edit: I was wrong.
Note: a lot of this is basic but for me this was new.
This isn't anything concrete so it's probably full of holes but it just occurred to me that there is a method to prove that Xbox one has some dx12/Maxwell features. I didn't realize this but the ones pushing for voxel global illumination are Nvidia. They've been trying to sell it since 2012 and have had difficulty getting adoption due to the hardware requirements.
To really push it they've made it hardware accelerated and they have been working closely with E4 team. (edit: It was Epic that created SVOGI according to some documentation that I'm reading, a technique that leveraged the work of an Nvidia engineer's thesis. I guess it just makes sense to credit them both.)
From what I understand of VXGI the algorithm can be hardware accelerated with the following: from Anandtech
The forthcoming Direct3D 11.3 features, which will form the basis (but not entirety) of what’s expected to be feature level 11_3, are Rasterizer Ordered Views, Typed UAV Load, Volume Tiled Resources, and Conservative Rasterization. Maxwell 2 will offer full support for these forthcoming features, and of these features the inclusion of volume tiled resources and conservative rasterization is seen as being especially important by NVIDIA, particularly since NVIDIA is building further technologies off of them.
. So VTRs are important to voxel based implementations as is conservative rasterization.
Iike VTR, voxels play a big part here as conservative rasterization can be used to build a voxel. However it also has use cases in more accurate tiling and even collision detection. This feature is technically possible in existing hardware, but the performance of such an implementation would be very low as it’s essentially a workaround for the lack of necessary support in the rasterizers. By implementing conservative rasterization directly in hardware, Maxwell 2 will be able to perform the task far more quickly, which is necessary to make the resulting algorithms built on top of this functionality fast enough to be usable.
It's apparent that there is a very close relationship between Maxwell's feature set, what we find in dx12 and ultimately in Unreal Engine 4.
UE4 supports VXGI, and Fable Legends has fairly great GI then I think it makes sense that it's running VXGI and not some custom Lionhead variant. If we agree to that statement I don't think it's far fetched to believe that XBO has at least the feature set that has been announced already for DX12. Typed UAV, ROV, conservative rasterization and volume tiled resources.
The reason I say this is because in 2012 when nvidia was demoing VXGI at their conference they were only able to get 16 FPS at full HD resolution in a tech demo. That hardware should have been a GeForce 680 at the time IIRC. And that has more juice than the Xbox One.
So I'm thinking with XBO being able to play Fable Legends at 30fps @ 900p there must be some additional assistance in creating that performance. It must contain similar features to maxwell 2.
In this article here
http://blogs.nvidia.com/blog/2014/09/19/maxwell-and-dx12-delivered/ it reads like the dx12 pre-release back in March 2014 of GDC was actually more of ironing out bugs in the API and inefficiencies for games that wanted to target dx12. Not a discussion about feature set. That feature set, that they have been working with nvidia with for such a long time was likely finalized a long time ago.
TLDR; I think XBO has it. Whether it has even more is questionable, but of what they have announced thus far; XBO is capable.
