haha. The Direct3d device basically is a huge collection of functions needed to render the graphics you see in games. Halo, like all games, must create an instance of the d3d device and it stores a pointer(address) that points to the list of device functions. Once you have this device pointer, you can hijack/detour these functions. OS does this, but a different method than what I posted above. OS hijacks the entire device before it is even created!