Night and Day cycle with global illumination

Development Rendering
1

Hi everybody

I’d like to have a Night and Day cycle with dynamic global illumination or fake if dynamic is not possible.
My scene will be static only the day cycle is gonna change. Also a few light switchs on and off in the house but that’s about it.

All the tutorials on day cycle i could find for now don’t have global illumination.

Here is an example of what i’m trying to achieve
https://www.youtube.com/watch?v=3t70NsbIUoQ

I had an idea i don’t know if it’s possible it would be to precalculate multiple lightmaps for every hour for example and having those map to transition from one to an other.
It’s fake but it could work an cost probably less in terms FPS loss.

Thank you

2

Could this help? I’m very new to UE4 and I was thinking about this. Also about Alien: Isolation, they have some nice baked global illumination but they are able to adjust it (eg. scene which “lights up” objects and global illumination still seems nice and well “blended” with dynamic lighting(?)).

From https://docs.unrealengine.com/latest/INT/Engine/Rendering/LightingAndShadows/LightMobility/StationaryLights/index.html

"Indirect Lighting

Stationary lights store their indirect lighting in the lightmap just like a static light. Indirect lighting cannot be modified at runtime by changing brightness and color like direct lighting can. This means that even when a light has Visible unchecked, its indirect lighting will be put in the lightmap during the lighting build. IndirectLightingIntensity on the light can be used to scale or disable the indirect lighting from a given light at lighting build time.

However there’s a post process volume setting called IndirectLightingIntensity which lets you scale the contribution of the lightmap for all lights, which can be changed at runtime from a blueprint. "

Edit: There’s LPV (not production ready) for dynamic GI: Lighting the Environment in Unreal Engine | Unreal Engine 5.1 Documentation

3

Currently there is no great solution for dynamic GI in UE4 (sadly), you can fake GI or indirect light, though. I have a system set up that uses a (moveable) skylight that has its colour changed depending on the angle of the sun. There is no real hit on performance from it and it looks acceptable (but I will definitely be changing my system once a good dynamic GI solution is in UE4).

4

Ok that’s what i tought and read already on the subject.
Thank you guys!

5

FWIW I’ve been playing with LPV and it’s not too bad.

6

VXGI is way better than LPV but still miles behind lightmass quality-wise…have to make sacrifices…quality or interactivity :stuck_out_tongue:

7

Does your game consist of mostly terrain by any chance? If so perhaps you can use heightfield GI. It only works on terrain though, not static meshes.

8

I have something like this faked by crossfading multiple global screen space effects. It’s not perfect but works well enough with my cartoonish style.

9

Something that I was working on, but haven’t in awhile, was to have basically two sets of lighting. Wherever I would place a light, I would add a second one that has the right color settings. When the cycle switched at a certain time blueprints would shut off the Daytime Setting lights and turn on the Nighttime Setting lights. Probably was not the best way to do it, but it worked for me! :slight_smile: