In 4.18 I have made it so that if you apply a Volume material to a static mesh, the bounding box of the mesh gets the Volume material applied to it, instead of a sphere. This gives a lot more control over the shape of the fog you are adding. The next step which I haven’t implemented yet is to allow the Volume material to sample the local mesh’s distance field. Then you can make fog in the shape of any static mesh, while having the inside of the mesh filled as well.
It does seem as though this specific kind of light bleeding has become more pronounced with the new volumetric lightmaps in 4.18, though. I’ve generally had good success by using thicker walls or invisible static shadow casters, so it’s not a huge issue.
I don’t suppose it would be possible to enable cascaded shadows for volumetric fog but *not *actual shadows, would it? I like having area shadows from baked lights, since they’re cheaper and a bit better looking than distance field soft shadows, but I’d also like to avoid light bleeding through walls onto the fog.
[Bringing this Thread Back to life]
I was a jolly time With Volumetric Lighting and i noticed something that begs for a better explanation [Due to the fact that i do not even know how Shadowing Works in Engines]. I was not happy with when i made the Volumetric Lighting show the Jittering and i couldnt get the History Blend to blend the Jittering so i didnt see it; So i got mad and just turned off Temporal Re-Projection and i noticed the Voxels are made up of pixels. Playing Dark and Light Enlightened me on Shadow quality through Console so i decided to bring the shadow’s quality down to the 1 Knob. To my surprise the Voxel Lighting matched the Volumetric Lighting’s Voxels. Thats no surprise but i wanted to know if the shadows have the exact same type of rendering the Volumetric Shadows do compared to the Shadows. And if not; Is there a way to do the Voxel’ation with the same type of rendering the Shadows have? Or is that just not possible?
Hi there - what Doctor Fail and others are asking - about volumetric fog on mesh - im also really looking out for.
The thing is that we know it was somehow possible - from the car from the youtube video - even though it had few limitations.
But how was that car material setup? - anyone that could answer that would be really appreciated.
Because now in 4.18 if i add the material - in any way - i think it only work on the not so useable - box shape (bouncing box - as DanielW say.)
I hope anyone can help.
Thanks.
Hi,
Recently I started having trouble on my light shaft bloom.
When I’m in editor, it looks fine, the sun is blooming in the sky. However, when I press play there are times where the bloom stays there, but most of the times the light shaft bloom vanishes.
I have a blueprint that changes a bunch of variables during construction (directional light, sky light, fog and a sky material) and later a runtime (dynamic sky cycle). I do recapture the scene for the sky light to work properly. Is there any option that I need to recapture to ensure that my fog is updating it values?
Thank you and keep up the great job on it!
So I’ve been using Volumetric Fog to create some more interesting lighting in a level I’m working on. In 4.17, I had to use stationary lights (even though these lights should be treated as static) in order to get volume lighting.
I can thankfully now switch to Static Lights, save some performance and take advantage of the new Volumetric Lightmap system - but there is one major issue. Volumetric Scattering Intensity has no effect when using a static light (in fact, it’s greyed out), and I can’t work out how to make static lights contribute more to the Volumetric Fog without bumping the light intensity and affecting other aspects of the scene.
I think I understand the technical reason as to why this is, but is there a workaround?
4:18 (Stationary Lights. Red Lights have VSI = 150.f, Light-Shaft is a spot light with VSI = 4.f)
https://forums.unrealengine.com/filedata/fetch?filedataid=123388&type=thumb
4:18 (Static Lights)
https://forums.unrealengine.com/filedata/fetch?filedataid=123389&type=thumb
Notice also that when using static lights, I get an ominous ‘white’ glow from the light too? All colour information seems to have been lost.
Another issue I’ve noticed - static lighting on Volumetric Light Maps only shows up in the editor if you’re using ‘Game’ preview mode. You have to keep pressing the ‘G’ key to see it 
Not super intuitive…
EDIT: Okay I’m not sure what’s going on, but Volumetric Fog just keeps randomly disappearing from the scene. it seems to be related to building lighting and/or showing the volume lighting samples. Something isn’t right here…
It could be implemented easily but we don’t plan to - that would be a huge amount of shadowmap rendering cost just for volumetric fog.
Shadow depth maps are rendered once for each light and then used by both regular surface lighting and Volumetric Fog. So if you lower the resolution of the shadowmaps, it will affect both. However volumetric fog also goes through some volume textures (with the temporal reprojection applied) which is typically much lower resolution than the shadowmap, so that will be the limiting factor on shadow sharpness most of the time.
It’s because once lights are put into the lightmap (either volumetric or surface), there’s no way to separate them out when applying the lightmap to various parts of the scene like fog.
The only workaround I can think of is to make the light Stationary - then you have full control over how it is applied to each part of the scene, since the renderer will loop over all stationary lights per pixel / voxel. Of course, this costs more.
I can’t see this in your screenshot. Just guessing at what you are seeing though, it’s probably from the limited directional lighting representation used by the Volumetric Lightmap. We use 3rd order SH which is actually a ton of data (27 values per voxel) but still limited in what it can represent.
Found a potential bug with samples outside of the lightmass importance volume, see here: Volumetric Lightmap Samples bug (Reproduce-able) - Rendering - Unreal Engine Forums
So, as far as I understand, shadow quality settings determine the quality of volumetric fog, most notably in the form of disabling the fog completely on ‘Medium’ and lower settings.
Is there a way to keep volumetric fog enabled independent of the global scalability settings? I’m evaluating whether to use the fog as a gameplay element in certain situations, but for that to work I’d have to make sure that it’s always there and can’t be disabled merely by tuning some of the game’s graphics settings.
You can customize the scalability settings. It amounts to .ini modification.
Yep as Dementiurge said, you can override scalability levels in your project to force volumetric fog on for all scalability levels. The reason it gets turned off on Low and Medium is because of these lines in BaseScalability.ini:
[ShadowQuality@0]
r.VolumetricFog=0
[ShadowQuality@1]
r.VolumetricFog=0
Nice, thanks to both of you, I will have a look at those.
Hey guys. Is there by chance an ETA on when this fog might support Ray Traced Distance Field shadows? So torn between the two feature sets, would rather have both 
Thank you.
Oh noes 
Trying to move my nice space nebula thing from 4.16 to 4.18, it goes from this:
to this
What’s happening???
Mesh for the particle beam is still fine btw:
Is there some small setting that’s been added in 4.18?
(pleeeeeease be a small setting not a major bug)
