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Can you check if your card was on? You should be getting an average of 30 – 35 FPS on these maps. Sometimes if you don’t check the card ON in your profile, it will be turned off when you get into the level. Pain in the ass, I know, but that’s just the way it is set up. It happened to me here in the office as well. I’d really love if you could look at the levels again, if you please. We took major due diligence in developing these maps, and I’m proud of the work we’ve put into them… I truly want to make sure you get the right experience with the hardware on.

–Marti – AGEIA PR Gal

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You can, potentially, run a game like so…

Game Loop #1
Game Loop #2 // Render Results Game Loop #1 // PhysX Results From Conditions At End of #1
Game Loop #3 // Render Results Game Loop #2 // PhysX Results From Conditions At End of Game Loop #2

True, but remember that the player can possibly change the state of the world within that one tick. Consider the following scenario:

a box is pushed towards the player in tick 1
the player moves towards the box in tick 2
the player is in the box in tick 3

The third tick is all wrong because of the lag in physics.

I suspect that the PhysX card could make that single Serial process run faster though

I doubt it. Apart from the overhead of transferring data over the bus AND back (gfx cards only transfer to, not back) the physics card isn’t doing anything a CPU couldn’t do just as well … and the CPU has the added benefit of having direct access to RAM (or at least, faster access).

You’re last point though (about the Twister game) is spot on though. I mentioned this in my original post … the PhysX card works great for debris and special FX, but I imagine would be a bit useless for “proper” gameplay-changing physics.

(apologies in advance for boring the crap out of everyone!)

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In a hypothetical example, lets create a game from the movie Twister. The Twister itself needs to be able to tear the world apart into minute parts and send them flying through the air and into the path of your car. Small incidental things (fence posts, footballs, bricks) just bounce off your car or skit away from the wheels, they serve no game purpose, only act as aesthetic debris. Should the Twister catch up with you, then you see your car get whisked off into the Twister.

None of this impacts the game flow in any way, the renderer runs off the results of the PhysX, the car is just a big block being pushed around by the game telling PhysX to shift it a bit in that direction.

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You can, potentially, run a game like so…

Game Loop #1
Game Loop #2 // Render Results Game Loop #1 // PhysX Results From Conditions At End of #1
Game Loop #3 // Render Results Game Loop #2 // PhysX Results From Conditions At End of Game Loop #2

…and so on. However, you can’t respond to the PhysX results with your Game Loop until one frame after, so there is an inherent delay. It’s far from perfect (and certainly i’d hate working on a game that ran like that) but it is possible.

I suspect that the PhysX card could make that single Serial process run faster though, the PPU using the CPU as additional threads and solving the stuff it can do faster itself… but any moreso than if it ran entirely in software and you spent the money on another dual core? That’s for someone with more hardware and time than me to investigate :P

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I’ve ranted about this far too many times, but I guess there’s no harm in doing it once more …

Physics cards are absolutely useless.

Why? To your everyday gamer, they seem like a great idea … it’ll do to physics what graphics accelerators did to graphics, right? Wrong. There’s a fundamental flaw with the physics card: it isn’t parallel process.

The way graphics accelerators work is as follows: a game updates it’s logic. It then tells the graphics card, “RENDER STUFF!” And away the gfx card goes. While the game is being rendered on the GPU, the CPU is free to go off and start updating the logic again. Graphics and logic are parallel processes. That is, one does not depend on the other.

Physics on the other hand, is *COMPLETELY* dependent on logic and vice versa. When the logic says something like …
if ( gordon hits explosive barrel ) then kill gordon
… it needs to wait for the physics card to finish updating before it can find out the result. Thus any speed gains are given up.

Notice that the only real use you see of the PhysX card is with debris and special FX … you know, stuff the logic of the game doesn’t really care about. That can definitely be made into a parallel process, but anything meaningful to gameplay? Not likely.

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On the other hand, it doesn’t seem like there’s really any purpose for it right at the moment, and it’s priced way too high for something that actually winds up decreasing performance more than increasing it, and only does anything at all in a few games.

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I haven’t heard anything of it for a while, but if they could get that going it would be awesome, a lot of games use havok, and this – it even encourages recycling!

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