What fog is viable on mobile devices?

[granite citrus]

I need to implement an URP fog solution but, as I understand it, not many are able to run on old/cheap mobile hardware. Does anyone have any recommendations on what I can use to still have nice looking fog in my 3d enviroments...

The first one I looked at was optimized for mobile and even it said it wouldn't run on old phones : https://assetstore.unity.com/packages/vfx/shaders/fullscreen-camera-effects/atmospheric-height-fog-optimized-fog-for-consoles-mobile-and-vr-143825

This one seems promising : https://assetstore.unity.com/packages/vfx/shaders/fullscreen-camera-effects/dynamic-fog-mist-2-48200

And this one seemed like a quality asset but doesn't talk about mobile performance : https://assetstore.unity.com/packages/vfx/shaders/fullscreen-camera-effects/haze-volumetric-fog-lighting-for-urp-336656#description

Any help would be appreciated it.

[supple isle]

"implement" means you're gonna do it yourself. Not use an asset.
Anyways the cheapest(in performance) you can go for is distance fog, which is included in unity by default.
After that you have height fog. This one basically adds the verticallity factor to distance fog.
Then you have volymetric fog, which is the heaviest and most realistic.

[limber hare]

What kind of environments are they, or rather how / from what perspective are they viewed?
If you want cheap fog, the most important thing is to know how your point of view allows hiding the limitations of the cheap methods
As well as what kind of fog overlap or interactions with lights or other things you need

For example if the view is top-down, that means not having to worry about fog blending with the sky
If the camera never goes close to the ground, a fog plane is easy to do

[granite citrus]

@supple isle : I used the default URP fog and didn't really like how it looked. I believe it is height fog that I am after.

@limber hare : Its going to first person view. I'm still building scene but I can set things up however I want in regards to lighting. I want it it to look good but obviously if it runs badly then I will find a different way (even it if it looks "worse")

[limber hare]

Even with first person view there's a lot of different kinds of scenes, and different requirements for fog
Are there long sightlines or can they be covered up
Is the fog you want more like ground mist, or rainy day fog with low clouds, or something else
An example of the scene you're working with and what kind of fog you want would save us from guessing

[granite citrus]

Here is the scene I'm working on

I want a swamp, that has a magic/purple feel to it.

That current picture is with the URP default fog

I can cover up long sight lines...though I'm not sure exactly how to do that

The fog I want...is similar to what I have...basically a ground cover...but I don't like how it is disappears at the start.

I actually just tried putting a negative number into the start fog parameter and it looks a little closer to what I'm shooting for.

I basically just want a magical / scary swamp...sorry if I'm being vague. I'll take any pointers you can give me. The scene feels to simple/boring right now. I thought better fog would fill it out in a less flat way

I've been trying to get my cat tails to glow purple....not sure if that is possible. They are currently added via Terrian - Details and are just a tga. I'm guessing I have to pull them out of there...add them manually with an material that has emission.

[limber hare]

The most glaring parts are that the skybox has no fog on its horizon, so it doesn't blend with the fogged up objects at all
The water also is piercing through the fog, and seems to be reflecting a different sky altogether

Those two could be fixed rather easily

You probably want some murk on the water surface also to cover up the lack of actual reflections which will also hide that fogs (besides which you have baked into the skybox texture) won't be seen in reflections from shiny surfaces

With fog billboard particles you could add some motion into the fog and visual intrigue into the scene
Silent Hill 2 did a lot with fog particles, as an example

True volumetric fog systems are all pretty expensive to render, and you only tend to need them if you want the fog to interact with light and shadow in an accurate way
Even without that you can use flare billboards to give light sources a foggy glow

If you want the fog to be dynamic or there's more features (like height based fog or light from the directional light) that you want but might not want to spend the time implementing, the first two assets look fine

The third one is unlikely to run on weak mobile hardware
Even if the first two claim to be mobile optimized that's something that's hard to know exactly beforehand and depends on your frame budget
A tailor made solution for your project's needs will be more performant than an asset that has a bunch of extra features, but only if you have the skills to make the custom system performant

[granite citrus]

First off, thank you so much for your time. I can edit the skybox horizon. That makes a ton of sense. The water, is just a plane and I hate it. I spent maybe 5/6 hours trying to get a water shader working and couldn't. I have no idea why but I guess I will jump back into that shortly. Can you give any suggestions on an approach that would look good + reflect the sky etc?

I'm not familiar with the what billboard particals are.

I'm assuming volumetric fog is off the table....I have just an overwhelming amount of things to work on so I'm guessing I'm going to try one of the first two assets I pasted just to see how things change