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Dynamic Interior and Exterior Lighting

I've been running into an issue since I started using the Unreal Engine for my project well over a year ago. The project is a single seamless world with the exteriors and interiors in the form of buildings and cave all streamed together at once; with a dynamic day/night cycle. We use a Directional Light, Skylight,

I've run into an issue making the interiors dark enough, while still having the world realistically lit in the exteriors. The issue is the skylight. If the skylight is bright enough to affect the shadows in the exterior, it's bright enough that caves and interiors are always bright as well. If the skylight is dark enough to not make the caves glow, then the exterior world has pitch black shadows.

We use distance field lighting, but that creates it's own problems with regards to the landscape, as the second a cave intersects the landscape mesh, there is a sharp and distinct transition to being in full distance field shadows; and the issues caused by this simply aren't acceptable in many cases.

We've also used transition volumes and similar trickery in the past, but it always ends up being a very imperfect solution.

What I'm looking for is the best way to realistically light both the exterior world, as well as have dark interiors - without having interior/exterior triggers.

Is there any way to do this, and/or will future versions of the engine be addressing this with the lighting/shadow system?

Thank you for your time.

Product Version: UE 4.10
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asked Feb 08 '16 at 08:26 PM in Rendering

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Hey str-Luke,

The main feature that is going to help with the transition from an interior to an exterior environment is going to be 'Auto-Exposure' or eye adaptation. This causes the exposure of the scene to automatically adjust to recreate the effect experienced as human eyes adjust when going from a bright environment into a dark environment or vice versa.This setting can be found in your global post process volume, but if you do not have one, you can simply add it via the 'Modes' tab.

Take a look at our documentation on this feature as it provides a good explanation of its usage and how it can be fine tuned to suit your needs.

Eye Adaptation


Using this in combination with other post processing effects like 'Bloom' as well as clean dynamic direct and indirect lighting will yield some really great results.

Let me know if you have further questions or need additional assistance.


Andrew Hurley

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answered Feb 09 '16 at 06:08 PM

avatar image str-Luke Feb 09 '16 at 07:51 PM

I don't think that would work in my specific situation, because the issue is that the interiors are already too bright. With eye adaption disabled, the interiors are already very bright, even when fully in shadow (due to the skylight)

I might be able to dial up the exterior brightness to increase the contrast and give eye adaption something to grab on to.

avatar image AndrewHurley Feb 09 '16 at 09:03 PM

You don't want to disable eye adaptation, but enable it and set the min and max brightness to good values. You need to fly around your level and pull up the Histogram, then while looking at the brightest and darkest areas of your scene, get the values to a good range.

avatar image str-Luke Feb 09 '16 at 10:23 PM

The issue is that the skylight is causing shadows in the exterior to essentially have the same exact values in the histogram as the interiors... (Because the interiors literally ARE just in shadows)

I'm trying to figure out a way to get actual enclosed spaces, such as a cave deep under ground to be dark, while the shadows on the surface still get some sort of ambient lighting, At the moment, I only seem to be able to have realistically lit shadows on the surface and unrealistically lit interiors, OR unrealistically dark shadows on the surface, and properly dark interiors.

avatar image AndrewHurley Feb 09 '16 at 10:28 PM

Try disabling the 'Cast Shadows' on the 'Skylight', or try unchecking the 'Lower Hemisphere is Black' option.

This isn't really a bug, but just a need for understanding how lighting works in UE4 and balancing your indirect lighting with the direct lighting and shadowing. It is not easy, but I am sure you can find the correct set up to get your project to render correctly if you continue to experiment.

avatar image Drixil Aug 29 '16 at 04:34 PM

Funny I have been having this problem since I started using this engine 3 years ago and non of these marked answered suggestions works... The only way to do it that I have found is to make a post process volume and put a very dark cubemap in. It takes alot of tweaking because you know dark interiors are really not that common in video games.... No need for that....

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