code: function add(out, a, b) {
    out[0] = a[0] + b[0];
    out[1] = a[1] + b[1];
    out[2] = a[2] + b[2];
    return out;
  }
docs: Adds two vec3's
  
  @param {vec3} out the receiving vector
  @param {vec3} a the first operand
  @param {vec3} b the second operand
  @returns {vec3} out