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Liquid VR

McFaulTech
Explorer
I see the .7/.8 compatibility says sli/crossfire isn't supported. Don't we have to enable crossfire in order to use Liquid VR?
Gigabyte Z97-i5 4670, 8gb 1600mhz G.Skill, crossfired 7970 3gb, EVGA g2 1300 PSU WHERE IS THE VR BASS FISHING???
8 REPLIES 8

cybereality
Grand Champion
I'm not sure about Liquid VR as I haven't used it. However, with Nvidia, only the special VR SLI API is supported. For example a game developer could alter thier game/engine to render with this API. However, just running a normal, non-VR-SLI coded game will result in no performance improvement, and may actually cause compatibility issues like black screens.
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owenwp
Expert Protege
Liquid VR works pretty similarly to Gameworks VR, its a special API that exposes new functionality for multi-GPU rendering that does not exist in Direct3D or OpenGL. Game engines need to implement it themselves, and it requires low level design changes to do so so it will not be automatic. AFAIK that SDK has not been released to the general dev community yet.

McFaulTech
Explorer
as far as I'm reading it doesn't necessarily depend on the ap, but instead on the oculus sdk. This is a quote from AMD and the link which follows is the page the quote originated. look to the very bottom of the link.

"*Oculus SDK 0.7 and later adds Direct Driver Mode, which uses features of AMD LiquidVR to render directly to the HMD. If the installed GPU does not support AMD LiquidVR, it uses Oculus Direct Mode."

http://developer.amd.com/tools-and-sdks ... /liquidvr/
Gigabyte Z97-i5 4670, 8gb 1600mhz G.Skill, crossfired 7970 3gb, EVGA g2 1300 PSU WHERE IS THE VR BASS FISHING???

cybereality
Grand Champion
LiquidVR is a catch-all name for different features that support VR. One such feature is the Direct Driver Mode, which is being used right now by the Oculus runtime and VR applications built with 0.7 or 0.8. There are other planned features, like multi-GPU, which are not available publicly yet and are restricted to specific use-cases as explained in the above posts.
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McFaulTech
Explorer
sooooo confusing! I thought the whole point of liquid vr was to have one gpu render each eye individually to get the max use of two gpu's?
Gigabyte Z97-i5 4670, 8gb 1600mhz G.Skill, crossfired 7970 3gb, EVGA g2 1300 PSU WHERE IS THE VR BASS FISHING???

cybereality
Grand Champion
That is one feature, using multiple GPUs, that may be available in the future.
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owenwp
Expert Protege
The application needs to be coded to work that way. The Oculus SDK has no concept of how the eye images were rendered, it just takes the finished result and puts it on the screen with timewarp. How your geometry gets drawn and on which GPU is something only the engine can decide.

The only reason older SLI/crossfire solutions could be automated is because they do not change anything about how the render pipeline works. All they essentially did was switch between GPUs every frame, so all the render API calls go to one this frame and another the next, and that has the cost of increasing latency by a full frame. Even if the API somehow knew which draw calls and camera state belong to which eye, that approach would leave one GPU idle while it waited for the other to finish. You need both GPUs to get the same draw calls at the same time so they both finish in time to display the frame.

McFaulTech
Explorer
I see what you mean, just that AMD makes it sound like their drivers conform to the oculus sdk and all apps written for the oculus sdk will therefore work. I think it's just sketchy advertising on AMD's part.
Gigabyte Z97-i5 4670, 8gb 1600mhz G.Skill, crossfired 7970 3gb, EVGA g2 1300 PSU WHERE IS THE VR BASS FISHING???