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.

1 files changed, 24 insertions, 15 deletions

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);