Here is a custom function you can use. You enter the maximum value as the first parameter. It will count from 0 to max and back to 0 etc. With the second parameter you can control the speed (aka the number of times it will return each count).

Code Example

1. void draw() {
2.   int value = upDownCounter(5, 1);
3.   printl(value);
4. }
5. 
   
6. int upDownCounter(int maxValue, int factor) {
7.   int doubleMaxValue = 2*maxValue;
8.   int fcd = (frameCount/factor)%doubleMaxValue;
9.   return (fcd<maxValue)?fcd:doubleMaxValue-fcd;
10. }

Also you might be interested by the map() function.

Hey guys, thanks for the replies but I'm having trouble fitting that custom function into the code without getting a load of different errors. I'm assuming that the code would appear straight after void draw() { so that the function got instigated first before any manipulation of numbers occurred. The issue I have no idea how to get the upDownCounter to be implemented on a specific number that's counting i.e. mins.

Also it keeps telling me that I have some unreachable code in the program but I can't figure out which part of the function would stop my code from working.

Any help?

1. float angle = 0;
   float px = 0, py = 0;
   float amplitude = 30;
   float frequency = 0;
   float fillGap = 2.5;
   int m;
   int m2;
   int m3;
   int mins;
   int mins10;
   color c;
   
   void setup() {
     size(500, 500);
     background(200);
    
    
    
   }
   
   void draw() {
    
      int value = upDownCounter(225, 2);
     println(value);
   }
   
   int upDownCounter(int maxValue, int factor) {
     int doubleMaxValue = factor*maxValue;
     int fcd = (frameCount/factor)%doubleMaxValue;
     return (fcd<225)?fcd:doubleMaxValue-fcd;
   
    
     m = millis() / 100;
     m2 = millis() / 1000;
     m3 = millis() / 500;
     mins = millis() / 1000;
     mins10 = millis() / 10000;
     for (int i =- 75; i < height+75; i++){
       // Reset angle to 0, so waves stack properly
       angle = 0;
       // Increasing frequency causes more gaps
       frequency+=.002;
       for (float j = 0; j < width+75; j++){
         py = i + sin(radians(angle+frameCount*0.1)) * amplitude;
         angle += frequency;
         c =  color(abs(py-i)*m2/amplitude, 255-abs(py-i)*m/amplitude, j*(255.0/(width+50)), m3);
        
         // Hack to fill gaps. Raise value of fillGap if you increase frequency
         for (int filler = 0; filler < fillGap; filler++){
           set(int(j-filler), int(py)-filler, c);
           set(int(j), int(py), c);
           set(int(j+filler), int(py)+filler, c);
     
         }
       }
      
     }
     fill (random(mins), random(mins), random(mins));
     rect(random(mins*10),random(mins*10),mins,mins);
     float xspeed = m;  // Speed of the shape
   float yspeed = m2;  // Speed of the shape
    
    println(mins);
   }
   
   
   

" unreachable code"
After the return line in upDownCounter, the code will no longer be executed, since the return makes the function to exit...

Thanks so much. I'm such a dumbass sometimes. I put the return function at the end of the code so that everything inside executed and so that I could manipulate the code using the counter. At first I couldn't get it to do anything productive at all so I simplified the code so that is was just a static square so that I could change the Red colour using the upDownCounter but even then it's just looping instead of counting backwards.

Upon using println(fcd) I noticed that the numbers were getting to 225 and then looping back to start at zero instead of counting backwards from 225. Any ideas guys?

This is the simplified code.

1. float angle = 0;
   float px = 0, py = 0;
   float amplitude = 30;
   float frequency = 0;
   float fillGap = 2.5;
   int m;
   int m2;
   int m3;
   int mins;
   int mins10;
   color c;
   
   void setup() {
     size(500, 500);
     background(225);
    
    
    
   }
   
   void draw() {
    
    
      int value = upDownCounter(225, 1);
    
   }
   
   int upDownCounter(int maxValue, int factor) {
     int doubleMaxValue = factor*maxValue;
     int fcd = (frameCount/factor)%doubleMaxValue;
    
     fill (fcd, 0, 0);
     rect(50, 50, 50, 50);
     //float xspeed = m;  // Speed of the shape
   //float yspeed = m2;  // Speed of the shape
    
    println(fcd);
    
     return (fcd<225)?fcd:doubleMaxValue-fcd;
    
   }
   

Do not put your code inside the upDownCounter() function! It's a self-contained function that returns a number based on the parameters you enter (using frameCount). Both your println and your code are inside the function before the crucial return line. This is wrong and pointless. For the correct way to use upDownCounter() function, see the code example below.

Code Example

1. int value;
2.  
3. void setup() {
4.   size(1100, 400);
5.   textAlign(CENTER, CENTER);
6.   textSize(100);
7.   noStroke();
8. }
9.  
10. void draw() {
11.   background(255);
12.  
13.   value = upDownCounter(255, 1); // fast
14.   fill (value, 0, 0); // red
15.   rect(50, 50, 300, 300);
16.   fill(255);
17.   text(str(value), 50, 50, 300, 300);
18.  
19.   value = upDownCounter(255, 20); // slow
20.   fill (0, value, 0); // green
21.   rect(400, 50, 300, 300);
22.   fill(255);
23.   text(str(value), 400, 50, 300, 300);
24.  
25.   value = upDownCounter(255, 5); // medium
26.   fill (0, 0, value); // blue
27.   rect(750, 50, 300, 300);
28.   fill(255);
29.   text(str(value), 750, 50, 300, 300);
30. }
31.  
32. int upDownCounter(int maxValue, int factor) {
33.   int doubleMaxValue = 2*maxValue;
34.   int fcd = (frameCount/factor)%doubleMaxValue;
35.   return (fcd<maxValue)?fcd:doubleMaxValue-fcd; // this line is also important!
    
36. }