From 1b2c84da2eb7b2bc2aff3c11534bb39988167cb1 Mon Sep 17 00:00:00 2001
From: Yan <115050813@qq.com>
Date: Sun, 14 Jan 2018 18:08:23 +0800
Subject: [PATCH] [taken]Fix issue #764

Fix infinity loop in EmitterSphereShape. issue #764

I test on both method:

    public void getRandomPoint1(Vector3f store) {
        float l = FastMath.pow(FastMath.nextRandomFloat(), 1f / 3f);
        float u = FastMath.nextRandomFloat() * 2f - 1f;
        float o = FastMath.nextRandomFloat() * FastMath.TWO_PI;

        store.z = l * u;
        u = 1f / FastMath.fastInvSqrt(1f - u * u);
        store.x = l * u * FastMath.cos(o);
        store.y = l * u * FastMath.sin(o);
        store.multLocal(radius);
        store.addLocal(center);
    }

    public void getRandomPoint2(Vector3f store) {
        do {
            store.x = (FastMath.nextRandomFloat() * 2f - 1f);
            store.y = (FastMath.nextRandomFloat() * 2f - 1f);
            store.z = (FastMath.nextRandomFloat() * 2f - 1f);
        } while (store.lengthSquared() > 1);
        store.multLocal(radius);
        store.addLocal(center);
    }
    // Test
    public void testGetRandomPoint() {
        int n = 1000000;
        long start = System.nanoTime();
        for (int i = 0; i < n; i++) {
            getRandomPoint1(store);
        }
        long time1 = System.nanoTime() - start;

        start = System.nanoTime();
        for (int i = 0; i < n; i++) {
            getRandomPoint2(store);
        }
        long time2 = System.nanoTime() - start;

        System.out.println("t1:" + time1);
        System.out.println("t2:" + time2);
        System.out.println("t1/t2:" + (float) time1 / time2);
    }

Result:

    t1:352272158
    t2:94436324
    t1/t2:3.7302613

Method2 seems nearly 4 times faster than method1.
---
 .../com/jme3/effect/shapes/EmitterSphereShape.java     | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/jme3-core/src/main/java/com/jme3/effect/shapes/EmitterSphereShape.java b/jme3-core/src/main/java/com/jme3/effect/shapes/EmitterSphereShape.java
index 99d76205d..a74eeaf39 100644
--- a/jme3-core/src/main/java/com/jme3/effect/shapes/EmitterSphereShape.java
+++ b/jme3-core/src/main/java/com/jme3/effect/shapes/EmitterSphereShape.java
@@ -96,10 +96,12 @@ public class EmitterSphereShape implements EmitterShape {
     @Override
     public void getRandomPoint(Vector3f store) {
         do {
-            store.x = (FastMath.nextRandomFloat() * 2f - 1f) * radius;
-            store.y = (FastMath.nextRandomFloat() * 2f - 1f) * radius;
-            store.z = (FastMath.nextRandomFloat() * 2f - 1f) * radius;
-        } while (store.distance(center) > radius);
+            store.x = (FastMath.nextRandomFloat() * 2f - 1f);
+            store.y = (FastMath.nextRandomFloat() * 2f - 1f);
+            store.z = (FastMath.nextRandomFloat() * 2f - 1f);
+        } while (store.lengthSquared() > 1);
+        store.multLocal(radius);
+        store.addLocal(center);
     }
 
     @Override