From bea93daec3ad4e3345c701e5dcce250c44d128f2 Mon Sep 17 00:00:00 2001
From: Philipp Sehmisch <tmw@crushnet.org>
Date: Tue, 24 Jun 2008 12:29:33 +0000
Subject: Added particle property "follow-parent" which makes the particle move
 when its parent particle is moved.

---
 src/particle.cpp        | 12 ++++++++++++
 src/particle.h          | 19 +++++++++++++++++++
 src/particleemitter.cpp |  7 +++++++
 src/particleemitter.h   |  1 +
 4 files changed, 39 insertions(+)

(limited to 'src')

diff --git a/src/particle.cpp b/src/particle.cpp
index fd45430c..3b3f5116 100644
--- a/src/particle.cpp
+++ b/src/particle.cpp
@@ -63,6 +63,7 @@ Particle::Particle(Map *map):
     mGravity(0.0f),
     mRandomnes(0),
     mBounce(0.0f),
+    mFollow(false),
     mTarget(NULL),
     mAcceleration(0.0f),
     mInvDieDistance(-1.0f),
@@ -95,6 +96,8 @@ Particle::update()
         mAlive = false;
     }
 
+    Vector oldPos = mPos;
+
     if (mAlive)
     {
         //calculate particle movement
@@ -191,10 +194,19 @@ Particle::update()
         }
     }
 
+    Vector change = mPos - oldPos;
+
     // Update child particles
+
     for (ParticleIterator p = mChildParticles.begin();
          p != mChildParticles.end();)
     {
+        //move particle with its parent if desired
+        if ((*p)->doesFollow())
+        {
+            (*p)->moveBy(change);
+        }
+        //update particle
         if ((*p)->update())
         {
             p++;
diff --git a/src/particle.h b/src/particle.h
index 5ba2668b..88a38417 100644
--- a/src/particle.h
+++ b/src/particle.h
@@ -160,6 +160,10 @@ class Particle : public Sprite
         moveBy(float x, float y, float z)
         { mPos.x += x; mPos.y += y; mPos.z += z; }
 
+        void
+        moveBy (Vector change)
+        { mPos += change; }
+
         /**
          * Sets the time in game ticks until the particle is destroyed.
          */
@@ -234,6 +238,20 @@ class Particle : public Sprite
         setBounce(float bouncieness)
         { mBounce = bouncieness; }
 
+        /**
+         * Sets the flag if the particle is supposed to be moved by its parent
+         */
+        void
+        setFollow(bool follow)
+        { mFollow = follow; }
+
+        /**
+         * Gets the flag if the particle is supposed to be moved by its parent
+         */
+        bool
+        doesFollow()
+        { return mFollow; }
+
         /**
          * Makes the particle move toward another particle with a
          * given acceleration and momentum
@@ -287,6 +305,7 @@ class Particle : public Sprite
         float mGravity;             /**< Downward acceleration in pixels per game-tick. */
         int mRandomnes;             /**< Ammount of random vector change */
         float mBounce;              /**< How much the particle bounces off when hitting the ground */
+        bool mFollow;               /**< is this particle moved when its parent particle moves? */
 
         // follow-point particles
         Particle *mTarget;          /**< The particle that attracts this particle*/
diff --git a/src/particleemitter.cpp b/src/particleemitter.cpp
index 8f46c32b..631ca228 100644
--- a/src/particleemitter.cpp
+++ b/src/particleemitter.cpp
@@ -54,6 +54,7 @@ ParticleEmitter::ParticleEmitter(xmlNodePtr emitterNode, Particle *target, Map *
     mParticleGravity.set(0.0f);
     mParticleRandomnes.set(0);
     mParticleBounce.set(0.0f);
+    mParticleFollow = false;
     mParticleAcceleration.set(0.0f);
     mParticleDieDistance.set(-1.0f);
     mParticleMomentum.set(1.0f);
@@ -158,6 +159,10 @@ ParticleEmitter::ParticleEmitter(xmlNodePtr emitterNode, Particle *target, Map *
             {
                 mParticleAlpha = readMinMax(propertyNode, 1.0f);
             }
+            else if (name == "follow-parent")
+            {
+                mParticleFollow = true;
+            }
             else
             {
                 logger->log("Particle Engine: Warning, unknown emitter property \"%s\"",
@@ -258,6 +263,7 @@ ParticleEmitter & ParticleEmitter::operator=(const ParticleEmitter &o)
     mParticleGravity = o.mParticleGravity;
     mParticleRandomnes = o.mParticleRandomnes;
     mParticleBounce = o.mParticleBounce;
+    mParticleFollow = o.mParticleFollow;
     mParticleTarget = o.mParticleTarget;
     mParticleAcceleration = o.mParticleAcceleration;
     mParticleDieDistance = o.mParticleDieDistance;
@@ -339,6 +345,7 @@ ParticleEmitter::createParticles()
         newParticle->setRandomnes(mParticleRandomnes.value());
         newParticle->setGravity(mParticleGravity.value());
         newParticle->setBounce(mParticleBounce.value());
+        newParticle->setFollow(mParticleFollow);
 
         newParticle->setDestination(mParticleTarget,
                                     mParticleAcceleration.value(),
diff --git a/src/particleemitter.h b/src/particleemitter.h
index b7331527..2f45608d 100644
--- a/src/particleemitter.h
+++ b/src/particleemitter.h
@@ -99,6 +99,7 @@ class ParticleEmitter
         MinMax<float> mParticleGravity;
         MinMax<int> mParticleRandomnes;
         MinMax<float> mParticleBounce;
+        bool mParticleFollow;
 
         /*
          * Properties of targeting particles:
-- 
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