 * `get_look_vertical()`: pitch in radians
     * Angle ranges between -pi/2 and pi/2, which are straight up and down

src/client/client.h

@@ -227,6 +227,7 @@ public:
 	void handleCommand_SrpBytesSandB(NetworkPacket *pkt);
 	void handleCommand_FormspecPrepend(NetworkPacket *pkt);
 	void handleCommand_CSMRestrictionFlags(NetworkPacket *pkt);
+	void handleCommand_PlayerSpeed(NetworkPacket *pkt);
 
 	void ProcessData(NetworkPacket *pkt);
 

src/client/localplayer.cpp

@@ -188,6 +188,7 @@ void LocalPlayer::move(f32 dtime, Environment *env, f32 pos_max_d,
 	// Copy parent position if local player is attached
 	if (isAttached) {
 		setPosition(overridePosition);
+		added_velocity = v3f(); // ignored
 		return;
 	}
 
@@ -201,9 +202,13 @@ void LocalPlayer::move(f32 dtime, Environment *env, f32 pos_max_d,
 	if (noclip && free_move) {
 		position += m_speed * dtime;
 		setPosition(position);
+		added_velocity = v3f(); // ignored
 		return;
 	}
 
+	m_speed += added_velocity;
+	added_velocity = v3f();
+
 	/*
 		Collision detection
 	*/
@@ -782,6 +787,7 @@ void LocalPlayer::old_move(f32 dtime, Environment *env, f32 pos_max_d,
 	if (isAttached) {
 		setPosition(overridePosition);
 		m_sneak_node_exists = false;
+		added_velocity = v3f();
 		return;
 	}
 
@@ -795,9 +801,13 @@ void LocalPlayer::old_move(f32 dtime, Environment *env, f32 pos_max_d,
 		position += m_speed * dtime;
 		setPosition(position);
 		m_sneak_node_exists = false;
+		added_velocity = v3f();
 		return;
 	}
 
+	m_speed += added_velocity;
+	added_velocity = v3f();
+
 	/*
 		Collision detection
 	*/

src/client/localplayer.h

@@ -149,6 +149,11 @@ public:
 
 	bool getAutojump() const { return m_autojump; }
 
+	inline void addVelocity(const v3f &vel)
+	{
+		added_velocity += vel;
+	}
+
 private:
 	void accelerate(const v3f &target_speed, const f32 max_increase_H,
 			const f32 max_increase_V, const bool use_pitch);
@@ -194,6 +199,7 @@ private:
 	float m_zoom_fov = 0.0f;
 	bool m_autojump = false;
 	float m_autojump_time = 0.0f;
+	v3f added_velocity = v3f(0.0f, 0.0f, 0.0f); // cleared on each move()
 
 	GenericCAO *m_cao = nullptr;
 	Client *m_client;

src/content_sao.cpp

@@ -1091,6 +1091,7 @@ void PlayerSAO::step(float dtime, bool send_recommended)
 	m_time_from_last_teleport += dtime;
 	m_time_from_last_punch += dtime;
 	m_nocheat_dig_time += dtime;
+	m_max_speed_override_time = MYMAX(m_max_speed_override_time - dtime, 0.0f);
 
 	// Each frame, parent position is copied if the object is attached,
 	// otherwise it's calculated normally.
@@ -1412,6 +1413,19 @@ std::string PlayerSAO::getPropertyPacket()
 	return gob_cmd_set_properties(m_prop);
 }
 
+void PlayerSAO::setMaxSpeedOverride(const v3f &vel)
+{
+	if (m_max_speed_override_time == 0.0f)
+		m_max_speed_override = vel;
+	else
+		m_max_speed_override += vel;
+	if (m_player) {
+		float accel = MYMIN(m_player->movement_acceleration_default,
+				m_player->movement_acceleration_air);
+		m_max_speed_override_time = m_max_speed_override.getLength() / accel / BS;
+	}
+}
+
 bool PlayerSAO::checkMovementCheat()
 {
 	if (isAttached() || m_is_singleplayer ||
@@ -1431,6 +1445,14 @@ bool PlayerSAO::checkMovementCheat()
 		too, and much more lightweight.
 	*/
 
+	float override_max_H, override_max_V;
+	if (m_max_speed_override_time > 0.0f) {
+		override_max_H = MYMAX(fabs(m_max_speed_override.X), fabs(m_max_speed_override.Z));
+		override_max_V = fabs(m_max_speed_override.Y);
+	} else {
+		override_max_H = override_max_V = 0.0f;
+	}
+
 	float player_max_walk = 0; // horizontal movement
 	float player_max_jump = 0; // vertical upwards movement
 
@@ -1439,10 +1461,13 @@ bool PlayerSAO::checkMovementCheat()
 	else
 		player_max_walk = m_player->movement_speed_walk; // Normal speed
 	player_max_walk *= m_physics_override_speed;
+	player_max_walk = MYMAX(player_max_walk, override_max_H);
+
 	player_max_jump = m_player->movement_speed_jump * m_physics_override_jump;
 	// FIXME: Bouncy nodes cause practically unbound increase in Y speed,
 	//        until this can be verified correctly, tolerate higher jumping speeds
 	player_max_jump *= 2.0;
+	player_max_jump = MYMAX(player_max_jump, override_max_V);
 
 	// Don't divide by zero!
 	if (player_max_walk < 0.0001f)

src/content_sao.h

@@ -322,6 +322,7 @@ public:
 	{
 		return m_dig_pool;
 	}
+	void setMaxSpeedOverride(const v3f &vel);
 	// Returns true if cheated
 	bool checkMovementCheat();
 
@@ -361,6 +362,8 @@ private:
 	float m_time_from_last_punch = 0.0f;
 	v3s16 m_nocheat_dig_pos = v3s16(32767, 32767, 32767);
 	float m_nocheat_dig_time = 0.0f;
+	float m_max_speed_override_time = 0.0f;
+	v3f m_max_speed_override = v3f(0.0f, 0.0f, 0.0f);
 
 	// Timers
 	IntervalLimiter m_breathing_interval;

src/network/clientopcodes.cpp

@@ -67,7 +67,7 @@ const ToClientCommandHandler toClientCommandTable[TOCLIENT_NUM_MSG_TYPES] =
 	null_command_handler,
 	{ "TOCLIENT_TIME_OF_DAY",              TOCLIENT_STATE_CONNECTED, &Client::handleCommand_TimeOfDay }, // 0x29
 	{ "TOCLIENT_CSM_RESTRICTION_FLAGS",    TOCLIENT_STATE_CONNECTED, &Client::handleCommand_CSMRestrictionFlags }, // 0x2A
-	null_command_handler,
+	{ "TOCLIENT_PLAYER_SPEED",             TOCLIENT_STATE_CONNECTED, &Client::handleCommand_PlayerSpeed }, // 0x2B
 	null_command_handler,
 	null_command_handler,
 	null_command_handler,

src/network/clientpackethandler.cpp

@@ -1383,6 +1383,17 @@ void Client::handleCommand_CSMRestrictionFlags(NetworkPacket *pkt)
 	loadMods();
 }
 
+void Client::handleCommand_PlayerSpeed(NetworkPacket *pkt)
+{
+	v3f added_vel;
+
+	*pkt >> added_vel;
+
+	LocalPlayer *player = m_env.getLocalPlayer();
+	assert(player != NULL);
+	player->addVelocity(added_vel);
+}
+
 /*
  * Mod channels
  */

src/network/networkprotocol.h

@@ -194,6 +194,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 		New network float format
 		ContentFeatures version 13
 		Add full Euler rotations instead of just yaw
+		Add TOCLIENT_PLAYER_SPEED
 */
 
 #define LATEST_PROTOCOL_VERSION 37
@@ -295,6 +296,11 @@ enum ToClientCommand
 		u32 CSMRestrictionFlags byteflag
 	 */
 
+	TOCLIENT_PLAYER_SPEED = 0x2B,
+	/*
+		v3f added_vel
+	 */
+
 	// (oops, there is some gap here)
 
 	TOCLIENT_CHAT_MESSAGE = 0x2F,

src/network/serveropcodes.cpp

@@ -156,7 +156,7 @@ const ClientCommandFactory clientCommandFactoryTable[TOCLIENT_NUM_MSG_TYPES] =
 	null_command_factory,
 	{ "TOCLIENT_TIME_OF_DAY",              0, true }, // 0x29
 	{ "TOCLIENT_CSM_RESTRICTION_FLAGS",    0, true }, // 0x2A
-	null_command_factory,
+	{ "TOCLIENT_PLAYER_SPEED",             0, true }, // 0x2B
 	null_command_factory,
 	null_command_factory,
 	null_command_factory,

src/script/lua_api/l_object.cpp

@@ -1092,6 +1092,27 @@ int ObjectRef::l_get_player_velocity(lua_State *L)
 	return 1;
 }
 
+// add_player_velocity(self, {x=num, y=num, z=num})
+int ObjectRef::l_add_player_velocity(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkobject(L, 1);
+	v3f vel = checkFloatPos(L, 2);
+
+	RemotePlayer *player = getplayer(ref);
+	PlayerSAO *co = getplayersao(ref);
+	if (!player || !co)
+		return 0;
+
+	session_t peer_id = player->getPeerId();
+	if (peer_id == PEER_ID_INEXISTENT)
+		return 0;
+	// Do it
+	co->setMaxSpeedOverride(vel);
+	getServer(L)->SendPlayerSpeed(peer_id, vel);
+	return 0;
+}
+
 // get_look_dir(self)
 int ObjectRef::l_get_look_dir(lua_State *L)
 {
@@ -1931,6 +1952,7 @@ luaL_Reg ObjectRef::methods[] = {
 	luamethod(ObjectRef, is_player_connected),
 	luamethod(ObjectRef, get_player_name),
 	luamethod(ObjectRef, get_player_velocity),
+	luamethod(ObjectRef, add_player_velocity),
 	luamethod(ObjectRef, get_look_dir),
 	luamethod(ObjectRef, get_look_pitch),
 	luamethod(ObjectRef, get_look_yaw),

src/script/lua_api/l_object.h

@@ -212,6 +212,9 @@ private:
 	// get_player_velocity(self)
 	static int l_get_player_velocity(lua_State *L);
 
+	// add_player_velocity(self, {x=num, y=num, z=num})
+	static int l_add_player_velocity(lua_State *L);
+
 	// get_look_dir(self)
 	static int l_get_look_dir(lua_State *L);
 

src/server.cpp

@@ -1958,6 +1958,13 @@ void Server::SendCSMRestrictionFlags(session_t peer_id)
 	Send(&pkt);
 }
 
+void Server::SendPlayerSpeed(session_t peer_id, const v3f &added_vel)
+{
+	NetworkPacket pkt(TOCLIENT_PLAYER_SPEED, 0, peer_id);
+	pkt << added_vel;
+	Send(&pkt);
+}
+
 s32 Server::playSound(const SimpleSoundSpec &spec,
 		const ServerSoundParams &params)
 {

src/server.h

@@ -335,6 +335,7 @@ public:
 	void SendPlayerBreath(PlayerSAO *sao);
 	void SendInventory(PlayerSAO* playerSAO);
 	void SendMovePlayer(session_t peer_id);
+	void SendPlayerSpeed(session_t peer_id, const v3f &added_vel);
 
 	virtual bool registerModStorage(ModMetadata *storage);
 	virtual void unregisterModStorage(const std::string &name);