Variable must change from 3.67 to 3.15

p5.js Beginners
1

Hi there!

I need my variable i to go from 3.67 to 3.15 to 3.67 to 3.15 to 3.67 and so on. I’m able to do this just fine from 3.67 to 3.15, however I can’t manage to let it go back to 3.67. This is the code i’m using right now:

  if (i > 3.16) {
    i = i / 1.001
  }
  
  if(i > 3.67) {
    i = i * 1.001
  }

I understand why it’s not working, but I dont know how to fix it. :confused:
pls help

1 Like
2

You can use this:

n = 0.52 - abs(frameCount*0.1 % (2*0.52) - 0.52) + 3.15;

Eh? It’s a function to generate a triangle wave between 0 and 0.52 (the spread of your numbers) with a fixed offset of 3.15; it uses frameCount for the time variable; multiplying this by *0.1 slows down the speed of oscillation to a reasonable amount.

Alternatively,
n = 3.67 - abs(frameCount*0.1 % (2*0.52) - 0.52);

3 Likes
3

Thank you so much!
Clear explanation!

4

If you were trying to this with only introductory primitives (no modulo, no abs()) another way of expressing this idea in code is to set a step value and flip the sign on the step. This is the way that many bouncing ball implementations work

https://processing.org/examples/bounce.html

…only you are bouncing one variable along a single line, rather than in two dimensions x,y.

float step = 0.03;  // or 0.003415 etc
float max = 3.67;
float min = 3.16;
float i = (min+max)/2.0;

void setup() {
  frameRate(4);
}
void draw() {
  i += step;    // move
  if(i>max) {  // high bounce
    i=max;
    step = step * -1;
    println("ping");
  }
  if(i<min) {  // low bounce
    i=min;
    step = step * -1;
    println("pong");
  }
  println(step, i);  // status
}
3 Likes