Requesting exposure of SMP/MVP in dxvk-nvapi

[DanFraserUK]

Hello!

First go at submitting an issue here, hopefully I can explain this well. I am far from technically experienced enough on this subject to go into detail and pick out certain code :(

iRacing is a game that implements SMP/MVP (simultaneous multi-projection, multi view projection - these are a pain to google). It's VR related but the specific purpose in this regard is for the triple monitor functionality, where on top of the functional Render View Mode that wraps the game across angled monitors this SMP/MVP option in iRacing assists with rendering process time with having 3 "cameras"/viewports, very similar to VR rendering.

An announcement (?) link

It would greatly assist with presenting iRacing being functional on Linux!

Looking through the API pages on nvidia.com and https://github.com/NVIDIA/nvapi NV_SMP_ASSIST* is the stuff not in dxvk-nvapi.

I hope you can help!!

[Saancreed]

Hi, considering that this feature looks like something that would have to be done with most of the heavy lifting on DXVK side of things (just like we "expose" Multi Draw Indirect and similar extensions by forwarding the relevant calls to DXVK/vkd3d-proton), I asked Philip and he said that implementing such a thing would be (paraphrasing) a huge pain and a very invasive change that would require months of work just for one or two games to benefit from it, and therefore is not worth the cost.

[sp82]

Hi, I came here to ask the same question for the same reason, iracing! not for linux in particular, even if I am a 25yers linux user i would like to have this for windows and amd gpu just to make AMD gpus looks good! There is alot of hate in the community of iracing regarding AMD and most of them use nvidia gpus because with multi-monitor setup this functionality make a big difference. As developers we know it's not an AMD problem but iracing developers problem that never integrated this extension from AMD, AMD has exposed this functionality via AGS but I already tested dxvk on iracing on windows and works great and vulkan support multiview natively, no need for AGS.
Saancreed are you sure it's require too much work? Vulkan expose already the multiview functionality, can it be used to implement this feature? keep in mind that vulkan was created by the same people that worked this functionality in nvapi in the first place.
I use iracing in VR so no DXVK for me (dxvk guys already expressed their never go to support VR because too much vender extensions to support), so I ask for the people that have AMD gpu with multimonitor. AMD gpus offers more value per dollar and we all need more competition in this space to not allow a monopoly, more choice and value for everyone and more freedom.

[sp82]

I find out that in the specifications of the khronos vulkan multiview extension (https://registry.khronos.org/vulkan/specs/latest/man/html/VK_KHR_multiview.html) linked to the page where nvidia explain nvapi multiview: https://developer.nvidia.com/blog/turing-multi-view-rendering-vrworks
More likely they are 95% identical in implementation.

[Saancreed]

As per my previous comment, there is little-to-nothing dxvk-nvapi can do until DXVK supports this thing. Feel free to file a feature request there, but don't be surprised when the answer is "no". DLSS support is already enough of a headache, so I doubt anyone over there would be willing to add and maintain something as… exotic as this.

[DanFraserUK]

I never had any notification of further messages here, I kind of left this after the (understandably very valid!) response from Saancreed.

However, since my original message I have been reading and reading and reading up on doing this. I have no PR's yet but I'm happy to say I have completed the dxvk-nvapi work for SMP/MVP and soon™ I expect to have dxvk's side done.

I'm not sure if I should ever PR to dxvk-nvapi and dxvk or just rebase on top of newer proton-cachyos's future releases, because of the future maintenance aspect. I'd very much like some guidance on that! The code I can just about manage, the git ecosystem is something that really does not work with my brain lol.

@sp82 Unfortunately, SMP/MVP is an nvidia only. You mention AMD exposing functionality and multiview, have AMD made a NVIDIA Surround equivalent? If that's the tech you mean, that is not the same thing as SMP/MVP.