segseg/segpoint.js

2d segment to segment intersection detection

// from https://gist.github.com/mattdesl/47412d930dcd8cd765c871a65532ffac

function sqr (x) {
  return x * x
}


function dist2 (v, w) {
  return sqr(v[0] - w[0]) + sqr(v[1] - w[1])
}


// p - point
// v - start point of segment
// w - end point of segment
function distToSegmentSquared (p, v, w) {
  const l2 = dist2(v, w)
  if (l2 === 0)
      return dist2(p, v)

  let t = ((p[0] - v[0]) * (w[0] - v[0]) + (p[1] - v[1]) * (w[1] - v[1])) / l2
  t = Math.max(0, Math.min(1, t))
  return dist2(p, [ v[0] + t * (w[0] - v[0]), v[1] + t * (w[1] - v[1]) ])
}


// p - point
// t0 - start point of segment
// t1 - end point of segment
// return boolean indicating if p is on the segment
export default function distToSegment (p, t0, t1) {
  return Math.sqrt(distToSegmentSquared(p, t0, t1)) < 1
}