1. int num = 4500; 
2. Star stars[] = new Star[num]; 
3. 
   
4. void setup() { 
5.   size(800, 600, P3D); 
6.   smooth(); 
7.   for (int i=0; i< num; i++) { 
8.     stars[i] = new Star();
9.   } 
10.   frameRate(25);
11. } 
12. 
    
13. void draw() { 
14.   background(0);
15.   for (int i=0; i< num; i++) { 
16.     stars[i].display();
17.   }
18. } 
19. 
    
20. class Star { 
21.   float x = random(width); 
22.   float y = random(height); 
23.   float z = random(600); 
24.   int a = 0; 
25. 
    
26.   void display() {
27.     pushMatrix(); 
28.     translate(0, 0, z-100);
29.     stroke(0);
30.     box(0);
31.     stroke(255, a);
32.     line(x, y, z, x, y, z+45); 
33.     popMatrix(); 
34. 
    
35.     z+=random(10.0, 25.0); 
36.     //change alpha with z position 
37.     a+=z/20; 
38. 
    
39.     if (z>600) { 
40.       z=0; 
41.       a=0; 
42.       x = random(width); 
43.       y = random(height);
44.     }
45.   }
46. }

if you comment out box(0); (theoretically, it's useless) in the code, the effect will go wrong...

just a newbie practice of translation and rotation with bad expandability...

i believe there're better ways...

also I wonder if it's possible or not.

as you saw, I wrote the rect one by one, I know it's stupid, and it does have some clear patterns, but every time I try to put it into a for(), the image go weired...

help...