Interior Lighting help

I downloaded this ancient file from Blendswap that uses blender internal render.

I’m trying to update it to use Cycles and I can’t figure out how to get the light on the curtains to be the same.

The curtains are translucent enough to actually be seen through… maybe they used transparency instead of mixing diffuse + translucent?

There’s also fairly well defined shadows being cast onto the floor from the window. There is a sun lamp in the original scene but with the translucent curtains in the way I’m not getting any shadow definition. What should I try to change?

2021-02-09 16_12_15

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Translucent material will generate always diffuse scattered light, if you want to have some of that light passing through the curtain you really should mix the transparent shader there. I would do it using a layer weight node or fresnel node together with the light path node to keep some impression of the curtain waves on the shadows.

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Correct. The translucent shader did not look as good as using transparent shader. I’m not sure exactly how I’m supposed to mix them together compared to your description.

My other problem was the sun lamp in the original scene had an angle value of 90 degrees resulting in no harsh shadows. I guess the creator made more changes to their file after uploading it to blendswap. Also the compositing after the render is a big reason why their preview image differs from what I’m seeing in the viewport.

I don’t understand why my viewport preview renders instantly but the final render spends 2 minutes preparing BVH things before it starts to actually render.


Hi, thinsoldier. In real world, the light is scattered in a situation like that. The way the light is coming inside the room, sounds very strange to me… You should use a translucent material, and increase the exposure value to get more light. This can be made using Exposure in Color Management or post production, in Compositor.

Maybe because of the particles from the mat on the floor.

The objective is to get something like this effect on the shadows, where the waves of the curtain can be seen.

Here is the setup to show the part you were not understanding:

Of course it needs some tweaks to adapt to your scene, but I believe it gives a more believable aspect to the filtered light through the curtains.

Setting the “Layer Weight” node blend value to 0.2:

The blur on the light of the sun you can achieve increasing the size of your sun disk.

Moving a bit the light source:

I definitely prefer your shadows on the floor but the curtains themselves are maybe a bit too transparent when viewed in the shadowed areas


vs what I had before:

I think mine is also too transparent but in a different way

What I sent to you was not the complete shader, it was only the part which was supposed to controll the shadows.

I will make a complete setup with the diffuse you used to show what it was supposed to be.

Thanks. Can’t wait to see. I mixed yours with a diffuse and I’m waiting for it to render now to see what it looks like.

I made a mistake on that. It will be better. I forgot to delete one mix there.

Here it is, after correcting my mistakes:

You can play a bit with the blend value of the layer weight to tweak for your scene.

the render I was waiting on earlier

Thanks. I’ll give it a try.

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For whatever it might be worth: the actual lighting does not have to be what it appears to be. In other words, you can “seek to actually implement” the lighting as it would actually be in real life, or you can: “Fake it, Ingrid.”

If you’ve got the horsepower, the time and the inclination, you can actually put that curtain there, make it “really translucent,” put a light behind it, put a floor down, and after some amount of time get the actual pattern of light that would show up on that floor, because you literally simulated real life.

Or you could first make the curtains of a material that “appears to be illuminated,” and use – say, some kind of “gel” in front of a spotlight to create a corresponding pattern on the floor. Is it “correct?” No it is not. Is it “plausible?” Yes.

Any news? How is the thing going?

Your last shader looked very similar to this one but more white in color

I decided to stick with your earlier shader that I then simply mixed with a diffuse.

I also just found that the same author had made a cycles version of this same scene so I’m going to check that one out and see how different my changes were from what they did.

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