Particles: Add option to remove particles on collision

Adds the particle option `collision_removal = bool`

Some particles are hard to use right now since they either go through
solid blocks (without collision detection), and with collision
detection enabled they (e.g. raindrops) would just stop dead on the
floor and sit there until they expire, or worse, scrape along a wall
or ceiling.

We can solve the problem by adding a boolean flag that tells the
particle to be removed if it ever collides with something. This will
make it easier to add rain that doesn't fall through your roof or stick
on the top of it. Or clouds and smoke that don't go through trees.

Particles that collide with this flag are marked expired
unconditionally, causing them to be treated like normal expired
particles and cleaned up normally.

Documentation is adjusted accordingly.

An added bonus of this patch is that particles can potentially collide
many times with nodes, and this reduces the amount of collisions to 1
(max), which may end up reducing particle load on the client.

8 files changed, 78 insertions, 32 deletions

diff --git a/src/client.h b/src/client.h
index cdadb9d3e..a7eb22ad9 100644
--- a/src/client.h
+++ b/src/client.h
@@ -182,6 +182,7 @@ struct ClientEvent
 			f32 expirationtime;
 			f32 size;
 			bool collisiondetection;
+			bool collision_removal;
 			bool vertical;
 			std::string *texture;
 		} spawn_particle;
@@ -199,6 +200,7 @@ struct ClientEvent
 			f32 minsize;
 			f32 maxsize;
 			bool collisiondetection;
+			bool collision_removal;
 			bool vertical;
 			std::string *texture;
 			u32 id;
diff --git a/src/network/clientpackethandler.cpp b/src/network/clientpackethandler.cpp
index 0498f4048..48c573da5 100644
--- a/src/network/clientpackethandler.cpp
+++ b/src/network/clientpackethandler.cpp
@@ -898,8 +898,10 @@ void Client::handleCommand_SpawnParticle(NetworkPacket* pkt)
 	bool collisiondetection = readU8(is);
 	std::string texture     = deSerializeLongString(is);
 	bool vertical           = false;
+	bool collision_removal  = false;
 	try {
 		vertical = readU8(is);
+		collision_removal = readU8(is);
 	} catch (...) {}
 
 	ClientEvent event;
@@ -910,6 +912,7 @@ void Client::handleCommand_SpawnParticle(NetworkPacket* pkt)
 	event.spawn_particle.expirationtime     = expirationtime;
 	event.spawn_particle.size               = size;
 	event.spawn_particle.collisiondetection = collisiondetection;
+	event.spawn_particle.collision_removal  = collision_removal;
 	event.spawn_particle.vertical           = vertical;
 	event.spawn_particle.texture            = new std::string(texture);
 
@@ -942,8 +945,11 @@ void Client::handleCommand_AddParticleSpawner(NetworkPacket* pkt)
 	*pkt >> id;
 
 	bool vertical = false;
+	bool collision_removal = false;
 	try {
 		*pkt >> vertical;
+		*pkt >> collision_removal;
+
 	} catch (...) {}
 
 	ClientEvent event;
@@ -961,6 +967,7 @@ void Client::handleCommand_AddParticleSpawner(NetworkPacket* pkt)
 	event.add_particlespawner.minsize            = minsize;
 	event.add_particlespawner.maxsize            = maxsize;
 	event.add_particlespawner.collisiondetection = collisiondetection;
+	event.add_particlespawner.collision_removal  = collision_removal;
 	event.add_particlespawner.vertical           = vertical;
 	event.add_particlespawner.texture            = new std::string(texture);
 	event.add_particlespawner.id                 = id;
diff --git a/src/network/networkprotocol.h b/src/network/networkprotocol.h
index 177b97680..3a9483efb 100644
--- a/src/network/networkprotocol.h
+++ b/src/network/networkprotocol.h
@@ -474,6 +474,7 @@ enum ToClientCommand
 		u8 bool vertical
 		u32 len
 		u8[len] texture
+		u8 collision_removal
 	*/
 
 	TOCLIENT_ADD_PARTICLESPAWNER = 0x47,
@@ -495,6 +496,7 @@ enum ToClientCommand
 		u32 len
 		u8[len] texture
 		u32 id
+		u8 collision_removal
 	*/
 
 	TOCLIENT_DELETE_PARTICLESPAWNER_LEGACY = 0x48,
diff --git a/src/particles.cpp b/src/particles.cpp
index 525258a25..ccca691d1 100644
--- a/src/particles.cpp
+++ b/src/particles.cpp
@@ -54,6 +54,7 @@ Particle::Particle(
 	float expirationtime,
 	float size,
 	bool collisiondetection,
+	bool collision_removal,
 	bool vertical,
 	video::ITexture *texture,
 	v2f texpos,
@@ -85,6 +86,7 @@ Particle::Particle(
 	m_player = player;
 	m_size = size;
 	m_collisiondetection = collisiondetection;
+	m_collision_removal = collision_removal;
 	m_vertical = vertical;
 
 	// Irrlicht stuff
@@ -126,20 +128,21 @@ void Particle::render()
 void Particle::step(float dtime)
 {
 	m_time += dtime;
-	if (m_collisiondetection)
-	{
+	if (m_collisiondetection) {
 		aabb3f box = m_collisionbox;
-		v3f p_pos = m_pos*BS;
-		v3f p_velocity = m_velocity*BS;
-		collisionMoveSimple(m_env, m_gamedef,
-			BS*0.5, box,
-			0, dtime,
-			&p_pos, &p_velocity, m_acceleration * BS);
-		m_pos = p_pos/BS;
-		m_velocity = p_velocity/BS;
-	}
-	else
-	{
+		v3f p_pos = m_pos * BS;
+		v3f p_velocity = m_velocity * BS;
+		collisionMoveResult r = collisionMoveSimple(m_env,
+			m_gamedef, BS * 0.5, box, 0, dtime, &p_pos,
+			&p_velocity, m_acceleration * BS);
+		if (m_collision_removal && r.collides) {
+			// force expiration of the particle
+			m_expiration = -1.0;
+		} else {
+			m_pos = p_pos / BS;
+			m_velocity = p_velocity / BS;
+		}
+	} else {
 		m_velocity += m_acceleration * dtime;
 		m_pos += m_velocity * dtime;
 	}
@@ -210,8 +213,8 @@ ParticleSpawner::ParticleSpawner(IGameDef* gamedef, scene::ISceneManager *smgr,
 	u16 amount, float time,
 	v3f minpos, v3f maxpos, v3f minvel, v3f maxvel, v3f minacc, v3f maxacc,
 	float minexptime, float maxexptime, float minsize, float maxsize,
-	bool collisiondetection, bool vertical, video::ITexture *texture, u32 id,
-	ParticleManager *p_manager) :
+	bool collisiondetection, bool collision_removal, bool vertical,
+	video::ITexture *texture, u32 id, ParticleManager *p_manager) :
 	m_particlemanager(p_manager)
 {
 	m_gamedef = gamedef;
@@ -230,6 +233,7 @@ ParticleSpawner::ParticleSpawner(IGameDef* gamedef, scene::ISceneManager *smgr,
 	m_minsize = minsize;
 	m_maxsize = maxsize;
 	m_collisiondetection = collisiondetection;
+	m_collision_removal = collision_removal;
 	m_vertical = vertical;
 	m_texture = texture;
 	m_time = 0;
@@ -277,6 +281,7 @@ void ParticleSpawner::step(float dtime, ClientEnvironment* env)
 					exptime,
 					size,
 					m_collisiondetection,
+					m_collision_removal,
 					m_vertical,
 					m_texture,
 					v2f(0.0, 0.0),
@@ -317,6 +322,7 @@ void ParticleSpawner::step(float dtime, ClientEnvironment* env)
 					exptime,
 					size,
 					m_collisiondetection,
+					m_collision_removal,
 					m_vertical,
 					m_texture,
 					v2f(0.0, 0.0),
@@ -446,6 +452,7 @@ void ParticleManager::handleParticleEvent(ClientEvent *event, IGameDef *gamedef,
 					event->add_particlespawner.minsize,
 					event->add_particlespawner.maxsize,
 					event->add_particlespawner.collisiondetection,
+					event->add_particlespawner.collision_removal,
 					event->add_particlespawner.vertical,
 					texture,
 					event->add_particlespawner.id,
@@ -480,6 +487,7 @@ void ParticleManager::handleParticleEvent(ClientEvent *event, IGameDef *gamedef,
 					event->spawn_particle.expirationtime,
 					event->spawn_particle.size,
 					event->spawn_particle.collisiondetection,
+					event->spawn_particle.collision_removal,
 					event->spawn_particle.vertical,
 					texture,
 					v2f(0.0, 0.0),
@@ -555,6 +563,7 @@ void ParticleManager::addNodeParticle(IGameDef* gamedef, scene::ISceneManager* s
 		visual_size,
 		true,
 		false,
+		false,
 		texture,
 		texpos,
 		texsize);
diff --git a/src/particles.h b/src/particles.h
index dda84385c..bc3ca53b7 100644
--- a/src/particles.h
+++ b/src/particles.h
@@ -30,6 +30,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 struct ClientEvent;
 class ParticleManager;
+class ClientEnvironment;
 
 class Particle : public scene::ISceneNode
 {
@@ -45,6 +46,7 @@ class Particle : public scene::ISceneNode
 		float expirationtime,
 		float size,
 		bool collisiondetection,
+		bool collision_removal,
 		bool vertical,
 		video::ITexture *texture,
 		v2f texpos,
@@ -97,6 +99,7 @@ private:
 	float m_size;
 	u8 m_light;
 	bool m_collisiondetection;
+	bool m_collision_removal;
 	bool m_vertical;
 	v3s16 m_camera_offset;
 };
@@ -115,6 +118,7 @@ class ParticleSpawner
 		float minexptime, float maxexptime,
 		float minsize, float maxsize,
 		bool collisiondetection,
+		bool collision_removal,
 		bool vertical,
 		video::ITexture *texture,
 		u32 id,
@@ -148,6 +152,7 @@ class ParticleSpawner
 	video::ITexture *m_texture;
 	std::vector<float> m_spawntimes;
 	bool m_collisiondetection;
+	bool m_collision_removal;
 	bool m_vertical;
 
 };
diff --git a/src/script/lua_api/l_particles.cpp b/src/script/lua_api/l_particles.cpp
index f6c1725de..263e35407 100644
--- a/src/script/lua_api/l_particles.cpp
+++ b/src/script/lua_api/l_particles.cpp
@@ -21,13 +21,16 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "lua_api/l_internal.h"
 #include "common/c_converter.h"
 #include "server.h"
+#include "particles.h"
 
 // add_particle({pos=, velocity=, acceleration=, expirationtime=,
-// 		size=, collisiondetection=, vertical=, texture=, player=})
+// 		size=, collisiondetection=, collision_removal=, vertical=,
+//		texture=, player=})
 // pos/velocity/acceleration = {x=num, y=num, z=num}
 // expirationtime = num (seconds)
 // size = num
 // collisiondetection = bool
+// collision_removal = bool
 // vertical = bool
 // texture = e.g."default_wood.png"
 int ModApiParticles::l_add_particle(lua_State *L)
@@ -41,8 +44,8 @@ int ModApiParticles::l_add_particle(lua_State *L)
 	float expirationtime, size;
 	expirationtime = size = 1;
 
-	bool collisiondetection, vertical;
-	collisiondetection = vertical = false;
+	bool collisiondetection, vertical, collision_removal;
+	collisiondetection = vertical = collision_removal = false;
 
 	std::string texture = "";
 	std::string playername = "";
@@ -94,12 +97,14 @@ int ModApiParticles::l_add_particle(lua_State *L)
 		size = getfloatfield_default(L, 1, "size", 1);
 		collisiondetection = getboolfield_default(L, 1,
 			"collisiondetection", collisiondetection);
+		collision_removal = getboolfield_default(L, 1,
+			"collision_removal", collision_removal);
 		vertical = getboolfield_default(L, 1, "vertical", vertical);
 		texture = getstringfield_default(L, 1, "texture", "");
 		playername = getstringfield_default(L, 1, "playername", "");
 	}
-	getServer(L)->spawnParticle(playername, pos, vel, acc,
-			expirationtime, size, collisiondetection, vertical, texture);
+	getServer(L)->spawnParticle(playername, pos, vel, acc, expirationtime, size,
+			collisiondetection, collision_removal, vertical, texture);
 	return 1;
 }
 
@@ -110,6 +115,7 @@ int ModApiParticles::l_add_particle(lua_State *L)
 //				minexptime=, maxexptime=,
 //				minsize=, maxsize=,
 //				collisiondetection=,
+//				collision_removal=,
 //				vertical=,
 //				texture=,
 //				player=})
@@ -117,6 +123,7 @@ int ModApiParticles::l_add_particle(lua_State *L)
 // minexptime/maxexptime = num (seconds)
 // minsize/maxsize = num
 // collisiondetection = bool
+// collision_removal = bool
 // vertical = bool
 // texture = e.g."default_wood.png"
 int ModApiParticles::l_add_particlespawner(lua_State *L)
@@ -129,8 +136,8 @@ int ModApiParticles::l_add_particlespawner(lua_State *L)
 	    minpos= maxpos= minvel= maxvel= minacc= maxacc= v3f(0, 0, 0);
 	float time, minexptime, maxexptime, minsize, maxsize;
 	      time= minexptime= maxexptime= minsize= maxsize= 1;
-	bool collisiondetection, vertical;
-	     collisiondetection= vertical= false;
+	bool collisiondetection, vertical, collision_removal;
+	     collisiondetection = vertical = collision_removal = false;
 	std::string texture = "";
 	std::string playername = "";
 
@@ -189,6 +196,8 @@ int ModApiParticles::l_add_particlespawner(lua_State *L)
 		maxsize = getfloatfield_default(L, 1, "maxsize", maxsize);
 		collisiondetection = getboolfield_default(L, 1,
 			"collisiondetection", collisiondetection);
+		collision_removal = getboolfield_default(L, 1,
+			"collision_removal", collision_removal);
 		vertical = getboolfield_default(L, 1, "vertical", vertical);
 		texture = getstringfield_default(L, 1, "texture", "");
 		playername = getstringfield_default(L, 1, "playername", "");
@@ -201,6 +210,7 @@ int ModApiParticles::l_add_particlespawner(lua_State *L)
 			minexptime, maxexptime,
 			minsize, maxsize,
 			collisiondetection,
+			collision_removal,
 			vertical,
 			texture, playername);
 	lua_pushnumber(L, id);
diff --git a/src/server.cpp b/src/server.cpp
index a3b686c25..ada45dc68 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -1673,7 +1673,8 @@ void Server::SendShowFormspecMessage(u16 peer_id, const std::string &formspec,
 // Spawns a particle on peer with peer_id
 void Server::SendSpawnParticle(u16 peer_id, v3f pos, v3f velocity, v3f acceleration,
 				float expirationtime, float size, bool collisiondetection,
-				bool vertical, std::string texture)
+				bool collision_removal,
+				bool vertical, const std::string &texture)
 {
 	DSTACK(FUNCTION_NAME);
 
@@ -1683,6 +1684,7 @@ void Server::SendSpawnParticle(u16 peer_id, v3f pos, v3f velocity, v3f accelerat
 			<< size << collisiondetection;
 	pkt.putLongString(texture);
 	pkt << vertical;
+	pkt << collision_removal;
 
 	if (peer_id != PEER_ID_INEXISTENT) {
 		Send(&pkt);
@@ -1695,7 +1697,8 @@ void Server::SendSpawnParticle(u16 peer_id, v3f pos, v3f velocity, v3f accelerat
 // Adds a ParticleSpawner on peer with peer_id
 void Server::SendAddParticleSpawner(u16 peer_id, u16 amount, float spawntime, v3f minpos, v3f maxpos,
 	v3f minvel, v3f maxvel, v3f minacc, v3f maxacc, float minexptime, float maxexptime,
-	float minsize, float maxsize, bool collisiondetection, bool vertical, std::string texture, u32 id)
+	float minsize, float maxsize, bool collisiondetection, bool collision_removal,
+	bool vertical, const std::string &texture, u32 id)
 {
 	DSTACK(FUNCTION_NAME);
 
@@ -1708,6 +1711,7 @@ void Server::SendAddParticleSpawner(u16 peer_id, u16 amount, float spawntime, v3
 	pkt.putLongString(texture);
 
 	pkt << id << vertical;
+	pkt << collision_removal;
 
 	if (peer_id != PEER_ID_INEXISTENT) {
 		Send(&pkt);
@@ -3160,7 +3164,8 @@ void Server::notifyPlayers(const std::wstring &msg)
 void Server::spawnParticle(const std::string &playername, v3f pos,
 	v3f velocity, v3f acceleration,
 	float expirationtime, float size, bool
-	collisiondetection, bool vertical, const std::string &texture)
+	collisiondetection, bool collision_removal,
+	bool vertical, const std::string &texture)
 {
 	// m_env will be NULL if the server is initializing
 	if (!m_env)
@@ -3175,13 +3180,15 @@ void Server::spawnParticle(const std::string &playername, v3f pos,
 	}
 
 	SendSpawnParticle(peer_id, pos, velocity, acceleration,
-			expirationtime, size, collisiondetection, vertical, texture);
+			expirationtime, size, collisiondetection,
+			collision_removal, vertical, texture);
 }
 
 u32 Server::addParticleSpawner(u16 amount, float spawntime,
 	v3f minpos, v3f maxpos, v3f minvel, v3f maxvel, v3f minacc, v3f maxacc,
 	float minexptime, float maxexptime, float minsize, float maxsize,
-	bool collisiondetection, bool vertical, const std::string &texture,
+	bool collisiondetection, bool collision_removal,
+	bool vertical, const std::string &texture,
 	const std::string &playername)
 {
 	// m_env will be NULL if the server is initializing
@@ -3200,7 +3207,7 @@ u32 Server::addParticleSpawner(u16 amount, float spawntime,
 	SendAddParticleSpawner(peer_id, amount, spawntime,
 		minpos, maxpos, minvel, maxvel, minacc, maxacc,
 		minexptime, maxexptime, minsize, maxsize,
-		collisiondetection, vertical, texture, id);
+		collisiondetection, collision_removal, vertical, texture, id);
 
 	return id;
 }
diff --git a/src/server.h b/src/server.h
index daf51dee1..7ee15a463 100644
--- a/src/server.h
+++ b/src/server.h
@@ -275,7 +275,8 @@ public:
 	void spawnParticle(const std::string &playername,
 		v3f pos, v3f velocity, v3f acceleration,
 		float expirationtime, float size,
-		bool collisiondetection, bool vertical, const std::string &texture);
+		bool collisiondetection, bool collision_removal,
+		bool vertical, const std::string &texture);
 
 	u32 addParticleSpawner(u16 amount, float spawntime,
 		v3f minpos, v3f maxpos,
@@ -283,7 +284,8 @@ public:
 		v3f minacc, v3f maxacc,
 		float minexptime, float maxexptime,
 		float minsize, float maxsize,
-		bool collisiondetection, bool vertical, const std::string &texture,
+		bool collisiondetection, bool collision_removal,
+		bool vertical, const std::string &texture,
 		const std::string &playername);
 
 	void deleteParticleSpawner(const std::string &playername, u32 id);
@@ -456,7 +458,8 @@ private:
 		v3f minacc, v3f maxacc,
 		float minexptime, float maxexptime,
 		float minsize, float maxsize,
-		bool collisiondetection, bool vertical, std::string texture, u32 id);
+		bool collisiondetection, bool collision_removal,
+		bool vertical, const std::string &texture, u32 id);
 
 	void SendDeleteParticleSpawner(u16 peer_id, u32 id);
 
@@ -464,7 +467,8 @@ private:
 	void SendSpawnParticle(u16 peer_id,
 		v3f pos, v3f velocity, v3f acceleration,
 		float expirationtime, float size,
-		bool collisiondetection, bool vertical, std::string texture);
+		bool collisiondetection, bool collision_removal,
+		bool vertical, const std::string &texture);
 
 	u32 SendActiveObjectRemoveAdd(u16 peer_id, const std::string &datas);
 	void SendActiveObjectMessages(u16 peer_id, const std::string &datas, bool reliable = true);