Copies the rotation matrix from this homogeneous transformation matrix
into rotation.
Source
void copyRotation(Matrix3 rotation) {
final rStorage = rotation._m3storage;
rStorage[0] = _m4storage[0];
rStorage[1] = _m4storage[1];
rStorage[2] = _m4storage[2];
rStorage[3] = _m4storage[4];
rStorage[4] = _m4storage[5];
rStorage[5] = _m4storage[6];
rStorage[6] = _m4storage[8];
rStorage[7] = _m4storage[9];
rStorage[8] = _m4storage[10];
}