maths

  o.centerOriginToTopLeft = (x, y, w, h) =>{
    return new THREE.Vector2((w/2)-x, (h/2)-y);
  };

  o.latLonToVector3 = (lat, lng, radius)  => {
    // convert latitude / longitude to angles between 0 and 2*phi
    var phi = (90 - lat) * Math.PI / 180;
    var theta = (180 - lng) * Math.PI / 180;

    // Calculate the xyz coordinate from the angles
    var x = radius * Math.sin(phi) * Math.cos(theta);
    var y = radius * Math.cos(phi);
    var z = radius * Math.sin(phi) * Math.sin(theta);

    return new THREE.Vector3(x,y,z);
    //return new THREE.Vector3(x,y,-z);
  };

  o.xyToLatLon = (x, y, width, height) => {
      // We just linearly convert the image coordinated to the angular latitude and longitude coordinates.
    // Then we center them so the (0,0) coordinate is at the center of the image
    var lat = 90 - 180 * (y / height); // equirectangular projection
    var lon = 360 * (x / width) -180;
    return {
      'lat':lat,
      'lon':lon
    }
  };