What's this "diverse texture" piece of code all about?

finnhusky

float power;
 float d;
 void setup(){
   size(600, 600);
   background(184, 143, 80);
   power = 3;  // turbulence power
   d = 12;   // turbulence density
   noStroke();
   frameRate(3);
 }
void draw(){
  for(int y = 0; y < height; y++){
  for(int x = 0; x < width; x++){
    float total = 0;
    for(float i = d; i >= 1; i = i/2){
      total += noise(x/d, y/d) * d;
    }
    float turbulence = 128 * total / d;
    float base = (x * 0.2) + (y * 0.12);
    float offset = base + (power * turbulence / 256);
    float gray = abs(sin(offset)) * 256;
    stroke(gray, 100);
    point(x, y);
  }
  }
  d++;
  if(d > 128){
    d = 0;
  }
}

I found this on page 132 of "Processing: a handbook for visual designers and artists" and make a little modification to make it "move".

Question is I don't understand the algorithm here. This program generates something like this:

PhiLho

"What's this "diverse texture" piece of code all about?"
It is about making a texture, as you found out as you show an image of the result...

For the algorithm, search the Net about Perlin noise. Starting point: noise()

Alexandros

I am studying the Processing Handbook (2nd edition), and also been stuck in the same example (p. 324, ex. 21_17). So far, every example was comprehensible till this one.

Any hints for where to search for Perlin noise, that does not require too advanced math or another computer language?

Thanks