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Old June 14, 2010, 08:20 PM
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Default PhysX Question! How does it scale....

So, ongoing research into PhysX and adding it to my system has cropped up a few questions in my mind. Namely the following:

1 - When using PhysX on a system with a 22'' screen vs a 30'', assuming the GPU performance stays constant (I.E. not bogged down by the added pixels) will the PhysX performance decrease? I'm curious now whether or not a 9800GT, for example, will provide the same framerate at low resolution as it would on my Eyefinity setup.

2 - When running Eyefinity + PhysX, will the added aspect ratio also cause a hit in performance? Higher aspect ratio + a greater FOV means there will be more of the game and its surrounding that may have physx effects happening at any time....

What do you guys think?

It's a "tuffy" as headsh0t would say
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Old June 14, 2010, 08:34 PM
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same resolution=same fps on different monitors, unless someone says otherwise
2-hmm....no idea...but the more you cram the slower it will be, thats normal

bottom line if you look tru the posts in the other threads a gtx 260 gives massive improvements as a standalone physx card to the ati unit, i think double the framerate in some cases.
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Old June 14, 2010, 08:39 PM
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haha oh yes it's quite the tuffy. What I'm not sure of though is if it can't be seen on screen but there are still physx effects that are taking place, does the GPU still calculate that information? Watching the comparison video of Metro 2033 you can see that the extra chunks of wall or icicles, etc stay on the ground as extra objects. So will the GPU still be calculating(not rendering) all that stuff going on that would not be on screen on a smaller resolution/aspect ratio? I think if that question can be answered then, you'll be able to tell if performance will take a hit at higher aspect ratio's and resolutions.
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Old June 14, 2010, 09:01 PM
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well, look at it practically. you have a 'world' that you play in. when you turn, the stuff that was in the background becomes 'primary' since you see it on the screen. if there was nothing done, youd probably dip fps wise till it picks it up

that or im wrong :D
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Old June 14, 2010, 09:36 PM
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PhysX deals with physical interactions, not with rendering. I would think that PhysX performance doesn't depend on the number of objects in view since calculations would need to be performed for all objects in the area regardless of whether or not they are visible.
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Old June 14, 2010, 10:24 PM
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Quote:
Originally Posted by Zero82z View Post
PhysX deals with physical interactions, not with rendering. I would think that PhysX performance doesn't depend on the number of objects in view since calculations would need to be performed for all objects in the area regardless of whether or not they are visible.
That's exactly what I am thinking.

Even if a box or whatever object falling behind you for example is not in your fov, in theory that shouldn't affect at all the frame rate or overall performance since the motion/physic of the object has to be calculated anyway. (minus the performance hit from rendering the object if it had to be rendered if it was in front of you).
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Old June 15, 2010, 02:25 AM
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1) I would assume not, PhysX is mainly mathametical calculations to traject realistic motions for particles. As long as its only a resolution increase with no FOV change you would presume that because theres the same amount of objects being rendered, there would be the same amount of necessary PhysX calculations. No additional calculations would imply identical PhysX performance. Or at least theretically it would ;)
2) A greater field of view would suggest more objects in visibility and hence more calculations to determine respective trajectories. As Zero82z pointed out though, they might be rendered regardless of whether their in vision or not. I guess it just depends on how the games been developed.


DISCLAIMER: ALL THAT IS THEORETICAL AND JUST HOW I REASON THINGS TO WORK, THEREFORE, ITS PROBABLY ALL WRONG :P That and apologies for the bold writing half way, something funky went wrong whilst i was writing this comment :S
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Old June 15, 2010, 06:16 AM
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This is all speculation though, does anyone actually know? Why would phyics be needed to keep track of things that aren't on the screen? For all we know, the cpu/engine may take care of such things when the physx object(s) is/are not in view. I WILL find out though, one way or another
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Old June 15, 2010, 08:58 AM
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Quote:
Originally Posted by CMetaphor View Post
Why would phyics be needed to keep track of things that aren't on the screen?
Because they still exist and they still have interactions with the environment.
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Old June 15, 2010, 04:44 PM
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Zero is correct. It does not matter if you are not looking at it and across the map. It still has to calculate everything. Just because you look away does not change that physics are still happening all around. Think of it this way. If A.I. was only calculated when looking at it it would not shoot at you when you turn your back making the game lame. (I know lame example).

(a better example)
Think of an avalanche going on in the distance. You then turn around. Would it be realistic if the avalanche paused till you turned around and looked at it?


Physx has nothing to do with rendering and all about calculations and a whole lot of it.
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