Half-Life: Alyx was updated this week with an intriguing new feature: a new shader which simulates liquid inside of the game’s many bottles; a small but impressive immersive addition. The update also brought some bug fixes, new subtitle languages, and improved the game’s modding tools.

At launch, Half-Life: Alyx already included a cool immersive detail: many of the game’s small bottles and containers had an associated audio event which—when shaken—makes it sound like there’s actually something inside. Valve took this one step further in the Alyx 1.4 update, which was released this week, by actually rendering liquid inside many of the game’s bottles.

It might seem simple enough—after all, liquid simulations have been around for some time—but Alyx’s approach isn’t really a simulation as that would likely consume too many resources. Instead, the liquid is a shader which is made to look like a convincing simulation.

And it does a pretty darn good job, especially with the way that it interacts with environmental lighting. Valve visual effects developer, Matthew Wilde, said on Twitter that “this booze shader has been my lock-down hobby, required lots of research.”

Image courtesy Phe

The Half-Life: Alyx 1.4 update also added subtitles for eight new languages—Brazilian Portuguese, Czech, Hungarian, Italian, Polish, Portuguese, Ukrainian, Vietnamese—bringing the game’s total subtitle languages to 18.

Valve Explains the Deceptively Simple Design Process That Made 'Half-Life: Alyx' Excellent

The update also added new features, examples, and documentation to the Alyx Workshop modding tools:

  • Enabled the Postprocessing Editor (Documentation)
  • Added “Custom Character” example addon (Documentation)
  • Added example maps for:
    • Blind Zombie (a.k.a. Jeff)
    • Hacking and Toner Puzzles
    • Parked Vehicles and other Interactive Prefabs
    • Visibility System (Documentation)
    • Postprocessing Volumes (Documentation)
  • Added core functionality required for Lua scripting and added some Alyx-specific script bindings for querying VR controller input and creating nav mesh paths from entity scripts
  • Enabled live bone constraints in SFM, which can be baked/enabled as procedural bones, like cloth

The most interesting here is likely “core functionality required for Lua scripting,” which moves the modding tools one step closer to allowing modders to run custom scripts in the game, which should drastically expand the game’s modding possibilities.

The update also made a few bug fixes to the game and the Workshop tools. Check out the full patch notes here for details.

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  • mfx

    Really cool that they keep improving the game like with these little attentions to detail :)

  • starchaser28

    Impressive. I’d love to see them use it in an open tub or pool environment. I’ve been playing around with realistic VR water simulations in Unity and it’s not easy to do: https://www.youtube.com/watch?v=NNYukoRJ_Sg

    • kontis

      Your example is unrelated. Both are fake tricks to approximate liquid, but do completely different things.
      Your video shows even older trick with 2D surface wave propagation and caustics. It wouldn’t work in a bottle and that Valve’s sloshing wouldn’t work in a pool.

      • starchaser28

        They relate in terms of producing realistic liquid/water effects that work in VR. Not all techniques translate to VR. And of course these aren’t true liquid simulations, no one is claiming that.

  • Greyl

    It’s happening!

  • Xron

    Looks almost like real oO

  • Oh WOW! Nothing else to say

  • I just saw this trick on Reddit 2 days ago, and the programmer explained it. It’s not a “Liquid Simulator”. It’s a Z-axis shader with some lag on the plane tilt. The lag gives the appearance of liquid accelerating, so you get the “Slosh”. It looks like they fade in a bubble normal map if the acceleration is high enough. It’s all fun with World-Mapping Coordinates. Instead of using the model’s UV mapping for textures, you use the world’s position. Actual fluid simulations need metaballs in massive numbers. This little trick is far easier and believable enough for a video game.

    According to the programmer who’s post I read, it’s been around for awhile in other forms, as the programmer was using it to show a hand model containing fluid on the Quest. The whole had appeared to be a bottle. As you fired off a spell-attack, the fluid inside the hand would appear to drain away. He called it a “Mana Pool” effect.


    (Oh man, looks like he removed the detailed description of how it works. I should have copied that)

    • CuriousViewer

      Here’s the link. It looks like a very simplified version of Valve’s.

      • mfx

        very simplified then indeed.
        I think that this is quite far in terms of everything.

  • mellott124

    Just saw this. Pretty cool. It’s one of those minor additions that adds to the realism. Also one of those things we’ll take for granted now and expect to see in other games.

  • JesuSaveSouls

    Very interesting in vr