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How to get good quality shadows from static sky light?


I'm having issue with illuminating my scene with sky light.

On a screenshot below, light is baked with static skylight and stationary directional light. Directional light gives nice baked shadows, including shadows from light bounces. However, as you can see, there is also a lot of "noise" around it - it's what I get from baking skylight.

I want to achieve a smooth "glow" effect around the place where directional light hits the room. But no matter what settings to I use for lightmass, my skylight shadows are dreadful!

Is there a trick for illuminating scenes with skylight correctly?

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Product Version: UE 4.19
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asked Jul 14 '18 at 06:33 PM in Rendering

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2 answers: sort voted first

I figured out what was causing the issue.

I turned sun brightness on sky sphere from 50 to 300, because I wanted to get the smooth glow of the sun disk, instead of it being just a white circle in the sky.

And because of that, skylight went crazy, and made that terrible shadow noise everywhere.

I thought sun brightness on sky sphere was purely cosmetic. But I misunderstood how skylight component works.

After I set sun brightness back to 50, my scene is lit correctly. However, now I can't make the sun to be "glowing". If I crank up bloom in post process, it messes up reflections so badly that they become blinding, filling the entire screen with white. And I can't increase sun brightness on sky shpere either, as it turns out.

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answered Jul 16 '18 at 02:27 PM

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I would raise the lightmap resolution of the bed. Turn off compression on your lightmaps... ...and would raise indirect lighting quality to 4-10! Are you using a HDRI cubemap? Do you have portal(s) in your opening(s)? ...lightmass importance volume?

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answered Jul 14 '18 at 06:52 PM

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avatar image Kligan Jul 14 '18 at 07:25 PM

Bed's lightmap resolution is 512 (the frame is separate from sheets and the pillow, so it's 512 for the frame only)

Static light level scale 0,1. Indirect lighting quality 10. Indirect lighting smoothness 1.

No cubemap.

I do have portals and lightmass importance volume.

I did not turn off the compression, but I'll try it next.

I tried to to bake only skylight, without direct light source, to test the results. And it gives this nasty noise where its most intense light hits the surface. Indirect shadows are good, however. The entire scene looks great, except for those parts where sunlight from skylight hits surfaces.

If I turn off sky light, and bake only directional light. then all the direct shadows AND indirect shadows are good. But the scene is not lit properly w/o skylight.

avatar image Makigirl Jul 14 '18 at 07:41 PM

Do you have any emissive light in the scene? What is the number of Skylight bounces? ...yeah those usually come with skylight... Also... any 2 sided materials?

avatar image Kligan Jul 14 '18 at 07:42 PM

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I've baked the light w/o compression. As you can see, places where lighting from skylight touch surfaces are all terrible nonetheless.

avatar image Kligan Jul 14 '18 at 07:50 PM

I have two-sided plants and some paper.

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No emissive lights (I haven't even touched that yet, don't even know how to use it).

Number of indirect bounces 10, skylight bounces 5

avatar image Makigirl Jul 14 '18 at 08:59 PM

What is your Skylight intensity? ..any extra turned on like higher illumination than the default 1? ...for a reason you don't get enough samples that's why the spots... are these production bakes?

avatar image Kligan Jul 14 '18 at 09:10 PM

Skylight intensity is set to 3. Skylight indirect lighting intensity 5. I tried baking skylight with intensity 1, but it's still the same, except everything is darker.

This is medium bakes. I tried production bakes, but it's not much different - skylight still messed up.

avatar image Kligan Jul 14 '18 at 10:09 PM

I've created new project, imported some of my meshes, and set up a scene with minimum stuff in it and similar lighting settings.

Here's how it looks with ONLY directional light baked:

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And this is how it looks with ONLY skylight baked:

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Baked directional light looks great. Skylight, however, looks absolutely terrible. I can't figure out why!

1.png (1.9 MB)
avatar image Makigirl Jul 14 '18 at 10:16 PM

Yes those are familiar... seen them a LOT! :D :S But with those settings you shouldn't have had them... ...would you mind sharing any of your scene (privately)? Would be easier for me than just guessing! ;)

avatar image Kligan Jul 14 '18 at 10:31 PM

How do I do that? I can't seem to find a way to send a private message in here... Am I blind?

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