From 6075e4639d3c15f7ed497db13c5a60aeeb282b82 Mon Sep 17 00:00:00 2001
From: William Linna <william.linna@openmailbox.org>
Date: Sat, 14 Nov 2015 16:19:54 +0200
Subject: [PATCH 1/2] Interpolate particle positions

NOTE: This change is not invented by me. All credit goes to methusalah.
See this thread:
http://hub.jmonkeyengine.org/t/interpolation-of-particle-spawning-point/30385/7
---
 .../main/java/com/jme3/effect/ParticleEmitter.java    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java b/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
index 28bfd595d..6a05e359c 100644
--- a/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
+++ b/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
@@ -106,6 +106,7 @@ public class ParticleEmitter extends Geometry {
     private boolean worldSpace = true;
     //variable that helps with computations
     private transient Vector3f temp = new Vector3f();
+    private transient Vector3f lastPos;
 
     public static class ParticleEmitterControl implements Control {
 
@@ -1013,12 +1014,16 @@ public class ParticleEmitter extends Geometry {
         
         // Spawns particles within the tpf timeslot with proper age
         float interval = 1f / particlesPerSec;
+        float originalTpf = tpf;
         tpf += timeDifference;
         while (tpf > interval){
             tpf -= interval;
             Particle p = emitParticle(min, max);
             if (p != null){
                 p.life -= tpf;
+                if (lastPos != null) {
+                    p.position.interpolateLocal(lastPos, 1 - tpf / originalTpf);
+                }
                 if (p.life <= 0){
                     freeParticle(lastUsed);
                 }else{
@@ -1028,6 +1033,12 @@ public class ParticleEmitter extends Geometry {
         }
         timeDifference = tpf;
 
+        if (lastPos == null) {
+            lastPos = new Vector3f();
+        }
+
+        lastPos.set(getWorldTranslation());
+
         BoundingBox bbox = (BoundingBox) this.getMesh().getBound();
         bbox.setMinMax(min, max);
         this.setBoundRefresh();

From c8a16c940f877728198f7da8e976cd117432b51e Mon Sep 17 00:00:00 2001
From: William Linna <william.linna@openmailbox.org>
Date: Sat, 14 Nov 2015 16:32:44 +0200
Subject: [PATCH 2/2] Only interpolate if particles are in world space

---
 jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java b/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
index 6a05e359c..ca3467781 100644
--- a/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
+++ b/jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java
@@ -1021,7 +1021,7 @@ public class ParticleEmitter extends Geometry {
             Particle p = emitParticle(min, max);
             if (p != null){
                 p.life -= tpf;
-                if (lastPos != null) {
+                if (lastPos != null && isInWorldSpace()) {
                     p.position.interpolateLocal(lastPos, 1 - tpf / originalTpf);
                 }
                 if (p.life <= 0){