TODO

[Sphinxxxx]

• [ ] Bresenham's line algo (https://codepen.io/Sphinxxxx/pen/eYNLzPR)
• [ ] Circles intersection (https://stackoverflow.com/questions/3349125/circle-circle-intersection-points)
• [ ] Lines intersection (https://codepen.io/Sphinxxxx/pen/RwPeRWQ)
• [ ] Line segments intersection? ()https://codepen.io/Sphinxxxx/pen/EZzzOd)

[Sphinxxxx]

Consecutive lines/vectors turn left or right

/*
 * https://algorithmtutor.com/Computational-Geometry/Determining-if-two-consecutive-segments-turn-left-or-right/
 *
 * Returns the cross product of vector p1p3 and p1p2
 *  - If p1p3 is clockwise from p1p2 it returns +ve value
 *  - If p1p3 is anti-clockwise from p1p2 it returns -ve value
 *  - If p1 p2 and p3 are collinear it returns 0
 */
function direction(p1, p2, p3) {
  function subtract(pa, pb) {
    return [pa.x - pb.x, pa.y - pb.y];
  }

  // Calculates the cross product of vector p1 and p2
  // if p1 is clockwise from p2 wrt origin then it returns +ve value
  // if p2 is anti-clockwise from p2 wrt origin then it returns -ve value
  // if p1 p2 and origin are collinear then it returs 0
  function cross_product(pa, pb) {
    return pa[0] * pb[1] - pb[0] * pa[1];
  }

  return  cross_product(subtract(p3, p1), subtract(p2, p1));
}