code: function convert(fov, fromDimension, toDimension) {
    return 2 * Math.atan(toDimension * Math.tan(fov / 2) / fromDimension);
  }
docs: Convert fov
  
  For example, to convert from hfov to vfov one would call
  `convert(hfov, width, height)`
  
  @param {number} fov
  @param {number} fromDimension
  @param {number} toDimension
  @return {number}
  @memberof util.convertFov