code: function identity(out) {
    out[0] = 1;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 1;
    out[5] = 0;
    out[6] = 0;
    out[7] = 0;
    out[8] = 1;
    return out;
  }
docs: Set a mat3 to the identity matrix
  
  @param {mat3} out the receiving matrix
  @returns {mat3} out