Calculation of hop mesh for thereandbackagain.nz

getHopMesh.js

function getHopMesh(row, toEastingField, toNorthingField, transportMode, material, topHalf) {

  let from = {
    x: eastingToMap(row.data.SA2_usual_residence_easting),
    y: northingToMap(row.data.SA2_usual_residence_northing)
  }
  let to = {
    x: eastingToMap(row.data[toEastingField]),
    y: northingToMap(row.data[toNorthingField])
  }
  let midpoint = {
    x: (from.x + to.x) / 2,
    y: (from.y + to.y) / 2
  }

  let op = to.y - from.y;
  let ad = to.x - from.x;
  let theta = Math.atan2(op , ad);
  let hy = Math.sqrt(Math.pow(op, 2) + Math.pow(ad, 2))
  let radius = hy / 2
  let tubeDiameter = row.data[transportMode] / 5000;
  let arc = (topHalf)? Math.Pi : 2 * Math.Pi;
  let geometry = new Three.TorusGeometry(radius, tubeDiameter, 8, 10, arc);
  geometry.rotateX(Math.PI / 2)

  let mesh = new Three.Mesh(geometry, material);
  mesh.rotateZ(theta)

  mesh.position.x = midpoint.x
  mesh.position.y = midpoint.y
  mesh.position.z = 0;

  return mesh;
}