Using skylight in an interior

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1

Hey, guys. I’m making an interior scene with one big window using lightmass and i’m having trouble figuring out if there is a point in using a skylight in these circumstances or not.

The thing is, i don’t understand how this light is supposed to be used. So it takes HDRI or turns scene around it into one and does the same thing as reflection capture based on that? But also adds light to objects instead of just reflections? How does it add light? In this documentation we have this example. Before skylight and after. So the only big difference to me is the bottom parts of the building that were really dark, it kinda affected colors in other parts but not by a lot. So it took HDRI and then what? There is a bounces setting in lightmass for skylight so there are rays of some sort but i do not get where are they coming from.

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I saw people saying that it’s used in interiors to add ambient light into areas that are too dark. Why can’t i just increase indirect lighting of other lights inside the scene instead?

I read the documentation and watched some youtube videos but i still do not understand if i’m using it the correct way and it’s just not useful in my case or i’m supposed to take intensity way up or… Like with directional light i get the logic of it, sunlight goes from this side, hits, bounces, picture pretty.

Any explanation / advice / video would be helpful.

2

The big thing is, apart from me not getting the principle, i do not get what it’s doing that other lights can’t do I guess.

3

Well, okay, i get the HDRI part of it. But then what’s the point of “captured scene” setting?

4

Basically yeah. It’s not a reflection capture although the capture from the skylight is used as the fallback for reflections in your scene. Reflection captures are only used for reflections, not to compute global illumination or bounce lighting.

The skylight sends light into your scene in a hemisphere similar to the way atmospheric scattering would in real life. The light from the sun hits the atmosphere, bounces around the particulates in the atmosphere, and ultimately some light comes out in all directions (though not equally).

The second image in the example shows global illumination computed for the skylight, meaning the light that is coming from the sky is hitting surfaces, bouncing off those surfaces and lighting up the scene.

The skylight simulates that light.

A skylight should basically always be used whenever you have natural lighting coming from outdoors. For example you would not need a skylight if your whole scene was a windowless basement, but for an office with windows to the outside, you would need a skylight.