Hi,

I'm quite new to Processing and programming and have come across a problem that I was hoping someone may be kind enough to help me with.

I'm using an embedded "for" loop to create a matrix of circles which works o.k in the following example:

Code:

 

size (500,500);
stroke(0);
smooth();
int f=0;
int direction=1;
for(int x=25; x<500; x=x+50){
  for(int y=25; y<500; y=y+50){
    fill(f=f+25*direction);
	 ellipse (x,y,20,20);
    if (f>=255||f<=0){
	direction=direction*-1;
    }}}
      

However, the next stage of the experiment fails when I attempt to make the distance between the centre point of the ellipses decrease by introducing a new variable into the loop as follows:

Code:

 

size (500,500);
stroke(0);
smooth();
int f=0;
int g=0;
int direction=1;
for(int x=25; x<500; x=x+50-g){
  for(int y=25; y<500; y=y+50-g){
    fill(f=f+25*direction);
	 ellipse (x,y,20,20);
g=g+5;
    if (f>=255||f<=0){
	direction=direction*-1;
    }}}
      

Running this code causes Processing to freeze, without any error message. I'm guessing that introducing another variable into the loop causes some sort of badness that I don't understand.

If someone could explain or offer a more elegant( and functional) solution, I'd appreciate it.

Processing is freezing b/c it is stuck in an infinite loop.  You start with g equal to 0, so:

g = 0;
y = 25;
if y < 500 loop
y = 25 + 50 - 0 --> 75

Then: g = g + 5, so g = 5;

g = 5;
y = 75;
if y < 500 loop
y = 75 + 50 - 5 --> 120

After a while (10 times), g will equal 50.

g = 50;
y = 250;
if y < 500 loop
y = 250 + 50 - 50 --> 250

The loop will not stop since y will never become larger than 500.  One solution would simply be to constrain the value of g:

Code:

g = constrain(g,0,49);