RO2, SLI, Deffered Rendering and SFR

[mattlach]

Hey all,

I have a quick question for those of you with SLI setups out there or those of you with knowledge of how RO2 rendering works.

I am considering getting a second video card for SLI, but I have some concerns. Default render modes these days for SLI video cards are typically AFR (alternate frame rendering) where one frame is rendered on one GPU and one is rendered on the next. This is done as it has the best compatibility with modern game engines which do a lot of "deferred rendering" and because it scales much better than various SFR (split frame render) modes where the frame is split into multiple parts and both GPU's tackle rendering the same frame before moving on to the next.

While AFR has some clear benefits as regards compatibility and scaling, it also has some real drawbacks. Due to the way AFR works, it inherently introduces so called "input lag" where the players input to the system (keyboard, mouse activity) is delayed before being displayed on the screen.

This is easiest to illustrate with an image taken from an old review of the ATI Rage Fury Maxx, the first video card to use AFR rendering in th elate 90s.



Because of this, I am determined to avoid AFR, and instead use SFR despite it's much reduced scaling.

The question is, if I force it in the driver options, will it work in RO2?

1.) Has anyone tried it? What were your results?

2.) Does anyone know if the implementation of the Unreal 3 Engine that RO2 uses relies on deferred rendering? If it does, forcing SFR likely will not work, in which case I likely won't go to SLI.

I'd rather have a lower framerate than increase my framerate through AFR and wind up with higher input lag.

[mattlach]

Damn, it doesn't allow me to fix my typo in the title

[=GG= Mr Moe]

1) When I had two 8800GTs I tried all the options in SLI and they all worked, but I think I settled on AFR because I had gotten better fps. I don't recall any lag. One card has since died and I replaced it with a GTX560 Ti so I don't remember any more than that.

[clambo]

Originally Posted by =GG= Mr Moe

1) When I had two 8800GTs I tried all the options in SLI and they all worked, but I think I settled on AFR because I had gotten better fps. I don't recall any lag. One card has since died and I replaced it with a GTX560 Ti so I don't remember any more than that.

the 560Ti loves this game

[[TW]redeye]

Originally Posted by mattlach

2.) Does anyone know if the implementation of the Unreal 3 Engine that RO2 uses relies on deferred rendering?

The current rendering pipeline is basically forward rendering with a depth prepass (like deferred rendering). All the dynamic shadows are rendered in a deferred pass, but as far as the actual scene is concerned, it does not use deferred rendering.

[mattlach]

Originally Posted by [TW]redeye

The current rendering pipeline is basically forward rendering with a depth prepass (like deferred rendering). All the dynamic shadows are rendered in a deferred pass, but as far as the actual scene is concerned, it does not use deferred rendering.

Excellent, great to hear it straight form the source.

Have you tested SFR modes at all? Do they tend to work pretty well, or do you wind up with wild texturing geometry problems?

[[TW]redeye]

Originally Posted by mattlach

Have you tested SFR modes at all? Do they tend to work pretty well, or do you wind up with wild texturing geometry problems?

TBH, SLI hasn't received any special attention or testing time. So, at this moment, you'll have to figure out what works best for you. Feel free to share any information from you discoveries, so that it benefits other people as well.

[mattlach]

Originally Posted by [TW]redeye

TBH, SLI hasn't received any special attention or testing time. So, at this moment, you'll have to figure out what works best for you. Feel free to share any information from you discoveries, so that it benefits other people as well.

If I pull the trigger, I will do. Thank you for your input.