function ceil(out, a) {
  out[0] = Math.ceil(a[0])
  out[1] = Math.ceil(a[1])
  out[2] = Math.ceil(a[2])
  return out
}
Math.ceil the components of a vec3

@param {vec3} out the receiving vector
@param {vec3} a vector to ceil
@returns {vec3} out