Source
void setIdentity() {
_data[00] = 1.0; _data[01] = 0.0; _data[02] = 0.0; _data[03] = 0.0;
_data[04] = 0.0; _data[05] = 1.0; _data[06] = 0.0; _data[07] = 0.0;
_data[08] = 0.0; _data[09] = 0.0; _data[10] = 1.0; _data[11] = 0.0;
_data[12] = 0.0; _data[13] = 0.0; _data[14] = 0.0; _data[15] = 1.0;
}