Mirror's Edge PhysX Performance: PPU vs GPU vs CPU February 03, 2009 Brandon Sandman Bell

Mirror’s Edge PhysX Performance: PPU vs CPU vs GPU

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Mirror’s Edge is the first 2009 title to support the technology. Mirror’s Edge also happens to be the first AAA title to support PhysX out-of-the-box: PhysX is an adjustable setting that can be toggled on and off from right within the game’s graphics menu, regardless if you have a GeForce GPU or not. Obviously if you don’t have GeForce 8 or better card installed, PhysX will run on your PCs CPU instead of the GPU. Or if you happen to have an AGEIA PhysX PPU card, you can run Mirror’s Edge on that as well.

PhysX enhancements in Mirror’s Edge

So what enhancements does PhysX bring to Mirror’s Edge? Quite a few. The most obvious addition to the game is persistent shattered glass.

With or without PhysX, glass shatters pretty similarly when it’s hit by bullets. Whether it’s the glass from a window, display case, etc, the effect looks very good. However with PhysX turned off, the glass shatters and literally disappears into thin air, it doesn’t even hit the floor! With PhysX enabled, the shattered glass hits the floor and rests there. It doesn’t disappear after a few moments, and you can even kick up a few shards when you walk over them.

Along the same lines, one other aspect we noticed with PhysX turned on is added objects. For instance, with PhysX enabled, curtains are placed behind many glass windows. When these windows are then shattered, the curtains flop about realistically as the glass basically explodes right in front of it. Occasionally a few of these curtains will pop off completely and fly across the room onto the ground. We’ve taken screenshots of these effects:

[image]

Mirror’s Edge PhysX Impressions

Overall, the added PhysX effects add an additional layer of polish to the game, although we wouldn’t by any means label them as game changers. Unlike PhysX games like Warmonger or Cell Factor, the added physics elements in Mirror’s Edge don’t affect gameplay – for instance there are rumors floating around that shattering glass in Mirror’s Edge with PhysX can cause damage to your character, but those rumors aren’t true. We tested this out by standing right next to a window multiple times as it was shattered and didn’t take any damage.

Basically PhysX brings an additional layer of eye candy to Mirror’s Edge. Nothing more, nothing less. It is however good-looking eye candy that gives the game world an added dose of reality. After all, it’s a bit hard to take a game seriously when an entire wall of windows explodes right in front of your eyes yet leaves no trace of any glass on the floor beneath you.

PhysX basically ensures that the PC version of Mirror’s Edge is the best-looking of all the platforms the game has been released on.

PhysX doesn’t come for free though. You will see a performance hit by turning on this feature. How much of a performance hit bring? Let’s load up some benchmarks!

System setup

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Intel Core i7-965 Extreme Edition

EVGA X58 SLI
3GB Qimonda DDR3-1066

NVIDIA GeForce GTX 260 216 Shaders
NVIDIA GeForce 9800 GTX+
NVIDIA GeForce 8800 GT
NVIDIA GeForce 9600 GT
ForceWare 181.22

ATI Radeon HD 4830 512MB
ATI Radeon HD 4850 512MB
ATI Radeon HD 4870 1GB
Catalyst 9.1

BFG PhysX PPU 128MB PCI
PhysX Pack 8.09.04

300GB Western Digital Caviar SE

Windows Vista Ultimate 64-bit w/Service Pack 1

Benchmarks

Mirror’s Edge with PhysX Patch and maximum graphics settings

Notes

Since Mirror’s Edge lacks a built-in utility for benchmarking, we loaded up FRAPS to record frame rate. Our test sequence comes from checkpoint C of the flight map, and is represented in many of the screenshots from the previous page. At this particular checkpoint a SWAT officer mounted in a Blackhawk helicopter repeatedly fires at you while running through a building. Your character runs out the building, jumps over the edge, and slides down the side to the rooftop of another nearby highrise office building. It’s a pretty action-packed sequence as the chopper is constantly firing on you, sending glass shards everywhere.

Because of this though, there is a little more variability than we traditionally like when testing with FRAPS. Therefore we increased the number of runs to five per resolution, taking the highest figure of the five scores. Ideally we’d prefer something a little more repeatable to ensure consistent results among the various cards, but this is the best method we could come up with given the circumstances.

Also for the sake of completeness, we’ve disabled the 62 fps frame rate cap that Mirror’s Edge loads by default.

First let’s test the performance impact of turning on PhysX…

PhysX On/Off Performance

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In order to test the performance hit of turning on PhysX, we’ve rounded up three relatively affordable GeForce cards running them with PhysX enabled on the GPU, versus turning the feature off completely:

Mirror’s Edge – Direct3D

Mirror's Edge Performance 1920x1200x32
Card	Min FPS	Max FPS
GeForce GTX 260-216 PhysX Off	65	83
GeForce GTX 260-216 PhysX On	38	57
GeForce 9800 GTX+ PhysX Off	49	67
GeForce 9800 GTX+ PhysX On	32	45
GeForce 9800 GT PhysX Off	41	55
GeForce 9800 GT PhysX On	26	35

Notes

As you can see, turning on GPU-based PhysX had a profound impact on performance. The GeForce GTX 260 saw its frame rate drop by nearly half at 1920x1200, falling 40%. The 9800 GTX+ and 8800 GT saw slightly lower hits of 35% and 33% respectively, but the performance drop was still pretty significant. In fact, enabling PhysX has such a large hit on performance, the GTX 260 and 9800 GTX+ perform awfully close to one another at 1600x1200. Only under the greater graphics demand of 1920x1200 does the GTX 260 begin to pull away from the 9800 GTX+.

While these numbers may look rather dramatic, there is a ray of hope. The 38+ fps generated by the 9800 GTX+ and GTX 260 are both what we’d deem playable – even their minimum frame rates remain above 30 fps. So while the performance hit of enabling PhysX is significant, it isn’t bad enough to make the game unplayable in our opinion. For GeForce 8800 GT users may simply want to game at 1600x1200 or turn down the graphics settings a little so you aren’t playing with the game’s highest graphics settings as we are here.

GeForce vs Radeon: PhysX Off

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Mirror’s Edge – Direct3D

Mirror's Edge Performance 1920x1200x32
Card	Min FPS	Max FPS
GeForce GTX 260-216	65	83
GeForce 9800 GTX+	49	67
GeForce 9800 GT	41	55
Radeon 4870 1GB	60	82
Radeon 4850 512MB	42	62
Radeon 4830 512MB	38	53

Notes

Without PhysX enabled, ATI’s Radeon 4800 series takes a backseat to GeForce in Mirror’s Edge. The 4830 lost against its nearest competitor, the 8800 GT, while the 4850 and 4870 were also outperformed by NVIDIA’s equivalent GeForce products, the 9800 GTX+ and GeForce GTX 260. The margins weren’t a complete blowout though. At 1920x1200 the Radeon 4870 and 4830 fell just 5% behind the GTX 260 and 8800 GT respectively, while the 4850 finished 5.5 fps (10%) behind the 9800 GTX+.

Here we should note that CrossFire doesn’t appear to work properly in Mirror’s Edge at this time. As a result, the Radeon 4870 X2 and 4850 X2 perform similarly to their single-GPU counterparts in Mirror’s Edge. Hopefully ATI will issue a hotfix driver to resolve this issue shortly.

CPU vs GPU PhysX

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As you’d expect, running PhysX on the CPU severely hampers performance:

Mirror’s Edge – Direct3D

Notes

In our testing, Mirror’s Edge performance dropped by a factor of roughly 2.5X when PhysX is run on the CPU versus the GPU. As you can imagine, this results in performance that’s completely unplayable, even on a Core i7-965 CPU.

PPU vs GPU vs CPU

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What happened when we plugged in our trusty PCI BFG PhysX PPU card? Despite its age, the PPU performs quite well in Mirror’s Edge:

Mirror’s Edge – Direct3D

Notes

The Radeon 4800 GPUs saw a nice performance boost with the PPU handling PhysX effects, but still can’t catch up to the GeForce GPUs when they’re also paired up with BFG’s PPU card. The Radeon 4870+PPU combo finished behind the GeForce GTX 260+PPU combo by 7%. Meanwhile, the Radeon 4850+PPU setup ran 13% slower than the 9800 GTX+ PPU rig. Fortunately for ATI the margins are slimmer at 1600x1200, where the PhysX effects themselves are more of a bottleneck.

SLI PhysX Performance

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Mirror’s Edge – Direct3D

Mirror's Edge Performance 1920x1200
Card	Min FPS	Max FPS
GeForce GTX 260-216	38	57
GeForce GTX 260-216 SLI	58	79
GeForce GTX 260-216+GeForce 9600 GT	58	77
GeForce GTX 260-216+GeForce 9800 GTX+	59	75
GeForce 9800 GTX+	32	45
GeForce 9800 GTX+ SLI	45	67
GeForce 9800 GTX+ + GeForce 9600 GT	47	62
GeForce 8800/9800 GT	26	35
GeForce 8800/9800 GT+GeForce 9600 GT	38	51

Notes

First off, as we’ve seen in previous PhysX performance articles, the GeForce 9600 GT delivers the best PhysX performance for the dollar among GPUs. PhysX performance was basically on par with the vastly more powerful 9800 GTX+ when both were paired with the GeForce GTX 260 handling graphics.

The two SLI setups we tested, where one card is dedicated 100% to handling graphics, while the second card handles a mixture of PhysX and graphics, ran slightly faster than running the GeForce 9600 GT dedicated solely to PhysX. At 1920x1200 the GeForce GTX 260 SLI configuration outperformed the GTX 260+9600 GT combo by 2%, while the 9800 GTX+ SLI testbed was 5% faster.

Conclusion

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How effective this eye candy is, and whether or not the same or similar effects could also be handled by the CPU (or the GPU using Havok) has been a source of much public debate. Like Ghost Recon: Advanced Warfighter (GRAW), Mirror’s Edge is probably one of those games that could fall into this category.

Now sure, the game looks best when played with PhysX enabled, and there’s no disputing that fact. Going back and forth between PhysX on and off as we did you really get a sense of how stale and boring the game environment is once PhysX is disabled: the game world really comes alive and looks more like a real city with PhysX enabled.

At the same time however, critics will point out that some of the PhysX additions integrated into Mirror’s Edge PC have been handled successfully by the CPU in other PC games in the past: Mirror’s Edge isn’t the first game to feature persistent objects or volumetric smoke/fog. NVIDIA would then likely argue back that previous games didn’t feature physically correct volumetric smoke; the cloth effects with curtains, tarps, and scaffolding that rip realistically in Mirror’s Edge are also impressive.

Basically, Mirror’s Edge is more of an evolutionary progression rather than a revolutionary leap when it comes to in-game physics. Consider it a step in the right direction, but it’s nowhere near the level of a game like Warmonger or Cell Factor.

Looking at the actual benchmarks themselves, NVIDIA’s GeForce GPUs currently have the edge in Mirror’s Edge at this point. Whether you’re gaming with PhysX on or off, and even with an AGEIA PPU card in place, each of the GeForce boards we tested still outperformed their nearest rival from ATI.

Also embarrassing for ATI is the fact that the Radeon 4870 X2 doesn’t scale properly in the game – after spending the past year telling us that their CrossFire scaling performance has improved, they’ve stumbled with the first major PC game release of 2009. This is a major issue ATI needs to address if they wish to restore confidence after the debacle that was the summer of 2007 when many major titles (including BioShock) were released back-to-back without CrossFire profiles.

With F.E.A.R. 2 shipping to stores next week, we’ll be watching closely to see how the 4870 X2 scales with this game.

It will be interesting to see how history judges Mirror’s Edge a few years from now though. Hopefully you saw last week’s review of Mirror’s Edge PC. The game scored a 76% in the review. One of Tom’s biggest gripes was the game’s combat system. After playing the game myself, I completely agree with him. Considering their background with the Battlefield series, DICE’s gun combat implementation in Mirror’s Edge is abysmal. As a result, guns really do play a very minor role in this game. Also, like recent EA Games, Mirror’s Edge features the same draconian SecuROM DRM scheme used in games like Spore and Crysis Warhead.

Four or five years from now, Mirror’s Edge PC will probably be remembered more for issues like these than for PhysX. We wouldn’t be surprised if only the savviest hardware enthusiast remembers that this was the first major game title to ship with built-in PhysX support. That’s both a testament to how smoothly PhysX has been integrated into the game, yet could also be a hindrance when it comes to selling PhysX-compliant hardware. This isn’t a GL Quake moment, where id’s shooter helped 3dfx sell 3D video cards, or a Wing Commander moment, where the game’s voice support helped Creative sell Sound Blaster audio cards.

So here we are, February 2009, still waiting for PhysX’ first killer app…