How can you use a skydome to bake indirect lighting?

Hi. I have a scene setup with a custom skydome, but I can’t figure out any way to use it for calculating my baked lighting. I’ve also had trouble getting any indirect light pre-calculated from the dynamic sky. If I set the sun intensity to 0 all the lightmaps come out black. My skydome is setup just like the one in the mobile temple example scene, with an emissive spherical cubemap.

Hi Klein. I am one of the environment/tech artists at epic. The feature you are asking about exists only in beta form at the moment. There is a new type of skylight actor that reads the sky dome and uses that for indirect lightning. I apologize I am away from my computer at the moment but I will track down the exact name and settings required later tonight. That said, I wouldn’t be surprised to come back and find somebody else did an entire write up of the beta feature like what happened with lightpropoagation volumes. I have been very impressed with how deep some people are digging into the engine and how helpful people are sharing their findings.

I hope to post back with more information later tonight if nobody beats me to it.

Go to Window -> Class Viewer.

Type skylight

Select the Skylight class and then drag it into the world. Or right click in the viewport to add one.

You will have to rebuild the lighting in order to see it reflected on your meshes. You may also need to adjust the sky distance threshold depending on how far your sky is. You can also specify a cubemap instead of using the scene.

Please let us know if you have any issues.

Hi Ryan, thanks for looking into it. I found the skylight and I’ve been using it in my scene. It works great on dynamic objects, but the vast majority of my scene is static. Is that the feature you were saying is still in beta, or is there something else in the works for a future update?

Just to back up, I have an interior scene in a forest with a couple open windows, but no lights. The sun is angled so that the room gets some direct light from it, and its also the sole source of indirect contribution at this time. Its working well enough, but the room’s lighting lacks a lot of the subtle color variation such as the green values it would get from my cubemap environment. I was hoping since the cubemap was emissive it would contribute to the static lighting, but that doesn’t seem to be the case. My current workaround is to fake it with a large static spotlight. I set the color to match the environment, put the intensity at 1.0 and the indirect intensity at 35,000. Its not the most elegant solution, but does seem to do the trick in this case. Looking forward to future lighting improvements!

THAT’s what the Skylight does??? Smart :)! I thought my lighting had changed subtlety since dropping my sky in there.

Out of interest does it work on blueprinted skies? I guess it takes the average colour of meshes > a certain distance away per-frame and calculates it that way?

Since I’m bored on my phone I thought I’d revivie this old thread just to say: this is possible without a skylight now (skylights affect the whole level so aren’t an option for everyone). Just give your skydome an emissive texture and tick the “Use emissive for static lighting” box on the static mesh actor.

  • The skydome mesh asset (in the content browser) must have Cast Shadows = True, and the skydome actor must cast shadows as well. Else it will not be included in the build.
  • The skydome needs to be as close to the world as you can allow without it looking silly. The further it is away, the more you need to increase EmissiveBoost to get it to light things.
  • The centre of your skydome actor’s bounds (not the pivot) must be inside your LightmassImportanceVolume. Else it will not be included in the build.
  • There is now a world setting for more skylight bounces which I believe affects emissive bounces too, so you can get nicer bounced lighting.