Vive SLI Half Frame Rate

hadri

H
I've posted this in the bugs section, but I'll mention it here too. Running ED in VR mode and my frame rate is capped at 45 fps when SLI is engaged making it unplayable in VR. The Vive monitoring bar constantly reports missed frames (lots of red vertical lines). Turning off SLI and everything is fine, but I'm unable to play at the ultra settings my machine should be capable of.

Anyone else seeing this?

Not much discussion on this topic which suggests to me it's either me, or not may people run with SLI lol!
 

imski

imski
If you actually mean SLI (and therefore Nvidia) then yes, SLI isn't supported. However AMD's latest driver does provide a crossfire profile for E: D though I haven't had a time to see if actually works as yet.
 

bitstorm

bitstorm
You would have thought using two cards for VR would be relatively straightforward what with it rendering two display.

Probably not that simple is it?
 

hadri

H
Thanks for the replies guys. ED does support SLI in 2D, I'm just really surprised not in VR, especially with Nvidia's latest drivers spouting "VR optimizations" etc. I'm also surprised AMD are supporting ED and not Nvidia on the multi gpu front, but at least it's reassuring its possible and no doubt forthcoming.
 

daveylad

D
Sworp said:
What card do you have and what graphics settings are you using?
Click to expand...

I'm using 2x GTX970 SC. But obviously with SLI off only using 1 of those. Tried various settings, VR High, VR low both with and without anti aliasing, and 1x supersampling.
 

dementia

dementia
I've not tried the without SLI configuration but I find it very odd that ED works great in SLI with my DK2 and yet not with the Vive?
 

daveylad

D
With the VIve if SLI is turned on you get a terrible stuttering effect with any head movement. Turn SLI off and it disappears. I didn't think there was any SLI support for VR for either the Vive or the Rift.
 

CylonSurfer

CylonSurfer
SLI doesn't work correctly for any of the VR HMDs - DK2, CV1 or VIVE. It used to work fine in builds prior to the Oculus 1.3 update, enabling it now causes stuttering, tacking issues and lowers FPS. 100% not working as intended.
 

Sworp

S
dementia said:
I've not tried the without SLI configuration but I find it very odd that ED works great in SLI with my DK2 and yet not with the Vive?
Click to expand...

DK1/2 used very different tech than the Oculus CV1 or Vive. The DK versions had 1 screen. They basically put Samsung Note 3 panel in there (even with the touchscreen stuff). Check the Ars technica article: http://arstechnica.com/gaming/2014/...-entire-screen-assembly-from-a-galaxy-note-3/

CV1 and Vive have 2 separate panels, one for each eye. I'm guessing that getting SLI/Crossfire to render 2 different panels is somewhat more challenging that doing 1 panel. The graphics manufacturers are working on their SLI implementations. Nvidia has their VRWorks stuff and AMD their liquidsomething. If I've understood it right, the Nvidia VRworks SLI will make each card render one panel only. Instead of the traditional alternating frames per card. That should make the scaling better than the current SLI stuff we've seen, but probably requires support from the game engine as well.

Anyway, I'm not expecting us to see VR SLI support in Elite for a good while.

Edit: This is a pretty good explanation from Nvidia about vr stuffs: https://www.youtube.com/watch?v=09dT3vkwXBA
 
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grammatonfeather

grammatonfeather
hadri said:
I've posted this in the bugs section, but I'll mention it here too. Running ED in VR mode and my frame rate is capped at 45 fps when SLI is engaged making it unplayable in VR. The Vive monitoring bar constantly reports missed frames (lots of red vertical lines). Turning off SLI and everything is fine, but I'm unable to play at the ultra settings my machine should be capable of.

Anyone else seeing this?

Not much discussion on this topic which suggests to me it's either me, or not may people run with SLI lol!
Click to expand...

VR SLI has been incorporated in Nvidia drivers for some time. It's up to developers to utilize it. You should ask Frontier why they aren't supporting it? You should be able to use 1 x GPU per eye.
 

tsh

T
there is some steam stuff on youtube that explains why its not as simple as rendering one eye per card, and getting a doubling of frame rate. Shadows need to be replicated, results need to be merged to one physical port, compositor has to run. Multi-gpu VR needs to be supported in the game engine, it doesnt come for free was my impression...
 

LordZoltan

LordZoltan
tsh said:
there is some steam stuff on youtube that explains why its not as simple as rendering one eye per card, and getting a doubling of frame rate. Shadows need to be replicated, results need to be merged to one physical port, compositor has to run. Multi-gpu VR needs to be supported in the game engine, it doesnt come for free was my impression...
Click to expand...

Multi card VR such as that provided by VR Works and Liquid VR works by sending the same scene to both cards and using different view projections simultaneously. It's slightly more complex than that because you then have view dependent effects, such as reflections, which need to be rendered per-card, but in theory the SDK just handles it if the developer plugs into it.

It's not a 2x perf increase, e.g. the non-connected card also has to send the render result back to the other card to pipe back out the HDMI to the HMD, but it is faster than AFR in traditional Sli.


And yes, it's up to Frontier to support the SDKs.
 
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