Anyone runnin' a PhysX Ageia in their rig? To use, or not to use!

Lupiron

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I havent seen anyone really say a thing about these Physics cards before, so I will ask, I have had one sitting on my shelf for a while, so I decided I may break it out, if they actually do anything!

Feel free to leave your results and comments about the cards if you have one here!

Oh, anyone know where the BFG drivers are for this card? The web site just goes to a blank page when you try and DL from BFGs site!

Thanx in advance!

--Lupi
 

monst0r

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The card was pretty much a failure any way you look at it. Some games might support extra cans or something on the street..it wasn't really implemented well.
 

Lupiron

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Well, I am not worried about scores going up. I am just wondering if they work? No more guy falling on his gun in crysis only to have it poke out his back and make them both jiggle around all crazy because it cant calculate what the physics reactions should be?

Isnt that what they are supposed to stop from happening??

--Lupi
 

Lupiron

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I believe its an option that it is "enabled" if you have a physic card.

Thanks for the drivers!

And well, yeah, they fall and then it does whatever in RL, and they lay there.

In crysis they fall over onto the gun, and just jiggle about for a while. I have had them fall half through the wall onto their weapons and they all just wiggle around until I snatch the gun! Then he slumps down and becomes still.

While the objects are incorrectly interacting with eachother, they do random weird things because of the lack of physics. As in, they just dont know what to do!

My favorite one is still in Halo. I blasted a ghost into a corner and it just kept bouncing around the walls in a circle, because it didnt know that it should loose momentum and apply gravity, lol!

That is what I wanna avoid. The dumb calculation junk.

--Lupi
 

ahmshaegar

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Just so we're clear on this... the physics in games does not have to be good enough to even come close to reality. It only has to look good enough.

If they're using the same equations and models regardless of the hardware, then even if you use a physics card or whatever, you're going to get that weird behavior. End of story.

There is no "lack of physics." It's just that their model is valid for certain things. You come up with that approximate model for games and you know it's not valid for certain things, and you try to design the game and levels such that the player never encounters regions where the physical model used is invalid. Unfortunately, nobody's perfect.

For example, you cited Halo and some kind of bouncing ghost. Something bounced around inside a wall. Why? First thing, what does it mean to be inside a wall? (Sounds stupid, I know... but bear with me.) As far as I know, you can't be inside a wall. Their model probably doesn't govern what happens inside a wall, because you should never be inside a wall to begin with. If you're inside a region of empty space, there's probably a condition where you can move freely inside that space, but the wall is an absolute barrier. Now, if you're inside that wall, it's an absolute barrier.

The physics models for computers are iterative... ex. you have a car with constant acceleration +a in the x direction, initial position 0 and velocity 0. At time t=0, the car is stationary. At time t, which is some short amount of time later, it'll have a velocity (1/2)at^2. At time t + delta t, it'll have (1/2)a(t + delta t)^2. However, in between time t and time t + delta t, it'll have a constant velocity. As delta t gets closer to zero, you perceive a smooth acceleration. If outside forces are involved, they are also evaluated iteratively.

Tying this into the bouncing wall problem, if you run into a wall, you'll bounce back somehow. A lot of games don't even bother to evaluate any kind of collision, because no matter what velocity a dead body hits the wall, they seem to always barely bounce back (so much for "physics") Anyway, you're inside a wall, so you bounce backwards and your velocity is reversed (v changes to -v.) But now, you are still inside a wall, so you hit a wall again, and you bounce back (so -v to v.) If we assume the "collision" they use is just that fudged up model, giving the body some constant v in the opposite direction, you can see this happening forever. For bouncing around in a circle... well, you'll have to ask Bungie what their physical model is.

But anyway, physics in games IS NOT meant to model real physics in any way. It should not, or you'd NEVER get real time gaming.

And remember, physics isn't the real world. The real world is the real world. Physics is how we can quantitatively describe the real world. We do not understand how everything works yet, and perhaps we never will... but we strive to get closer and closer to a "perfect" model. Don't confuse the model for reality with reality itself.

And no, I'm not a physicist. Yet.

Edit: I should clarify that the example I gave was a bad one, since one body at rest with a constant force is a very simple case, and a closed-form solution exists (heck, I used it...) and it's not necessary to solve that problem iteratively. However, a computer is a finite machine, so... A better example to give would be some kind of three body problem, which must be solved iteratively since no closed-form solution exists for the general case. This means that you can't write equations that describe the motion of the three bodies in space and time.
 

Lupiron

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Hmmm, I meant that it kept bouncing around the three walls. Like in a circle. The barrier works, but the way it reacts when it hits it is at fault, then the ghost bounces into another wall/barrier and bounces to the third, which bounces to the first... over and over. because its told to react the same way when hitting the wall, and the walls were at the right angle.. so around and around the ghost went!

The best part? Anyone who walked through the tunnel had to pass the ghost, and if it so much as nicked them, they die! I got to watch a bunch of people get hilled by it!

And my head hurts. I am having enough fun with reading up on PLL, AGTL+ and the refs!! Owwwww!

--Lupi
 

sailer

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A PhysX card won't fix the ghost problem. That's a software bug. The PhysX card was supposed to make explosions look more realistic, with objects bouncing off of each other and going random directions, more like what would happen in real life. Very little software was ever written to take advantage of the card, and more modern cards have largely made it superfluous. If you already have one sitting on a shelf, it won't hurt to install it, but don't expect it to do much of anything, if it does anything at all.
 

pdc76

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i had a physics card for a while in my setup. i realized that while the physics card DOES make things look more realistic, it taxes your video card to DISPLAY those new things. how much, i'm not sure. i guess it depends on how much the game utilizes it. all the extra little things that the physics card allows you to see, must be displayed by your video card, so you may actually see a slight drop in fps, but also see a little extra eye candy. it's really up to you if you prefer quality over speed i guess.
 

Lupiron

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Well that helps, its not out yet, so it would help an 8800 series, and still 9800 series, as they havent announced that they support it.

Thanks for the info!

--Lupi
 

physx7

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+1