Direct3D feature levels discussion

The separate API version and feature level are quite confusing. It doesn't help that the GPU marketing teams intentionally mix them when it makes their product look better. Every DX API revision has added new GPU features (requiring hardware support). For example 11_1 hardware feature level was included in DirectX 11.1 API. However all the new hardware features in DX 11.2 API (such as tiled resources tier 2) were optional features. Thus there is no 11_2 feature level.

DirectX 11.3 API will bring several new hardware features:
http://wccftech.com/directx-11-3-api/

It will be interesting to see whether all of these are optional features (of 11_1) or whether these form feature level 11_3. Feature level 11_3 would be an odd name, since there is no feature level 11_2. But it would be even more confusing if the new DX 11.3 API hardware features were called feature level 11_2.

 

Ugh I cannot believe Microsoft found a way to make Direct3D even more confusing than OpenGL's extensions. I'm impressed with the speed in which they did it too. Bring back dx10's all or nothing approach! Oh well, I guess this is getting slightly off-topic...

 

As far as i remember it have allways been like that, you have hardware features ( who need specific hardware features for work ), you have some hardware features who can be "emulated" by software ( the optional one ), and some who just need to be included in softwares.. this have permit them to make evolve DirectX features stack without completely break the compatibility with old hardware and without be limited to only hardware change.. ( you cant not support a features on the hardware level, but you can emulated it on the software level ( with a cost on performance )..

Hopefully we have only 3 actors on the gpu PC market. ( intel, AMD, Nvidia )

 

No it wasn't like that in DirectX 10. DirectX 9 had caps which were more or less optional features. But DirectX 10 was truly an all or nothing approach. If a gpu was sm 4.0 or 4.1, you knew exactly what features it supported. No additional queries were required. With DirectX 11 they introduced feature levels/optional features/tiers/etc. that retroactively brought optional features to Direct3D 10 gpus, but there was a window in which DirectX was crystal clear. Now we have IHVs and hardware sites talking about supporting a feature level that doesn't even exist! The whole situation is a complete mess. And unfortunately it looks to be only getting worse.

 

True for DX10.0 , not for DX10.1 .... where only AMD was support the full features on hardware level, when Nvidia was exploit the software way. Im not sure MS is more responsible of this mess than the hardware manufacturer.

 

That was NVAPI (or whatever) and not part of the official DirectX specification. Some nvidia cards were actually Direct3D 10.1 (mostly oem iirc).

 

I don't believe this is correct or at least to the broader point I was making. Direct3D 10.1 didn't introduce new optional features (only new required features), but DirectX 11 retroactively brought optional features to Direct3D 10.x gpus (e.g. compute shaders).

Because I shouldn't have to spend significant amount of time researching what % of gpus currently support y feature (or worse z tier on y feature). For example, there are some obscure optional features today (well last time I checked) that Nvidia supports on Windows 8.x but mysteriously not on Windows 7 (and yes Windows 7 supported those optional features). So it's actually quite difficult to get an accurate picture of who supports what. This "retroactive approach" only adds to the ever growing matrix of what exactly does a feature level 11_x gpu support. Basically I'm unhappy that it creates more fragmentation within a feature level.

 

The point is you seemed to disagree that DirectX 10 was all or nothing. Perhaps I just misunderstood.

While true that doesn't change the fragmentation problem. There are plenty of Windows 7 users that have an otherwise feature level 11_1 capable gpu.

I actually tried editing my post for this (not fast enough ), but the feature was supported in Windows 7.

 

I moved these posts to a new thread since it's not really about broadwell anymore!

 

I actually addressed this rather poorly in the previous post. The problem is not whether or not these features will one day become mandatory, but rather what does the market currently support. These optional features and tiers require further effort and research to determine if they are worth supporting.

 

Then it's my mistake, I thought you were disagreeing with the broader point I was making.

I don't think I'm being clear. I'm talking about something like logical ops which should be supported on Windows 7 with the platform upgrade. When I checked dxcaps on a kepler Windows 7 machine at work (with the platform upgrade) the entry showed up but the feature was unsupported. However at home both my fermi and maxwell cards supported the feature on Windows 8.1. Perhaps it was just a driver quirk, but regardless the original point I was trying to make was this latest trend of retroactively adding optional features has greatly increased confusion about DirectX. I've found in practice it hasn't worked out as well as it should have. I also gave DirectX 10 as an example of something I prefer (all or nothing). I guess if you don't find the current situation confusing, we'll just have to agree to disagree.

Not really related, but Nvidia did release Direct3D 10.1 cards. I assume you don't count this, but maxwell (not the original) is also 11_1.

 

Great point ... In the past it was always the API catching up to what the HW had to offer, but doing it in a way that tried to make it platform/hw agnostic for the millions of windows devs ..


... but now with DX12's low-level-api being sold to us as

1. high-level-API/runtime getting out of the way allowing developers access to the underlying HW
2. Over time if an approach becomes main-stream, it may somehow make it's way back into the a high-level-api to make it easier for the masses of mediocre devs..

It's going to be interesting to see how this pans out