Anyone using a stationary skylight with a dynamic sun for a day/night cycle?

I’m working on a small open city environment with a time of day system, given the limited size of the environment I thought I could use a stationary skylight to get some of the benefits of baked indirect lighting while also keeping a dynamic sun to control the time of day. My plan was to just change the color/intensity of the skylight at runtime as the sun sets.

But I’ve run into a couple of frustrating problems.

  1. Bounce lighting is apparently completely static so although the intensity of stationary lights can be changed, the bounces are still full strength even with the light at 0 intensity. My solution thus far has been to severely limit the indirect lighting strength and then use the exposure controls to try to hide the rest. It works okay but I may just end up scrapping indirect lighting entirely and just using it for AO…
  2. I thought the baked lighting would store some shadow or ambient occlusion information in the volumetric lightmap but this doesn’t appear to be the case, so moveable objects are fully lit by the skylight in tunnels and interiors. I’m used to dealing with this through exposure modification in dynamicly lit scenes but that won’t work in this case because there’s such a huge disparity between the baked statics and the moveables.
I'm really baffled by this one because the older indirect lighting cache DOES properly shadow moveables in occluded areas while VLM does not. I don't really see any solution to this other than ditching VLM entirely.

Has anyone worked with this kind of setup that can give me some advice on how you dealt with these? (or other problems I have not encountered yet?)

Screenshots of the problem I’m having with VLM and a comparison with ILC on a moveable cube

Was wrong about VLMs, they do store shadow information. The default cell detail size is 200 though which is massive, essentially requiring at least a 2m thick wall to avoid light bleed.

They do. But they do not store Ambient Occlusion mask data unfortunately.

Make sure you’re using a lightmass character Indirect Detail volume anywhere where quality of lighting on movable meshes is important.

I’m using them but as far as I can tell they don’t do anything when using VLMs, they only affect indirect lighting cache.

The problem seems to be that UE4’s ability to intelligently place VLM samples is based on how much indirect light is coming from the light source, by turning down indirect lighting on the skylight, UE4 can’t effectively figure out where to place samples because AO isn’t taken into account (which I think may be the point @2car was making above)

I don’t see any reasonable solution to this. Seems like VLMs just won’t work for this lighting setup.

You can try on the visualizer to see the samples in the viewport options.

Yes I am well aware of that…