UE 4.25 Sun and Sky Actor - too bright at night. How to control ambient light?

I’m using 4.25 and trying to use the new SunSky actor, but when moving the sky (using ctrl+l) to mimic night, the scene is still very bright.

Usually there’s an ambient light, which is fine, but it seems too strong. How do I control it?

Do you have fog in there? That will be the problem…

You need to adjust the auto exposure, also try setting the sky light to stationary mode and rebuild light maps.

Is “Lower Hemisphere is Solid Color” disabled? If so, enable it and try to adjust color / alpha to get intended results…however, it’ll most likely require adjusting skylight and atmospheric fog / height fog settings too.

I can’t build light maps since I’m using dynamic lighting (open world game).
Changing the light to stationary doesn’t seem to do anything.

I understood I shouldn’t use fog with the new sun & sky actor. am I mistaken?

You should use fog, both atmospheric and height fog. It’s just a challenge to get the exact settings for a particular effect, such as an ambient night. I think you’ll need some form of volumetric scattering to enhance the ambience, possibly with a lower height atmospheric fog or sky atmosphere effect. A second atmospheric fog might do it, too, that is set distant from the camera and comprises a much shorter range of the atmosphere (ground to top of sky) than the first atmospheric fog. However, the Mie and Raleigh Scattering in the Sky Atmosphere could be modified to get the enhanced ambience with a night sky. The first step, I think, is getting the correct color of the night sky and horizon.

Or just wait until 4.26 is released, they said, they made a few changes and improvements for atmosphere, sun&sky, day&night etc.

If you change your Sky Light to Stationary, then light building will make light data for your Sky Light. You don’t need to change the Sun actor. In dynamic mode Sky Light uses just uniform ambient light regardless of the Sun mode (dynamic or stationary). Of course if you set “force no precomputed lighting” then it won’t work.

@HorusWM “In dynamic mode Sky Light uses just uniform ambient light regardless of the Sun mode (dynamic or stationary)”
Ambient light from where? what amount? how do I change it?

@presto423 Do you have any guide or spceific instructions I can use for something ot start with? I tried to use them but just adding them to the scene, each one, and trying to play wtih them seems to be really bad.

This is what my night currenty look like, at 20.0 solar time, with 1 sun light (SunSky actor with 75000.0 lux lux) and 1 moon light (directional light with 0.26 lux and colored):
The color isn’t that bad, but the sun it self looks really weird.


When I add Atmospheric Fog:


After playing with the Atmo fog:


Whn I add Exponential Height Fog (and removing atmo fog):


I tried to change all the parameters in those objects, but it didn’t look any better.
What am I missing here?

I don’t have a guide, which would be really nice for that in my estimation too. I learned by changing settings and seeing the effects, and repeatedly reading the doc page on those things. I’m missing some things too, in my knowledge, and don’t remember everything when I’m doing it. It requires some amount of practice to remember and understand the different facets to get specific results and improve them, and is something I need to do too.

So, is the wide, orange thing in picture 1 (without atmo fog) the sun? I think it is appearing to not be fully below horizon, which I think is probably due to the 20:00 sun time, at least partly. What is the latitude and longitude? The darkness level looks correct for that picture. Are you able to share the project? Simply right-click the project folder it’s in and select “Send to > Compressed Folder” and confirm to place it on the desktop. It’s the easiest way to zip it and share it because it’ll be a far smaller size to upload to the forum thread. I’ll look at it and see what I’m capable of doing to fix the two issues of the weird sun and overexposed atmospheric and height fog.

I think it’s the sun, but your guess is probably better than mine.
I understand what it’s suppose to look like, but the result is weird imo. Don’t you think?

Also, why is there no “moon disk” at night? That is, I can see the sun it self when looking at the sky during the day, but not the moon when looking at the sky during the night.

the latitude is 45.0, longitude 73.0, time zone -5.0, north offset 0.0, month 9 day 21.

I can’t share the project since it’s both private and really big, but I can try and replicate the same env on a new project.
It’s gonna take me some time though, so if you (or anyone else) have any more tips/information on what I can adjust to achieve better results, please do so.

Right, you asked about the disc from my moon in that other thread ^.^ For my moon, i just had raised the “Source Angle” to 4, to get this nice disc.

And i think, some devs mentioned, that you should not add another atmospheric fog to your scene, if you have sky atmosphere. The Sky Atmosphere is the newer version of the atmospheric fog and replaces it, they basically do the same job. So adding both to your scene will cause false results.

Exponential height fog, that you can add to your scene, but i think, that caused some trouble right now, and will be addressed in 4.26. If i remember correct, it was mentioned here:

At min 15:00, they talk about sky atmosphere and exponential height fog, and at 15:32 they say, that the atmospheric fog is NOT compatible with the new sky atmosphere :slight_smile: but the exponential height fog is, and it will be used for getting more control over the fog.

Edit: ok, they also adress how to set up exponential height fog with sky atmosphere shortly after taht, so keep watching.

Yes, it looks weird. For that lat/long location, the day is transitioning to night, but I’m not sure at which point in the transition your scene represents more exactly. AFAIK, a second directional light set as a sun is one way to get a moon, but there’s other steps involved. And I think that video posted above covers it, or another Unreal featured video does.

@presto423 I’ve actually watched that video, multiple times. While it actually some properties about the new system, it doesn’t explain nor even use the actual Sun & Sky actor, so I can’t actually follow it. It seems like the default settings don’t match.

Also, I tried to follow specifically the fog instructions you mentioned. Didn’t do much either.
Without the fog:

with the fog:

I tried to look for a specific video with the Sun & Sky actor but couldn’t find any :\

That fancy Sun & Sky actor is just a compilation of several light components, that you usually drag into your scene one by one. So it does not matter, if you use a Sun&Sky actor, or if you drag in a Directional Light (for the sun), a Sky Atmosphere, and a Skylight by hand, and adjust them one after another. The only fancy part, is that the compass and the lights are connected and will moving according to the time, you set there. But they are still all the standard components, you would use in a normal scene, just that you then set them manually into position (or you wire them by hand and make your own blueprint, f.e. for including an exponential height fog ).

Those here are the components, your Sun&Sky contains, it´s just dragged all those into a blueprint for making things easier, but they are still the same as the normal components:

Another thing might be, that the exponential height fog might look all black, because there is no actual ground or landscape for it to interact with. In the Video from Epic, they have this massive landscape (and look from pretty high above), from which light can be reflected back into the fog. Without a big plane as ground, or actual landscape, it just might become black, because all the light vanishes into underground, and the fog just represents this darkness as a result of this. Try to bring in a plane as ground, and increase it´s size to really really big, and check, if that makes the fog more appealing.

Edit: Ah, i also usually use a PostProcess to change the Bloom for the Lights to “Convolution”, to get the better sundisc.

(and i am not Presto ^.^ )

Sorry about the name mixing :stuck_out_tongue:

Yes I’m aware of that. But:
(1) In the mentioned videos they usually only bring some of the components and not all of them, and making them all play together isn’t shown or explined in those videos.
(2) Either way something is different. It’s probably just the default values, but since it looks completely different and playing with the values doesn’t seem to get the same result - it’s still a problem.

I’m already using a landscape. It’s probably not as big as what they were using, but still.
And I tried using a really big plane, it didn’t do anything :\

Can you post a screenshot of the SkyAtmosphere settings (with all advanced settings too, from clicking the dropdown arrow to display them)?

There’s at least some difference between the SunSky actor and placing each component in it in the scene, separate from having a SunSky actor. One major difference is the compass and lat/long system, and another is how the SkyAtmosphere settings getting modified causes changes in the lighting and visibility / look of the sky. Overall, the two methods are similar, though. More information is needed to get a better idea how to help fix that strange sun problem. So, providing SkyAtmosphere settings in a screenshot, and some settings of the directional and skylight would really help. I honestly don’t know exactly how to create a moon disc, but have seen a video or two that contain instructions for how to do it, I think, which were on youtube and/or in the docs / learning area of the Unreal site. If you really want to understand how to do it, it’s better to research it in-depth rather than waiting for a developer to do a whole write-up of it in the forums.

@presto423 There’s no real point to it though; I didn’t change anything. I went over the properties of it, there aren’t any “yellow arrows” (that one that reset the value to the default, and disappear when it’s already on the default value).

The only thing not-default I have is the moon actor: a directional light.
Changed properties:

  • “Atmosphere Sun Light Index” set to 1
  • Intensity set to 0.26lux
  • color set to light-blue

And I’ve went through some other tutorials and vieo about UE sun & sky atmosphere, didn’t saw anything about the moon disc with the new sun & sky system.
If you know a specific video or docs/page about it, I’ve love to see/read it!

I tried basically the same settings for lat/long (except Long is -73, though I think that’s what you were using), adjusted exposure a bit (Compensation -2, and 0 for both Min & Max on Histogram Mode), and increased the second directional light (moon) intensity to 1 lux to light up the surface of the floor more. I think brightness is strongly influenced by exposure settings in the post process volume with the basic scene setup instructions for a night sky. However, it’s also a factor of the material being used. What is its base color values / texture? Diffuse boost or emissive in it could increase how brightly it appears in the scene, though emissive is quite different when changing it. Is the material in your project a Quixel Megascan?

To get rid of the weird sun arc converging over the horizon, try setting Rayleigh Exponential Distribution to 1. Or if it’s intended to be kept as a sunset, it’ll probably require a blueprint and/or some modifications to Sky Atmosphere and Post Process settings to enhance.

After some testing, and looking some videos again, i noticed, that even the devs changed their directional lights down to 10-12 lux for the intensity, so maybe that is a hint, that some parts from the exponential height fog or sky atmosphere are not working properly with that insane value, that this blueprint comes with.
Even in the video from the previous, site, he used a light with just 12 lux, not 50000 or 75000. And i got that bad looking band too, after going beyond 50 lux.

Maybe they change it with 4.26 or UE5, so that those things work better with their own stuff :confused: