Perlin noise between given points.

rumlac

Hello,

I am trying to figure out a way of drawing a noisy line which must pass through a number of given points. I've been looking at some examples such as (example from Matt Pearson's Generative Art).

void setup() {
  size(500, 100);
  background(255);
  strokeWeight(5);
  smooth();

  stroke(0, 30);
  line(20, 50, 480, 50);

  stroke(20, 50, 70);
  int step = 10;  
  float lastx = -999;
  float lasty = -999;
  float ynoise = random(10);
  float y;
  for (int x = 20 ; x <= 480 ; x += step) {
    y = 10 + noise(ynoise) * 80;
    if (lastx > -999) {
      line(x, y, lastx, lasty);
    }
    lastx = x;
    lasty =y;
    ynoise += 0.1;
  }
}

I am able to set the starting point fairly easily but I can't work out how to get the line to pass through and finish at specific x/y coordinates.

amnon

Perhaps you should mention that this is an example from Matt Pearson's Generative Art.

Look into recursion to break lines that have to follow a path.

PhiLho

First step: parametrize the start and end points.

void setup() {
  size(500, 100);
  background(255);
  strokeWeight(5);
  smooth();

  PVector start = new PVector(20, 50);
  PVector end = new PVector(480, 50);

  stroke(0, 30);
  line(start.x, start.y, end.x, end.y);

  stroke(20, 50, 70);
  int step = 10; 
  float lastx = -999;
  float lasty = -999;
  float ynoise = random(10);
  float y;
  for (float x = start.x; x <= end.x; x += step) {
    y = 10 + noise(ynoise) * 80;
    if (lastx > -999) {
      line(x, y, lastx, lasty);
    }
    lastx = x;
    lasty =y;
    ynoise += 0.1;
  }
}

Then, you can add a slope.

void setup() {
  size(500, 100);
  background(255);
  strokeWeight(5);
  smooth();

  PVector start = new PVector(20, 10);
  PVector end = new PVector(480, 90);

  stroke(0, 30);
  line(start.x, start.y, end.x, end.y);

  stroke(20, 50, 70);
  int step = 10; 
  float lastx = -999;
  float lasty = -999;
  float ynoise = random(10);
  float y;
  for (float x = start.x; x <= end.x; x += step) {
    y = (0.5 - noise(ynoise)) * 80 + lerp(start.y, end.y, x / (end.x - start.x));
    if (lastx > -999) {
      line(x, y, lastx, lasty);
    }
    lastx = x;
    lasty = y;
    ynoise += 0.1;
  }
}

lerp() allows to add an y amount depending on current x position.