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I'm relatively new to blender and I'm trying to make a solar system inside a sort of snow globe, is there any way to make it so that light from outside the globe doesn't come into it? I'm trying to make the outside be white and the inside be dark without making the glass darker so it doesn't make the planets darker, is there any way to do this?

blender 2.92.0

cycles

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  • $\begingroup$ Are you using Cycles or EEVEE? $\endgroup$ Commented Feb 17, 2022 at 1:58
  • $\begingroup$ @ChristopherBennett I'm using cycles $\endgroup$
    – fox
    Commented Feb 17, 2022 at 2:05
  • $\begingroup$ Sorry, i'm trying to figure this out here. You say you don't want light coming in, but you also don't want the planets to be dark - where are the planets being lit from? $\endgroup$ Commented Feb 17, 2022 at 2:18
  • $\begingroup$ @ChristopherBennett they would be lit by the sun in the middle. when i said I didn't want the planets to be dark I meant that I didn't want to darken the glass $\endgroup$
    – fox
    Commented Feb 17, 2022 at 2:21
  • $\begingroup$ I've added a comparison image to my answer, maybe this helps to see the differences in the setup. $\endgroup$ Commented Feb 17, 2022 at 11:54

2 Answers 2

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Try something like this - the refraction might suffer slightly, but overall it should perform as expected:

Light

Here it is beside an identical setup, only with a plain glass shader. You can see the "modded" one is a little darker, but that could be attributed to "light not getting in". It still looks rather realistic, I would say:

Light2

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  • $\begingroup$ I don't get it... I've made a comparison between my and your node setup, and although I suspected mine would be brighter than yours, I don't understand why it looks sooo dark when I've set it up. How bright is your environment? And the sun? $\endgroup$ Commented Feb 17, 2022 at 12:16
  • $\begingroup$ ...I know you've just made it a solid glass ball whereas I made a glass material with a thickness so that the refractions look different in our answers, but I've checked that, it doesn't help with the brightness. $\endgroup$ Commented Feb 17, 2022 at 12:24
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This is my node setup. It is quite simple and makes the reflections on the snow globe a little darker as if I were using only a regular Glass BSDF, but still it looks okay I think. I mix the Glass BSDF with a Diffuse BSDF set to black (so that the diffuse doesn't reflect light on the planets), as mix factor I use the Is Reflection Ray output of the Light Path node.

On the left, the sun and planets are in open space to see how they would actually be lit by the environment. On the right you can see the planets are dark where they don't get light from the central sun sphere.

snow globe material

To show this a bit better, I delete the central sun so that there could only be light from the environment falling into the globe, but it doesn't.

environment lighting

This also works if there is a bright point light outside the globe (I've taken down the environment to focus on other light sources):

point light

And of course with other light sources like sun, spot or area light as well.

area light

By the way, here is a comparison so you can see how the different node setups in Christopher's and my answer work out using my "snow globe scene":

comparison

Another difference between the setups is, with my setup the planets inside the globe get reflections on the glass inside, whereas they are not reflected in the other setup. But Christopher's node setup let's light from the sun shine on objects on the outside (at least when you make it very, very bright), but my setup doesn't let any light shine through to the outside.

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