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…flowing cloth (flags, tarps) that use PhysX to flow realistically are solid with PhysX off, and block bullets completely. With PhysX on, the cloth can be shot apart and thus shot through.

- from an answer to the question, "What do the levels of Nvidia PhysX do?"

A comment in this answer to this question by @BenBrocka also states:

…the hitboxes are actually different when PhysX are on. Bullets will be stopped by non-PhysX cloth because it's a wall. Bullets cut and then go through PhysX cloth because that's the point, and I do think they will do damage after passing through where the cloth was.

I can confirm that this is true, visually, in a single player game. (I haven't tested this in a co-op game, hence this question.) I've noticed that flowing cloths appear to be rock-solid and bulletproof if playing with an AMD card with PhysX disabled, and that projectiles appear to pass through flowing cloth if playing with an Nvidia card with PhysX enabled. However, if this is not true, i.e. even if projectiles appear to be tearing or passing through flowing cloth with PhysX enabled, they actually aren't, then please feel free to correct me.

If in a co-op game, what if the host has an Nvidia GPU and PhysX is enabled, while the client has an AMD GPU and PhysX is disabled (set to 'low'), and then vice-versa?

What determines whether a projectile can pass through a flowing cloth affected by PhysX (and hit an enemy behind it) - is it the host's or the client's computer? Or does each computer show a different effect for flowing cloths? (Which is weird if in a co-op game.)

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  • But the question you should make here is even though you hit the cloth with an amd with physx disabled or nvidia with physx enabled. Will you still hit the thing behind it? It might look like it doesn't but i'm pretty sure it will both act the same. It is just a visual upgrade not actual gameplay, because why would you program something 2 times.
    – Lyrion
    Apr 25, 2013 at 9:32
  • @Lyrion Do you mean that even if projectiles appear to be tearing or passing through flowing cloth with PhysX enabled, they actually aren't? If you're sure of this, then you could put it as an answer here, or as a comment or answer at this other question. Apr 25, 2013 at 10:07
  • No what i'm saying is either they pass through the cloth (physx enabled or disabled) or they get blocked when they hit the cloth (physx enabled or disabled). The only difference is the way it looks.
    – Lyrion
    Apr 25, 2013 at 11:10
  • @Lyrion I edited my question, to try to sound something like what you're trying to say. I initially assumed that PhysX enabled -> flowing cloths will not block bullets, and PhysX disabled -> flowing cloths will block bullets, based on the answers and comments I quoted, and from what it appeared to be. I edited my question to not sound like it assumes that those were true. Apr 25, 2013 at 11:36

2 Answers 2

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Just tested it. There's a string of flags right above the Ammo Vendor in Southern Shelf, very convenient.

Indeed, PhysX setting changes the hitboxes of objects - some non-simulated cloth stops bullets, while the same simulated cloth is not in the same place at all, and stops some bullets elsewhere.

The answer is: each computer determines bullet collision on its own, then sends the bullet path to other players. That is:

  • you always see your bullets conform to your PhysX setting,
  • other players see your bullets stop in mid-air / go through seemingly bulletproof flags.

Science!

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  • Hooray for science! Thanks! This is what I would like to know. Apr 29, 2013 at 3:32
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    But....do they actually hit things on the other side? As in cause damage/healing (with the Siren skill for that)? That seems to be the main thing in need of testing
    – Ben Brocka
    Apr 29, 2013 at 12:11
  • @BenBrocka This seems to depend on the bullet type and/or cloth type. A large flag on a pole (absent without PhysX) had not stopped bullets from Slagga - bullets just tore through cloth. A flag string mentioned above was pretty hard to hit with regular bullets, so I switched to Torgue - and it blocked gyrojets (and got ripped to shreds).
    – Orc JMR
    Apr 29, 2013 at 13:55
  • @OrcJMR yes, on first hit they'll block bullets, but after the fabric is torn you can shoot through what is a solid wall on other people's games. What I think would be interesting to know is whether shooting through where cloth was is actually able to hit things
    – Ben Brocka
    Apr 29, 2013 at 16:43
  • @BenBrocka This would require some hassle to test, but I'm sure hitting enemies follows what I deduced just as well - a local PC computes bullet path and a hit, and sends it to other clients. Wouldn't make sense to implement bullet pathing in one way and bullet stopping condition in another.
    – Orc JMR
    May 1, 2013 at 14:43
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PhysX effects are based solely on your local PC; other players don't see the flowing cloth/etc that you do if they have PhysX off. If you both have PhysX on I'm not even sure if their bullets cut the fabric on your game or not, however. But the solid/permeable nature of the cloth is set only based on your local PC's PhysX setting, the host's setup doesn't affect you at all (after all, forcing PhysX on people without Nvidia PhysX-enabled cards could introduce a significant amount of CPU usage only for minor cosmetic effects).

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  • "other players don't see the flowing cloth/etc that you do if they have PhysX off. If you both have PhysX on I'm not even sure if their bullets cut the fabric on your game..." I've seen the same cloth (not in the same co-op game though), in Liar's Berg, on an AMD card with PhysX disabled, and on an Nvidia card with PhysX enabled. The same cloth was bulletproof on the former, but can be hit and reacts to bullet hit effects on the latter. Apr 24, 2013 at 12:57
  • The bullet effects are also handled by PhysX and are just aesthetic, the hit detection works the same in both instances and is not handled by PhysX
    – kalina
    Apr 24, 2013 at 13:01
  • @galacticninja yes, some cloth is present when PhysX is disabled, but as I note in my other answer, it's solid and can't be deformed. If one player deforms the cloth on PhysX and you don't have PhysX you won't see the deformed cloth (it would require PhysX after all)
    – Ben Brocka
    Apr 24, 2013 at 13:07
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    @kalina So bullets don't actually pass through flowing cloths (and can't hit enemies behind it) even if PhysX is enabled? (Are all flowing cloths actually solid and bulletproof even with PhysX enabled?) Apr 24, 2013 at 13:44
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    Not quite; the hitboxes are actually different when PhysX are on. Bullets will be stopped by non-PhysX cloth because it's a wall. Bullets cut and then go through PhysX cloth because that's the point, and I do think they will do damage after passing through where the cloth was. So it's technically a gameplay difference, it's just irrelevant in 99.9% of cases. Cloth will almost never block your shot
    – Ben Brocka
    Apr 24, 2013 at 13:50

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