code: function floor(out, a) {
    out[0] = Math.floor(a[0]);
    out[1] = Math.floor(a[1]);
    out[2] = Math.floor(a[2]);
    return out;
  }
docs: Math.floor the components of a vec3
  
  @param {vec3} out the receiving vector
  @param {vec3} a vector to floor
  @returns {vec3} out