Beier-Neely

beier-neely.js

// Core math for computing displacement of a pixel per Beier-Neely algorithm:
// http://graphics.cs.cmu.edu/courses/15-463/2004_fall/www/Papers/beier-neely.pdf
function computeDisplacement(p1, q1, p2, q2, x2) {

  const len1 = distanceBetween(p1, q1),
        len2 = distanceBetween(p2, q2),
        u = dot(diff(x2, p2), diff(q2, p2)) / (len2 * len2),
        v = dot(diff(x2, p2), perpendicular(diff(q2, p2))) / len2,
        A = 10,
        B = 1,
        P = 0.1;

  let dist = v,
      weight;

  const x1 = add(
      add(
          p1,
          diff(q1, p1).map(function(d) {
              return d * u;
          })
      ),
      perpendicular(diff(q1, p1)).map(function(d) {
          return d * v / len1;
      })
function computeDisplacement(p1, q1, p2, q2, x2) {

  const len1 = distanceBetween(p1, q1),
        len2 = distanceBetween(p2, q2),
        u = dot(diff(x2, p2), diff(q2, p2)) / (len2 * len2),
        v = dot(diff(x2, p2), perpendicular(diff(q2, p2))) / len2,
        A = 10,
        B = 1,
        P = 0.1;

  let dist = v,
      weight;

  const x1 = add(
    add(
      p1,
      diff(q1, p1).map(function(d) {
        return d * u;
      })
    ),
    perpendicular(diff(q1, p1)).map(function(d) {
      return d * v / len1;
    })
  );

  if (u < 0) {
    dist = distanceBetween(x2, p2);
  } else if (u > 1) {
    dist = distanceBetween(x2, q2);
  }

  return {
    weight: Math.pow(Math.pow(len2, P) / (A + dist), B),
    displacement: diff(x1, x2)
  };

}

function dot(a, b) {
  return a[0] * b[0] + a[1] * b[1];
}

function diff(a, b) {
  return [a[0] - b[0], a[1] - b[1]];
}

function add(a, b) {
  return [a[0] + b[0], a[1] + b[1]];
}

function perpendicular(a) {
  return [-a[1], a[0]];
}

function distanceBetween(a, b) {
  var dx = b[0] - a[0],
      dy = b[1] - a[1];

  return Math.sqrt(dx * dx + dy * dy);
}