function create(x, y, z) {
  var dst = new VecType(3);

  if (x) {
    dst[0] = x;
  }

  if (y) {
    dst[1] = y;
  }

  if (z) {
    dst[2] = z;
  }

  return dst;
}
Creates a vec3; may be called with x, y, z to set initial values.
@param {number} [x] Initial x value.
@param {number} [y] Initial y value.
@param {number} [z] Initial z value.
@return {module:twgl/v3.Vec3} the created vector
@memberOf module:twgl/v3