Hello, I’m noticing an issue with Sky Atmosphere and interiors. In a simple map with a directional light and a sky atmosphere only, I am getting a lot of very bright atmosphere in a completely closed interior. I am working on a game where we will be going in and out of caves a lot, so I can’t disable the atmosphere as you will still see it through openings like doors, cracks in the walls etc… Is there anyway to disable it’s effect in interiors? I’d expect this to be completely devoid of any light.
Looks like exponential heightfog honestly. Fog color is additive and unshadowed when volumetric fog is disabled, so you’ll run into this issue in interiors unless you enable volumetric fog.
Clamping the exposure and/or setting a fog start distance can also help in some situations.
You’re right, the Sky Atmosphere and Exponential HeightFog components in Unreal Engine often add atmospheric effects even in completely enclosed interiors. This isn’t always the desired behavior, especially for scenes with caves or interiors that should be devoid of external lighting influences.
Here’s how you can fix or mitigate this issue:
- Volumetric Fog: As you mentioned, enabling Volumetric Fog in the
Exponential HeightFogcomponent can help. Volumetric Fog respects the light’s shadow, so areas that are in shadow (like the inside of a cave) will not have fog. - Fog Start Distance: Adjusting the Fog Start Distance will determine at what distance from the camera the fog will start. Setting this to a suitable value can help prevent fog from appearing too close or inside interiors.
- Light Channels: Unreal Engine has light channels, which allow you to specify which objects are affected by which lights. You could potentially use this feature to have a different set of lighting for interiors and exteriors. This way, you can control the lighting in interiors without affecting the exteriors.
- Post Process Volume: Create a post process volume inside your interiors/caves. Make sure it’s set to Unbound =
False(so it only affects the interior). In the Post Process Volume settings:
- Adjust the
MinandMax Brightnessvalues to control exposure. - Consider tweaking other settings related to ambient occlusion or indirect lighting to fine-tune the look of your interior.
- Shadowing: Ensure that your interior is well-enclosed and that the directional light isn’t leaking into the interior. Light leaks can sometimes be the culprit for interiors looking too bright.
- Ambient Cubemaps: If you have any ambient cubemaps or reflection captures inside the cave, ensure they aren’t contributing to the brightening of the interior.
- Lightmass Settings: Ensure your light bake settings are correct. Sometimes, increasing the quality or adjusting certain parameters can lead to more accurate lighting inside interiors. Make sure to check the Lightmass settings in World Settings.
- Consider a Dynamic Solution: If you’re going in and out of caves frequently and the lighting conditions outside the cave might change, consider using a more dynamic solution. One method is to use a combination of Blueprints and materials that detect when the player is inside a cave and adjust lighting or atmospheric parameters accordingly.
Remember, achieving the perfect look often requires a combination of techniques and fine-tuning. By using the methods above, you can control the lighting in your interiors and make sure they look as intended
Unfortunately no, there is no height fog in this example, that’s what I thought at first, but this atmosphere actually makes volumetric fog much brighter when it is enabled.
Here’s an example using a realistic sun value for example (100,000 lux). In a completely closed room, I’d have to clamp my lower value to well above 5ev. At a very low value (10lux) I’d have to clamp it to -3ev, but I still see some atmosphere filtering through the walls.
Thanks, I’m trying to keep this as simple as possible for now, I’m just trying to make sense of how the atmosphere works. I should mention I’m using Lumen, so light baking/lightmass isn’t really an option at the moment.
As for volumetric fog, start distance will push back the fog, but the atmosphere remains, which is why I’ve disabled it completely for this test.
So far it seems my best option is to trigger off the exterior lighting once I enter a cave, but ideally, this would happen a distance away from the door, in case there is detail outside we want to see.
The problem you’re describing is related to the Sky Atmosphere in Unreal Engine and its interaction with closed interiors. Here’s a step-by-step approach to address this issue:
- Distance Field Ambient Occlusion (DFAO): Ensure that you have Distance Field Ambient Occlusion enabled. This will help in determining occlusion for indirect lighting, including the Sky Atmosphere’s contribution.
- Go to Edit > Project Settings > Rendering.
- Make sure Generate Mesh Distance Fields is enabled.
- On your directional light, enable Affect Distance Field Lighting.
- Mesh Settings: Ensure the meshes forming your interiors/caves have proper distance fields. The mesh quality, especially for static meshes, plays a big role.
- Open the mesh in the Mesh Editor.
- Go to the Details panel > Build Settings and adjust the Distance Field Resolution Scale. A higher value gives better distance fields but at the cost of memory.
- Tweak Sky Atmosphere Settings:
- Open the Sky Atmosphere settings in the Details panel.
- Adjust the Rayleigh Scattering, Mie Scattering, and Absorption parameters to values that minimize the undesired effects.
- Material Assignment: If your interior walls have materials assigned to them, ensure that they are not semi-transparent or subsurface, which could allow light to pass through.
- Lighting Quality and Bounces: Unreal Engine uses global illumination which involves light bounces. In your post process volume, you might want to reduce the number of bounces to a minimum. Also, make sure the Indirect Lighting Intensity isn’t set too high.
- Post Process Volume: Use a post-process volume to control exposure inside the caves.
- Create a Post Process Volume in your level and scale it to cover your cave or interior area.
- In the Details panel, enable Infinite Extent (Unbound) if you want it to affect the whole level or just scale it to cover the specific cave area.
- Adjust the Min Brightness and Max Brightness under the Exposure settings to control how bright or dark the interior becomes.
- Light Propagation Volumes (LPV): If you’re using Light Propagation Volumes, this might also contribute to light leakage. Ensure that LPV settings are properly configured to minimize undesired effects.
- Shadows: Ensure that the Directional Light’s shadow settings are appropriately set. The Dynamic Shadow Distance and Cascade Distribution Exponent can be tweaked to get desired shadowing results which can affect the atmosphere’s behavior.
Lastly, always ensure that your engine version is updated. Unreal Engine is constantly evolving, and certain issues might be addressed in later versions
How large is this interior? I’m not able to reproduce this without an exponential heightfog.
SkyAtmosphere component has its own heightfog called aerial perspective, by default it starts 100m from the camera so if you have a very large interior, it could conceivably leak inside. You can adjust the start distance from the “aerial perspective start depth” in the SkyAtmosphere component settings, increase the value and it should push the aerial perspective further out.
Hi, yes it’s quite large actually since the map our level team is putting together is very large. This example was huge 300m wide by 100m high ( I think, still getting used to Unreal Units). I’ll try making this much smaller and see if it’s still happening.
Aerial Perspective Start Depth seemed like the perfect solution when I was trying it yesterday, however it seems at this very large scale, with a very bright sun (100,000 lux), even setting it to start 1km in the distance I am still seeing it.
The intensity of the light shouldn’t make any difference, since the aerial perspective doesn’t even start until the specified distance. Whatever lighting remains is probably some other form of light leak.
Hey again,
After adjusting the scale of the room to something more reasonable (4m x 4m to 40m x 40m)and adjusting the aeriel perspective start depth, I was able to drive the atmosphere out of the room.
Thanks so much for your help
-Alex