Killing Floor 2 Demonstrates PhysX Flex Tech Using Guts


Demos for new physics technologies usually look like Bodyform commercials, with gentle blue water sloshing around and lots of smooth rippling fabric. That’s how Nvidia have shown their new unified particle-based physics tech PhysX Flex so far – lots of rubbery water balloons flopping about and leaking blue wet. Pssh, it won’t look like that in the games we actually play.

Killing Floor 2 [official site] will be the first Flex-using game to ship, and a new look at how it uses the tech is more how Bodyform ads should be: scattering gutfuls of fluids, globs, and guts.

As Nvidia explain, current games physics tech tends to run on a load of specialised modules, with separate techniques for rigid bodies, fluids, clothing, destruction and so on. Flex aims to unify all effects, materials and objects under one particle-based physics system, which will let them fully interact with each other. “For example,” Nvidia say, “a water balloon made of rubber can be realistically destroyed by a bullet, the water within can burst out when the bullet strikes, and it can then cause the destroyed balloon to float on its surface.” There’s that blue water again.

With Killing Floor 2, it’s more: a monster made of meat can be unrealistically exploded by a bullet, the blood and guts within can burst out when the bullet strikes, and the blood can then cause the destroyed guts to slip on its surface.

Sadly I can’t embed the images properly here, so go click this and this and this and this for 1080p Gfycat versions.

If you want a ‘grey box, blue water’ demo to help you understand quite what’s happening there, here’s an old demo video from 2014:

In short, guts. Killing Floor 2 is currently on Steam Early Access, where it shall be for a while yet.


  1. king0zymandias says:

    Very impressive, maybe finally they will give Havok a run for their money.

  2. Kitsunin says:

    Oh man, the water in the blobby video looks as refreshing as Super Mario Sunshine’s…I want a platformer with that water in those physics, please.

  3. mukuste says:

    Well, I’m sure it takes a lot of guts to put out something like this.

  4. Cinek says:

    That tech demo looks really amazing. But in the game itself it… it looks decent, but nowhere near as impressive.

    • Razumen says:

      Because it doesn’t have this yet, it’ll come in the next update apparently.

  5. Kollega says:

    Regarding PhysX, the effects sure look nice, but I never quite understood if there’s any point in trying to run them on an ATI graphics card. I tried enabling the PhysX effects in Borderlands 2, and that did result in a substantial hit to performance, but I don’t really have the eye and know-how to evaluate just how optimized or unoptimized they are. Could someone who actually understands this stuff explain to me how much worse PhysX runs on ATI cards as compared to Nvidia cards?

    • gibb3h says:

      Simply put, it DOESN’T run on AMD cards, it is forced to run on the CPU instead.

      Even more annoyingly, even if you bought an nvidia card solely to run Physx on while using your AMD card to run the actual game, it would STILL run on CPU and Nvidia intentionally block it if any AMD cards are detected in the system.

      Ideally Physx would be ported to OpenCL instead of CUDA so that everyone could use it, but that ain’t gonna happen, thanks NV.

      • Kollega says:

        Thanks. I always figured that a proprietary physics engine made by a company selling graphics cards wouldn’t exactly play nice with the graphics cards of their competitors. It’s a good thing that Havok is still the most popular physics engine then, even if it’s not as flashy.

        Then again, maybe Havok not being as flashy is the entire point.

    • TacticalNuclearPenguin says:

      Well, if you enable Physx with ATI in, say, Borderlands 2, you only get:

      1) Reduced Physx effects, only the most basic ones.
      2) No GPU processing whatsoever, only runs on the CPU.

      With Nvidia you get the whole suite of fluid simulation and stuff, and if you try to assign that to the CPU everything explodes. What AMD users do ( or did? ) was fiddling with hacked drivers in order to be able to use a secondary Nvidia GPU alongside their main card without the drivers rudely saying “NO”.

      Not sure if that’s still possible, it’s not a bad thing either since you’re pretty much forced to have a dedicated card which really helps a ton on some titles, rather than having the main one do everything. in this case Arkam Origins with a Titan SLI and a dedicated 650 ran worse than simply disabling SLI and dedicating the other Titan instead.

      Newest cards should be fine though, basically what you need is to find the cheapest card with the highest amount of “cores”.

  6. Skeletor68 says:

    ‘…more how Bodyform ads should be: scattering gutfuls of fluids, globs, and guts.’

    Thank you for that. Unexpected and hilarious.

  7. TacticalNuclearPenguin says:

    Ok then, it’s time for Borderlands 3.

  8. Rumpelstilskin says:

    It’s a good illustration for my thoughts about the whole flex thing. It looks fun in a demos, but it’s hard to find any use for it in a game that’s not a completely gratuitous and unnecessary gimmick. Liquids could have been it, but their particle size is just way to big for it to look like water (or blood) instead of lumps of marmalade.
    That said, portal 2 can probably rebut this entire argument if anyone brings it up.

  9. cakeisalie says:

    I wonder what kind of performance hit it will take to enable these effects? Will you need a second GPU to run the PhysX at a decent frame rate?

    • Xzi says:

      It will probably be a decent performance hit while the game is still in early access, but by the time it releases I’m sure they will have done a lot more optimization work. Typically, PhysX in released games hardly affects performance at all for Nvidia cards. Maybe a drop of 5 FPS, and you’ll almost always have that much to spare. Unless you’re trying to run at 120 FPS or 4K or something.

      I’m probably not the best judge since I have a GTX 970, either. KF2 can’t drop me below 60FPS in V-sync, even with its current lack of optimization.

  10. dozurdogbite says:

    I lllllllllllllllllllllllllike it!

  11. SilentDawn says:

    That akward moment when you own an AMD card :(
    man, AMD users gets screwed everytime. both with CPU’s and GPU’s. well, if you can’t beat them…

    • Razumen says:

      Yeah, I don’t really regret buying my 7970, it’s a great card, but seeing stuff like this is making me want to move it to the HTPC and get a Nvidia card for my main machine.

  12. moms says:

    Alls I know is, I had to turn down “the gore” in KF2 because I couldn’t see a bloody thing, what with guts and shit flying into my face constantly.

  13. Scumbag says:

    link to

    Early look at the GUTS.
    Still think they look a little silly, but KF’s gore is so over the top its almost fitting.