Studying Realistic Interior Lighting in UE4

Check out this study of realistic interior lighting in Unreal Engine 4 by Filippo Romani. The artist shares tons of tips and tricks for archviz enthusiasts. 

I recently delved into the study of realistic interior lighting in Unreal Engine 4, and after a couple of week of experiments I finally produced a satisfyingly realistic result, a screenshot of which you can see here:

Since a few people asked for a tutorial about how I achieved it, I decided to explain here the basic settings that stand at the foundation of the realism of the scene. To begin with, I’d like to give a disclaimer: I did not model anything of what you see, I only made the walls and floor materials, along with the lighting part.

This said, let’s start from the type of lights used.

Lights

The only lighting source is a directional light (the sun), combined with a skylight. On the other room (the screenshot of which I’ll be posting at the end) there are three point lights, one per lightbulb. All of the above mentioned are stationary, except for a dynamic spotlight that I needed to enable the subsurface scattering effects on the curtains.

Right from the beginning, my goal was to use the least amount of lights as possible. I believe that, although it’s harder to achieve the desired result in this way, using only lights that have a physical source in the scene (the sun and the lightbulbs) gives life to a much more believable scene. Fill lights should be used very very sparingly, as they make the scene flat and boring, other than less realistic.

I set the directional light strength to be only 1, as it looked the correct value for the sun coming in, and gave it some warmth with temperature:

Same for the point lights: a low value (40) and a source radius that realistically resembled the radius of a lightbulb.

Lightmass

Lightmass settings played a fundamental role. Performances were not my focal point, so I had some fun playing with high-end settings.

If you observe a room in real life, you’ll notice how the direct light coming from a window only hits a minor part of the whole surface, and yet manages to bright everything very clearly. It bugged me that a room in Unreal would be very dark even with a big aperture on the outside. I figured that indirect light wasn’t enough.

To overcome this problem, I cranked up to 100 the number of light bounces in world settings, and to 10 the quality of indirect lighting. With a high-quality value you can (and should) bring down the indirect lighting smoothness too. And there you have a nicely indirectly lit room.

Post-process volume

I got rid of most of the autoexposure. I don’t like it very much as I find it too drastic for my tastes, and it also caused the room appear to as too dark. I wanted the directly lit surfaces to shine, but not so much that whenever I watched it everything else became black.

To further bright the ambient, I tweaked the global postprocessing values. They change from scene to scene, so I would recommend to just play around with them until you reach the wanted result.

A tip I can give regarding this matter is to be very careful with saturation. I see a lot of works where everything is bright and eye-candy, but it’s not realistic. The same goes for contrast, so have fun, but keep a critical eye on the result.

The last thing I did was to disable bloom and lens flare. After that, I was ready to bake very high-res shadows (up to a resolution of 2048), and with the build with production quality, shadows fell into place with everything else.

Conclusion

There are many things I didn’t specify, as they are parameters and tweakings that change from scene to scene. The most important thing I learned with this experiment though, is what each setting does, and how to obtain a precise effect I want. That can only be achieved by experimenting yourself with the different aspects of light, and by dedicating some time to that specific purpose.

I hope this helped, and I’ll be very happy to answer questions and doubts you may have.

Filippo Romani, 3D artist

The article was originally published on Filippo’s personal blog. 

Also, check out this scene from UE Marketplace that shows the experimental translation of a former still-rendered project into the Unreal Engine for creating an animation out of it. A talented artist got the desired lighting mood and quality done together with some heavy geometry imports.

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