​

const GRAB_RADIUS = 5;

let grabVector;

​

function setup() {

  createCanvas(400, 400);

  noFill();

  t = new Tri(50, 50, 350, 50, 200, 300);

}

​

function draw() {

  background(220);

  t.draw();

}

​

function mousePressed() {

  grabVector = t.getGrabVector(mouseX, mouseY);

}

​

function mouseDragged() {

  if(grabVector) {

    grabVector.x = mouseX;

    grabVector.y = mouseY;

  }

}

​

function mouseReleased() {

  grabVector = null;

}

​

class Tri {

  constructor(ax, ay, bx, by, cx, cy) {

    this.a = createVector(ax, ay);

    this.b = createVector(bx, by);

    this.c = createVector(cx, cy);

  }

  getGrabVector(x, y) {

    let p = createVector(x, y);

    if(inGrabRadius(this.a, p)) {

      return this.a;

    }

    if(inGrabRadius(this.b, p)) {

      return this.b;

    }

    if(inGrabRadius(this.c, p)) {

      return this.c;

    }

    return null;

  }

  //x = (x1 sin 2A + x2 sin 2B + x3 sin 2C)/ (sin 2A + sin 2B + sin 2C)

  //y = (y1 sin 2A + y2 sin 2B + y3 sin 2C)/ (sin 2A + sin 2B + sin 2C)

  //r = abc/sqrt(a+b+c)(b+c−a)(c+a−b)(a+b−c)

  circumCircle() {

    let ab = p5.Vector.sub(this.a, this.b);

    let ac = p5.Vector.sub(this.a, this.c);

    let ba = p5.Vector.sub(this.b, this.a);

    let bc = p5.Vector.sub(this.b, this.c);

    let ca = p5.Vector.sub(this.c, this.a);

    let cb = p5.Vector.sub(this.c, this.b);

    let A = ab.angleBetween(ac);

    let B = bc.angleBetween(ba);

    let C = ca.angleBetween(cb);

    let div = sin(2 * A) + sin(2 * B) + sin(2 * C);

    let x = (this.a.x * sin(2*A) + this.b.x * sin(2*B) + this.c.x * sin(2*C))/div;

    let y = (this.a.y * sin(2*A) + this.b.y * sin(2*B) + this.c.y * sin(2*C))/div;

    let la = ab.mag();

    let lb = bc.mag();

    let lc = ca.mag();

    let r = (la*lb*lc)/sqrt((la+lb+lc)*(lb+lc-la)*(lc+la-lb)*(la+lb-lc));

    return createVector(x, y, r);

  }

  draw() {

    triangle(this.a.x, this.a.y, this.b.x, this.b.y, this.c.x, this.c.y);

    circle(this.a.x, this.a.y, GRAB_RADIUS * 2);

    circle(this.b.x, this.b.y, GRAB_RADIUS * 2);

    circle(this.c.x, this.c.y, GRAB_RADIUS * 2);

    let circ = this.circumCircle();

    circle(circ.x, circ.y, circ.z * 2);

    circle(circ.x, circ.y, GRAB_RADIUS * 2);

  }

}

​

function inGrabRadius(v1, v2) {

  return v1.dist(v2) <= GRAB_RADIUS;

}

​

​