Hello,
I’m making a 3d small open-world (not so opened then) which has exteriors and interiors. Because my interiors receive no lighting otherwise, I had to switch my directional light mobility from Movable to Stationary. However, I also would like to have a Day/Night Cycle. Realism is quite important, so I hope I can have dynamic shadows with my cycle. How can I achieve this ?
You can’t achieve this without sacrificing realism.
Okay. That’s clear. So I get to two derived questions :
- If I choose to have a movable directional light, how can I light up my interiors that are almost completely black (a bunch of windows isn’t enough)
- If I choose to have a stationary directional light, how can I simulate a day/night cycle ?
Simplest way is to just add a skylight and ensure Lumen is disabled. It will beam light in through walls. If you’re using Lumen then you just need to adjust your exposure.
Otherwise, you can use fill lights or an ambient cubemap. I would avoid ambient cubemaps though personally.
In my opinion the best option when not using Lumen is to use a moveable directional light, and a stationary skylight set to 0 bounces (this forces it to only bake shadows). This will cause interiors to be black, but they’ll have natural loooking skylight shadowing. When paired with fill lights that change their color/intensity with the time of day you can get a relatively realistic result:
This gives the best possible compromise in my opinion. You get moving shadows from the sun, natural skylighting, and skylight shadowing. It works and looks plausibly realistic at most exposure ranges. But it can be tedious to work with as it requires manually setting up fill lights in interiors.
All of the non-Lumen options will have issues with glossy reflections, as reflection captures can’t be updated or tinted at runtime in Unreal.
Change the skydome and fake the lighting change with post processing and changing the directional light color/intensity. The shadows won’t move with the time of day, you will have to just live with that.
what type of stationary are we talking. like baked gi inside? i guess you could bake interiors externally into lightmaps or vertex colors, do it without shadows - just coarse ambience. and use some sort of modulation with the sun light color or skylight. that way you would have basic lit interiors and can do dynamic sun shadows.
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