Where's The Physics: The State of Hardware Accelerated Physics
by Ryan Smith on July 25, 2007 4:00 PM EST- Posted in
- GPUs
More than each other however, there's one other thing that threatens the camps offering hardware physics acceleration: the CPU. Recent years have seen CPUs going multi-core, first with two cores and this week has seen the introduction of the (practically) cheap four core Q6600 from Intel. Being embarrassingly parallel in nature, physics simulations aren't just a good match for GPUs/PPUs with their sub-processors, but a logical fit for multi-core CPUs.
While both AMD and Intel have stated that they intend to avoid getting in to a core war as a replacement for the MHZ race, all signs point to a core war taking place for the foreseeable future, with Intel going so far as to experiment on 80-core designs. With the monolithic nature of games these cores will all be put to work in one way or another, and what better way than physics simulations which can be split nicely among cores? While not the floating point power houses that dedicated processors are, with multiple cores CPUs can realistically keep the gap closed well enough to prevent dedicated processors from being viable for consumers. In some ways Havok is already betting on this with their software physics middleware already designed to scale well with additional CPU cores.
Furthermore the CPU manufactures (Intel in particular) have a hefty lead in bringing manufacturing processes to market and can exploit this to further keep the gap closed versus GPUs(80nm at the high end) and the PhysX PPU(130nm). All of this leads to multi-core CPUs being an effective and low-risk way of going about physics instead of a riskier dedicated physics processor. For flagship titles developers may go the extra mile on physics, on most other titles we wouldn't expect such an effort.
So what does all this mean for hardware physics acceleration overall? In spite of the original battle being between the PPU and the GPU, we're wondering just how much longer Ageia's PhysX software/hardware package can hold out before losing the war of attrition, at the risk of becoming marginalized before any decent software library even comes out. Barring a near-miracle, we're ready to write off the PPU as a piece of impressive hardware that provided a technological solution to a problem few people ended up concerned about.
The battle that's shaping up looks to be between the GPU and the CPU, with both sides having the pockets and the manufacturing technology to play for keeps. The CPU is the safe bet for a developer, so it's largely up to NVIDIA to push the GPU as a viable physics solution (AMD has so far not taken a proactive approach with GPU physics outside of Havok FX). We know that the GPU can be a viable solution for second-order physics, but what we're really interested in is first-order physics. So far this remains unproven as far as gaming is concerned, as current GPGPU projects working with physics are all doing so as high performance computing applications that don't use simultaneous graphics rendering.
Without an idea of how well a GPU will perform with simultaneous tasks, it's too early to call to call the victor. At the very least, developers won't wait forever and the GPU camp will need to prove that their respective GPGPU interfaces can provide enough processing power to justify the cost of developing separate physics systems for each GPU line. However given the trend to move things back on to the CPU through projects such as AMD's forthcoming Fusion technology, there's an awful lot in favor of status quo.
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Axion22 - Wednesday, August 1, 2007 - link
Sorry PhysX, you're toast.Multi-core CPUs will have you beat, and by manufacturers who have much more influence in the industry. Even if it did catch on, AMD and Nvidia would just add support and bury you in that market segment.
Aegia would do better trying to get in on the console action. At least there they will have a customer-base.
Zak - Wednesday, August 29, 2007 - link
Yeah, I never liked the idea from the beginning. Count me as one of those who'd rather spend extra $200 on faster CPU than dedicated physics card. What are the chances that many games will use PhysX in a meaningful way, how long PhysX will be around? And, if PhysX is able to run in software mode on one core of a multicore CPU, I'd rather go that way.Z.
0roo0roo - Sunday, July 29, 2007 - link
the simple fact is gamers would rather buy a nicer cpu with more cores with that money. if those cores still can only deliver slightly less physics than the addon, people are willing to live with it. we aren't in a desperate rush to get physics. with the rate at which cpus keep progressing it won't matter, we'll get it regardless. so why worry. its not like sony or nintendo are quaking in their boots at the insane games that physx can create:P the compelling need is not apparent. digital worlds aren't detailed enough for it to matter, people still don't expect things to work in games the same way as reality. physics is limited to blowing stuff up and stacking boxes.and as i said, for online play it won't ever be set for physx cards. if it affects game play than you can't play together with other non physx, so to guarantee compatibility it will be limited to fx and it becomes nothing more than eye candy again.
Bensam123 - Saturday, July 28, 2007 - link
There are quite a few more game available that feature PhysX then just GRAW and GRAW2.http://ageia.com/physx/titles.html">http://ageia.com/physx/titles.html
Not in the list is Rise of Legends. I don't know if it's official, but when installed it installs PhsyX and has quite robust physics in game (ragdolls in a RTS, land deformation, unit movement, etc.).
What I really don't understand and what this article didn't answer, is WHY game developers would pay for a license for a SDK when you can get a better, more user friendly, better supported, more robust, and finely free SDK. It just doesn't make sense to me.
Developers have nothing to lose from using PhysX, but have a lot to gain.
FYI for people that can't read the article, PhysX has a software mode it operates in. The software mode is natively made to run on more then one core. When it all comes down to it, even if you are a advocate for doing physics on a spair core PhysX already does that.
commandar - Friday, July 27, 2007 - link
Wow, this article definitely isn't up to the quality level I generally expect from Anandtech. Typos everywhere and then gems like this:"Being embarrassingly parallel in nature, physics simulations aren't just a good match for GPUs/PPUs with their sub-processors, but a logical fit for multi-core CPUs."
What you say? For one, all processors are not created equal. CPUs are awesome for general purpose work, but a GPU will eat its lunch when it comes to vector math. GPUs are massively parallel vector processors. Physics math generall *is* vector math. While there are problems with doing physics processing which others have already pointed out, suggesting that CPUs are better suited to the job because of parallelism is baffling.
Ryan Smith - Friday, July 27, 2007 - link
Reposted from earlier in the comments:I think you're misinterpreting what I'm saying. GPUs are well suited to embarrassingly parallel applications, however with the core-war now you can put these tasks on a CPU which while not as fast at FP as a GPU/PPU, is quickly catching up thanks to having multiple CPU cores and how easy it is to put embarrassingly parallel tasks on such a CPU. GPUs are still better suited, but CPUs are becoming well enough suited that the GPU advantage is being chipped away.
taterworks - Saturday, July 28, 2007 - link
It's still not parallel enough. A modern CPU has only four cores (the Cell/BE doesn't count since it's not a CPU for PCs), but effective physics processing requires much more parallelism. The Ageia card is better suited to physics processing than any CPU that we'll be able to buy in the next five years. In addition, Ageia identifies a few shortcomings of GPUs when applied to physics calculations. GPUs can't perform read-modify-write operations in their shader units -- they can only perform read operations. In addition, GPUs aren't optimized for applications where each shader unit must execute different code -- they're designed to execute the same code, but on different parts of the image. As a result, some shader units finish their calculations before other shader units and simply sit idle instead of processing the next batch of data. The problem here is that the parallelism advantages become hamstrung by inefficiency. In the end, physics computations are too subtantially different from graphics computations for one optimized processing unit to be applied to a half-hearted form of the other.What's to blame for Ageia's failure? I think there's a fundamental problem with the way gamers think about an immersive gaming experience. Gamers are too preoccupied with resolution, texture and model detail, lighting, and frame rates to notice that objects in games don't behave like real objects. The focus is on visual realism, not physical realism, but both are required for a true virtual reality experience. In addition, the PhysX hardware was too expensive from the start -- it had to be cheaper than GPUs in order for anyone to take a chance on it. A $99 PhysX card was desperately needed last year.
JarredWalton - Sunday, July 29, 2007 - link
Of course, all of what you're saying assumes that we actually need that much physics processing power. I remember reading about a flight simulator a while back where they described all of the complex calculations being done to make the flight model as realistic as possible. After the lengthy description of the surface dynamics calculations and whatever else was involved in making the planes behave realistically, the developer than made the comment that all of that used less than 5% of the CPU power. Most of the remaining CPU time was used for graphics.Granted, that was Flight Unlimited and it was a while ago, but the situation is still pretty similar to what we have today. As complex as physics might be if you model it exactingly, it's really not necessary and the graphics still demand the majority of the CPU power. AI and physics are the other things the CPU handles. People can come up with situations (i.e. Cell Factor) where hardware physics is necessary to maintain acceptable performance. The real question is whether those situations are really necessary in order to deliver a compelling game.
Right now, games continue to be predominantly single core - even the most physics oriented games (Half-Life 2?) don't use multiple cores. And physics calculations aren't really consuming a majority of even one core! Now, give physics two cores that only need to do physics (on a quad core system), and do you see any reason that any current game is going to need a PPU? Especially when the cost of the PPU card is about as much as the cost of a quad core CPU?
I don't, and I don't expect to before AGEIA is pretty much gone. Maybe Intel or AMD will by their intellectual property and incorporate the tech into a future CPU. Short term, I just don't think they're relevant.
0roo0roo - Friday, July 27, 2007 - link
wouldn't they have to create physx only servers if the physics affect gameplay? they certainly aren't going to require physx to play online...i'm guessing it will only be limited to effects for the most part because of this.Bladen - Sunday, July 29, 2007 - link
I'd imagine that hardware physics would not be much more taxing then non-hardware physics, except for RAM, on servers.I'd say that the server would make everyones computer do the number crunching. The server would just say 'player 1 fires a rocket from this position at this angle (and thus hits this wall like so)". Every players individual PhysX card would do its own processing, and calculate to the same answer.
This is purely speculation though, I have no real knowledge of video game programing (or any kind of programming for that matter).