let resolution=1;

let step_length = 1;

let numX, numY;

​

function setup() {

  createCanvas(500, 500);

  numX = int(width/resolution);

  numY = int(height/resolution);

​

  for (let i =0; i< numX; i++) {

    // have to create it like this apparently. 

    grid[i]=[];

    for (let j = 0; j<numY; j++) {

      // populating it with random numbers

      //grid[i][j]=random();

      //scaled_x = i * 0.005;

      //scaled_y = j * 0.005;

      scaled_x = i * 0.005;

      scaled_y = j * 0.005;

      // get our noise value, between 0.0 and 1.0

      noise_val = noise(scaled_x, scaled_y);

      // translate the noise value to an angle (betwen 0 and 2 * PI)

      angle = map(noise_val, 0.0, 1.0, 0.0, PI * 2.0);

      grid[i][j] = angle;

    }

  }

  background(255,253,242);

  stroke(0,25);

  //strokeWeight(2);

  // okay now; let's try the curve drawing!

  for (i=0; i<600; i++) {

    //draw_curve(3000,random()*width,random()*height);

    draw_curve(3000,random()*width,random()*height);

  }

}

​

function draw_curve(num_steps, startX, startY) {

  x = startX;

  y = startY;

  print(x,y);

  // basically does a walk where each step in the walk is given

  // by these angles. 

  origcolor = random(255);

  stroke(origcolor,25);

  if (inBox(x,y)) {

    // starting inside the box

    stroke(0,random(120),random(120),25)

  }

  thickness = 1;

  for (let i =0; i<num_steps;i++) {

    // pick a color at random if its inside a box

    // a fun thing to do. 

    //if (x > 100 && x < 200) {

    //  stroke(0,0,random(255),25)

    //}

    angle = grid[gridPoint(x)][gridPoint(y)];

    deltaX = step_length*cos(angle);

    deltaY = step_length*sin(angle);

    //print(x);

    //print(y);

    // have the thickness undergo a random walk. 

    thickness = thickness + random() - 0.5;

    strokeWeight(thickness);

    line(x,y,x+deltaX,y+deltaY);

    //circle(x,y,thickness);

    if (inBox(x+deltaX,y+deltaY) && !inBox(x,y)) {

      // entered box

      stroke(0,random(120),random(120),25);

    }

    if (!inBox(x+deltaX,y+deltaY) && inBox(x,y)) {

      // leaving box

      stroke(origcolor,25);

    }

    x = x+deltaX;

    y = y+deltaY;

  }

}

​

function gridPoint(val) {

  // note this does assume an isotropic grid. 

  return max(0,min(numX-1,int(val/resolution)));

}

function inBox(x,y) {

  if (x > 150 && x < 350 && y > 150 && y < 350) {

    return true;

  }

  else {

    return false;

  }

}

function draw() {

  //line(0,0,100,100);

}