Best way to achieve this light effect?

[FrankGehry]

I'm trying to create a room with a naturally-lit ceiling (example image at very bottom—Museum Brandhorst). To do this, I'd like to utilize glass skylights that are frosted to create a soft white light. The scene is being lit by and HDRI sky. I have a frosted glass plugged in, but my shadows still seem rather sharp.

I'm looking for suggestions on how I should alter the material to get softer light. I tried to upload my material file, but it keeps telling me it's invalid.

I appreciate any help!

[peerman]

Hi, with some tweaks you can get that result. See this thread.

Best,

[FrankGehry]

Hi, with some tweaks you can get that result. See this thread.

Best,

Thank you! It doesn't seem like anything was ever resolved in that thread. Increasing the sun size could work, but I'm using a HDRI to illuminate my scene, and I also have those windows at the front which would make sharper shadows.

[ValeroStudio]

Why not just place planar lights in the ceiling? I think trying to get that affect with a refraction + HDRI affect will be harder to achieve. Fake it til you make it... is what I always say.

[GD3DESIGN]

Fake it til you make it... is what I always say.

+1

Faking things could save render time, too.

[jiminy-billy-bob]

I made this a while ago. It was made with V-Ray 2.0, but I opened the scene with 3.6 and it renders the same.
It's just a simple 2sided material with 50% translucency, wrapping a plain white material.
There is a huge invisible (to avoid blocking the sun light) rectangular light above the whole structure, to ensure the light is evenly distributed.

[konstantin_chaos]

Hi guys,

The setup described by jiminy-billy-bob is the right way to go.

It can still be optimized slightly:
- The exterior lighting can be done with a Sun & Sky. The 2-sided material should still work
- The big Area lights can be made slightly smaller and placed inside. They should be invisible and with their Affect Reflections and Affect Specular options disabled
This way you'll have some direct light in the interior, not relying 100% on the GI calculation.
It'll improve the quality of the lighting and should be faster to render (much lower GI quality will be required).

Regards,
Konstantin

[jiminy-billy-bob]

Actually I think the rectangle light above the building is not invisible. I did that to avoid dropped shadows of the structure on the frosted glass (2sided material).
It is an artistic choice, it depends on what you want.

[FrankGehry]

Hi guys,

The setup described by jiminy-billy-bob is the right way to go.

It can still be optimized slightly:
- The exterior lighting can be done with a Sun & Sky. The 2-sided material should still work
- The big Area lights can be made slightly smaller and placed inside. They should be invisible and with their Affect Reflections and Affect Specular options disabled
This way you'll have some direct light in the interior, not relying 100% on the GI calculation.
It'll improve the quality of the lighting and should be faster to render (much lower GI quality will be required).

Regards,
Konstantin

I finally figured out what I think was the best approach. Below in the rendering. Inside the structure, you can see the softened light from the skylight above.