Feedback Volumetric Clouds

So with the latest release of HDRP 12 we finally got volumetric clouds and they look quite good so far.

You have plenty of options to customize the clouds and the lighting looks correct, especially in combination with the PBSky (the other cloud option "Cloud Layer" doesn't, but that's another story).

The only major drawback is the way how cloud shadows are handled.
It just uses a light cookie on the directional light, which works fine if every object/surface is below the clouds, but as soon as something is above them it looks wrong ofc.

It also seems that the clouds only support one directional light at a time. I use two (sun+moon) and I have to turn off the sunlight to make the moon effect them, however this might be just a bug.

 

My feedback is, cloud layers are too thin, for example red dead redemption 2 has multiple layers and looks a lot more believable and realistic. Being able to add thicker layers/more layers with different noise patterns would be great!

 

Well, you can...
Using the manual mode gives you all the control you need, it's just about designing your lookup textures and tweaking the parameters.

 

I would love to see good translucent shadows in the future for stuff like volumetrics and particles(also dreaming about something like volumetric output for shader graph)

 

nice!

yeah then, I would say better presets that would allow us to get these types of results w/o going into the manual design process would be much appreciated.

 

Yeah this would be really helpful as right now it sometimes gets a bit confusing when handling day-night cycles

 

Is this available in the latest alpha (a9) or did you use the GitHub repo?

 

Also, it will be helpful if the game object could cast shadows on the cloud as I'm imagining it to be the case for some sort of stylized high rise building or mountains maybe

 

Yea it's in the latest alpha.

 

For some reason they are not rendered for me, I enabled them in volume and render settings but I'm not seeing any changes when I enable them nor I have an option to select them in the clouds option of the visual environment

 

Yeah I forgot about the default settings, Thanks

 

There's a great video showcasing the RDR2 volumetric clouds here. Would love to be able to fly through and above them using HDRP volumetric clouds, even if this means extra performance cost. (starting at 2:30)

 

Hah, if that's the case then I have some idea what's going on.
I don't have any graphics/master branch running here. Is there currently any functionality for (slowly) transitioning between these presets at runtime? I'm looking forward to the Unite Now video.

 

Would really love to get some insights into how they pull off these tricks

 

I know that only one directional light is supposed to cast shadows and that's totally fine, but I need both the sun and moon light to have the PBSky properly simulated, especially at dawn/dusk.
And suddenly turning off the sun when the moon appears isn't a good solution in this case.
So atleast make it pick the real "sun" (which is the shadow casting light) automatically.

I'd like to use both solutions together, but unfortunately they use inconsistent lighting.
The cloud layer has a very different and simplistic lighting model and obviously doesn't match the lighting of the volumetric clouds, so it's impossible to use both in combination.

 

Btw it would be really helpful if some of the settings like cloud offset are available in the simple mode as well

 

Would be lovely to get some artist tuned samples for volumetric clouds too to get better impression what all we could achieve with this visually.

 

I found some bugs in this version of volumetric clouds where they just seem to flicker a lot like the temporal accumulation is completely disabled and are hardly visible at all, also towards the end you can see it doesn't really look natural how it fades into the fog when going below the ground plane

 

I really don't know how to reproduce this issue as I can't figure out a particular reason or a way to reproduce it
It is hit and miss kind of bug

 

You need a more correct basis and the problem gets a lot easier. Switching on a moon light when you switch off the sun light is wrong and is just creating unnecessary problems. Base it all on luminance. It's a relatively small amount of additional work for a much improved outcome.

So you have body luminance, ambient luminance, and then DL's are simply a thing that a dominant body gets in a specific luminance range. What you will end up with in a sun/moon scenario is a fairly large gap where there is no DL on at all. The ambient light will be dominant.

Directional lights are really an engine construct for performance reasons. So it's easy to conflate things here that really shouldn't be.

 

Not sure what you are referring to, but the entire rendering (and the ambient light ofc) of the PBSky depends on the directional lights as they are the only source of light (except the sky emission texture). So you cant just turn them off or arbitrary manipulate them, because it would just break the sky rendering in an unrealistic manner.

 

I did all of this, and still don't see any clouds, only shadows from them on the ground.

 

Try increasing the far plane to something like 10km or 50 km

 

I'm sorry for mentioning other engines, but I'm really curious -- if anyone has experience with both volumetric clouds in Unity & Unreal, how does unity's VC perform?

If no one has experience with both, I'll check it out soon when I got time

 

Last I checked Unreal's cloud do look better at default settings(didn't really know much as to how to customize them much, so can't go much into details) but somehow the performance was much worse for me, Unity's volumetric cloud does seem like a nice compromise between performance and quality, they look pretty good for in 90% of the situations(i.e, for when you are not above them or inside them) and if Unity provide a better shading and shadowing model in the future for those who need it, I don't think there's anything we are missing out on

 

All this at around 190 FPS for me

 

It's not helping, no clouds. What a hell?

 

Could you share the settings for this, I haven't been able to get something like this

 

Are the volumetric clouds coming to URP at any point (for compute capable devices)?

 

Well I'm still experimenting with this too and I'm slowly getting appealing results.
In case you just want to know how to author the textures, then read the related documentation.
https://github.com/Unity-Technologi...ic-Clouds.md#cloud-map-and-cloud-lookup-table
I'm using substance designer to create them.
You can find the textures(just the LUT though) for the preset clouds in ..."YourProjectName"\Library\PackageCache\com.unity.render-pipelines.high-definition@12.0.0\Runtime\RenderPipelineResources\Texture\VolumetricClouds

I noticed that the lighting (using the PBSky) of the clouds isn't effected by the actual position of the sample points in world space, so I looked at the clouds shader code and found out that the lighting is always sampled at origin (0,0,0) and not where the clouds actually are.
Will this be fixed in a later version or atleast add an option for it?
Because I'd like to have proper physical lighting especially at higher cloud altitudes at dawn/dusk (it currently behaves like the earth is flat).

Another question;
Will there be some sort of point light support for the clouds, in case someone wants to simulate thunderstorms with lightning?

 

I should have made it clearer...
I was primarily referring to the directional light behaviour, not the ambient light.
The ambient light doesn't change much anyway, but the directional light does.
On a low sun altitude the lower clouds can be lit with a red-orange light while the upper clouds are still yellowish-white, but currently they are all lit uniformly regardless of their height/position.

As I said earlier this is due to the fact that the lighting is always sampled at world origin "float3 X = float3(0.0, 0.0, 0.0);" in this specific function.

Code (CSharp):

1. EnvironmentLighting EvaluateEnvironmentLighting(CloudRay ray)
2. {
3.     // Sun parameters
4.     EnvironmentLighting environmentLight;
5.     environmentLight.sunDirection = _SunDirection.xyz;
6.     environmentLight.sunColor = _SunLightColor.xyz * (_ExposureSunColor ? GetCurrentExposureMultiplier() : 1.0);
7.     environmentLight.ambientTerm = SampleSH9(_AmbientProbeCoeffs, ray.direction) * GetCurrentExposureMultiplier();
8.  
9. #ifdef PHYSICALLY_BASED_SUN
10.     if(_PhysicallyBasedSun == 1)
11.     // TODO: move this into a shared function
12.     {
13.         float3 X = float3(0.0, 0.0, 0.0);
14.         float3 C = _PlanetCenterPosition.xyz;
15.  
16.         float r        = distance(X, C);
17.         float cosHoriz = ComputeCosineOfHorizonAngle(r);
18.         float cosTheta = dot(X - C, environmentLight.sunDirection) * rcp(r); // Normalize
19.  
20.         if (cosTheta >= cosHoriz) // Above horizon
21.         {
22.             float3 oDepth = ComputeAtmosphericOpticalDepth(r, cosTheta, true);
23.             // Cannot do this once for both the sky and the fog because the sky may be desaturated. :-(
24.             float3 transm  = TransmittanceFromOpticalDepth(oDepth);
25.             float3 opacity = 1 - transm;
26.             environmentLight.sunColor.rgb *= 1 - (Desaturate(opacity, _AlphaSaturation) * _AlphaMultiplier);
27.         }
28.         else
29.         {
30.             // return 0; // Kill the light. This generates a warning, so can't early out. :-(
31.            environmentLight.sunColor = 0;
32.         }
33.     }
34. #endif
35.     return environmentLight;
36. }
37.  

 

In unreal, they have a workflow to paint the clouds in-engine, something really nice to have in unity as well
I remember someone had a custom open-source system for unity that also had these features
https://github.com/kode80/kode80CloudsUnity3D

Unity could implement something similar
It also has a cubemap generator but I guess we could just bake a cubemap using reflection probes ourselves.

Sorry to compare it with unreal, but I'm just curious if we will ever get clouds that match this kind of quality?



Because right now although they are functioning and are good enough for many cases, their shading is still not on par with what you see here, and considering that I am just a gameplay programmer I don't think I'll be able to modify the default system to such an extent(the default LUT, etc), nor do I have a Big team(anyone else actually ) that could help with this,(my point being that most users will stick to the default settings and modify them a bit instead of making complete new maps)

 

Also, I'm trying to make something like (without the shadow part right now) but haven't been able to do it, It would be really helpful if could include an example for this kind of situation.
When I modify the PBS Sky to have such a small radius(4km) it just starts glitching out, and on actual earth like scale it hardly is feasible to make some like this, considering unity doesn't support 64-bit precision(I tested it but didn't work for me, started having a lot of rendering bugs when zoomed out


I have also placed a sphere of the same size(8000 scale) at the center of the planet, and volumetric fog doesn't support this kind of setUp(spherical planet like fog) by default so, I can't really go anywhere except the top part where it's above the global ground level
You can see some strange blue glow in the background here:

also, I wasn't able to figure out how to change the radius for the volumetric clouds, the curvature setting doesn't really help in this case

I think I should make a separate thread if these are valid concerns at this point

 

Could we have Planet radius or something like that setting to be consistent with the PB sky? Because currently I have no idea, how to properly match them.

 

Also it would be great if we will finally get a spherical variant of Fog.

 

And since there is no Planet Position property it doesn't respect it too?

 

The PBSky itself has spherical fog implemented but unfortunately the whole sky rendering is only applied to the background. We still need an option to draw it ontop of objects, to properly simulate it's atmosphere.

 

Still can't see damn clouds, no matter what setting I change. I'm on 2021.2 a10, HDRP 12 and use dx11.

 

You need to enable them from HDRP Asset settings.

 

Do you think I'm an idiot? Of course I was enable it. I turn everything on, and still nothing.
I see shadows from the clouds, but no clouds. I increase camera view on 50000 but no clouds on the sky.