let epsilon = 0;

​

function setup() {

  createCanvas(600, 400);

  for (let x = 0; x < width; x++) {

    const xval = map(x, 0, width, 0, 5);

    const yval = exp(-xval) * cos(TWO_PI*xval);

    const y = map(yval, -1, 1, height, 0);

    allPoints.push(createVector(x, y));

  }

}

​

function rdp(startIndex, endIndex, allPoints, rdpPoints) {

  const nextIndex = findFurthest(allPoints, startIndex, endIndex);

  if (nextIndex > 0) {

    if (startIndex != nextIndex) {

      rdp(startIndex, nextIndex, allPoints, rdpPoints);

    }

    rdpPoints.push(allPoints[nextIndex]);

    if (endIndex != nextIndex) {

      rdp(nextIndex, endIndex, allPoints, rdpPoints);

    }

  }

}

​

​

function findFurthest(points, a, b) {

  let recordDistance = -1;

  const start = points[a];

  const end = points[b];

  let furthestIndex = -1;

  for (let i = a+1; i < b; i++) {

    const currentPoint = points[i];

    const d = lineDist(currentPoint, start, end);

    if (d > recordDistance) {

      recordDistance = d; 

      furthestIndex = i;

    }

  }

  if (recordDistance > epsilon) {

    return furthestIndex;

  } else {

    return -1;

  }

}

​

​

function lineDist(c,a,b) {

  const norm = scalarProjection(c, a, b);

  return p5.Vector.dist(c, norm);

}

​

function scalarProjection( p,  a,  b) {

  const ap = p5.Vector.sub(p, a);

  const ab = p5.Vector.sub(b, a);

  ab.normalize(); // Normalize the line

  ab.mult(ap.dot(ab));

  const normalPoint = p5.Vector.add(a, ab);

  return normalPoint;

}

​

​

function draw() {

  background(0);

​

  const rdpPoints = [];

​

  const total = allPoints.length;

  const start = allPoints[0];

  const end = allPoints[total-1];

  rdpPoints.push(start);

  rdp(0, total-1, allPoints, rdpPoints);

  rdpPoints.push(end);

  //console.log(allPoints.size(), rdpPoints.length);

​

  epsilon += 0.01;

  if (epsilon > 100) {

    epsilon = 0; 

  }

​

  //translate(0, -10);

  stroke(255, 0, 255);

  strokeWeight(4);

  noFill();

  beginShape();

  for (let v of allPoints) {

    vertex(v.x, v.y);

  }

  endShape();

  //translate(0, 20);

  stroke(255);

  strokeWeight(2);

  beginShape();

  for (let v of rdpPoints) {

    vertex(v.x, v.y);

  }

  endShape();

  fill(255);

  noStroke();

  textSize(24);

  text("epsilon: " + nf(epsilon,2,2), 20, 25);

  text("n: " + rdpPoints.length, 20, 50);

}