trip.three/lib/util/worldPositionToPlane.js

Three.js addon for Trip

'use strict';

var THREE = require('three');

var rayFromWorldAndCamera = require('./rayFromWorldAndCamera');

module.exports = function (worldPos, origin, normal, camera) {
  var ray = rayFromWorldAndCamera(worldPos, camera);

  // http://en.wikipedia.org/wiki/Line-plane_intersection
  var p0 = origin;
  var l0 = ray.origin;
  var l = ray.direction;
  var n = normal;

  var num = new THREE.Vector3().subVectors(p0, l0).dot(n);
  var den = l.dot(n);
  if (Math.abs(num) < 1e-6) {
    // In plane
    return worldPos.clone();
  } else if (Math.abs(den) < 1e-6) {
    return undefined;
  } else {
    var d = num / den;
    return new THREE.Vector3().addVectors(l0, l.clone().multiplyScalar(d));
  }
};