I am not saying that either of those APIs are problem.
About PS5 apis
"Most people start with the GNMX API which wraps around GNM and manages the more esoteric GPU details in a way that's a lot more familiar if you're used to platforms like D3D11. We started with the high-level one but eventually we moved to the low-level API because it suits our uses a little better," says O'Connor, explaining that while GNMX is a lot simpler to work with, it removes much of the custom access to the PS4 GPU, and also incurs a significant CPU hit.
A lot of work was put into the move to the lower-level GNM, and in the process the tech team found out just how much work DirectX does in the background in terms of memory allocation and resource management. Moving to GNM meant that the developers had to take on the burden there themselves, as O'Connor explains:
"The Crew uses a subset of the D3D11 feature-set, so that subset is for the most part easily portable to the PS4 API. But the PS4 is a console not a PC, so a lot of things that are done for you by D3D on PC - you have to do that yourself. It means there's more DIY to do but it gives you a hell of a lot more control over what you can do with the system."
About dx11/12 apis
"The major difference is that with DX12, you need to be very explicit in how you talk to the GPU (via the API). DX11 is a level higher (conceptually), meaning a lot of the heavy lifting is done under the hood (in the driver). You still need to put all the various bits together when using the API (shaders, various states, etc) but you don't really need to think about how all of these things fit together beyond just specifying the thing you need, and setting it.
The explicitness of DX12 involves a lot more work on your part; you need to write a lot more code, track a lot more state (and think about how that all fits together ahead of time), and generally just think through things a lot more carefully. The driver is a relatively thin layer, and most of the heavy lifting is up to the application developer.
With D3D11, the API is much simpler, much less explicit, and so requires much less lift on your part. A ton of work is done (opaquely to you) in the driver. Most modern drivers will spin up a bunch of threads to pull things together into something meaningful for the device, and hide a lot of that overhead.
With DX11, the drivers are heavily optimized, so the performance is pretty darned good. But it still ends up being a lot more work (even if much of it happens "behind the scenes") than a well-written DX12 application where the developer explicitly knows all the parts in the puzzle."
Sounds familiar?
