From d9199bf9ed4416adfccfa6fe089d2744b3483309 Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Fri, 28 Jun 2019 06:38:15 +0800
Subject: [PATCH] use range

---
 src/pixel/px_sphere.scad | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/pixel/px_sphere.scad b/src/pixel/px_sphere.scad
index c95709c5..3893630c 100644
--- a/src/pixel/px_sphere.scad
+++ b/src/pixel/px_sphere.scad
@@ -1,16 +1,17 @@
 function px_sphere(radius, filled = true) = 
+    let(range = [-radius: radius - 1])
     filled ? [
-        for(x = -radius; x < radius; x = x + 1)
-            for(y = -radius; y < radius; y = y + 1)        
-               for(z = -radius; z < radius; z = z + 1)
+        for(x = range)
+            for(y = range)        
+               for(z = range)
                    let(v = [x, y, z])
                    if(norm(v) < radius) v
     ] :
     let(ishell = radius * radius - 2 * radius)
     [
-        for(z = -radius; z < radius; z = z + 1)
-            for(y = -radius; y < radius; y = y + 1)        
-               for(x = -radius; x < radius; x = x + 1)
+        for(z = range)
+            for(y = range)        
+               for(x = range)
                    let(
                        v = [x, y, z],
                        leng = norm(v)