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Arthur Araqelyan avatar image
Arthur Araqelyan asked ·

How can i light an object (f.e. closed cube) from inside and outside? C4D

Hello ....i'm experimenting with lights in cinema 4d and i found that i can't light an object from inside and outside at the same time ...i assigned a SSS material to the object..it's a cube for me in this example...and i want to apply the light form inside, so i placed it there....but it's just show me black color after rendering....so i just reversed the normals for my cube...and it starts work....but after i tried to apply another light from outside ....but because i reversed the normals i don't see the effect oof outer light... so i can't see 2 effects at the same time from 2 light sources where 1st one is placed inside of my object and 2nd one outside.....I don't want to do this with full closed object ...like a sphere or cube or something else which doesn't have an open polygones ...so it this possible to do with arnold lights?

1. this is normal state of object ...non reversed normals ...and and we can see outer light

2. this is version with reversed normals ...to see the effect of inner light

but in this case we don't see the light of our outer source...i turned off inner light ...and i can see only small red specular)))

renderc4dtoalight
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Lee Griggs avatar image
Lee Griggs answered ·

I enabled Thin Wall in that scene and got this. The normals (pointing outwards) look correct to me.


thin-walled.jpg (61.1 KiB)
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Arthur Araqelyan avatar image
Arthur Araqelyan answered ·

Yessss that's it!!! Great!!! Thanks Lee!!! :D ....thin wall!! You're absolutely amazing!)))

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Giuseppe Schiralli avatar image
Giuseppe Schiralli answered ·

I'm not sure it's realistic. If the cube is opaque, the light from inside would be not visible from outside. I'd try to create a material for the cube that is sempi-opaque, that allows lights from inside to come out, and vice-versa.

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Giuseppe Schiralli it's more then realistic)))) ....it's not about opacity ....it's SSS ...just try to put your finger on your phone's flash and turn it on ....i don't think your finger has an opacity)))) ...but you see yes what's happening?)) ..just imaging you put the flash light inside of your finger...this is what i wanted to see))

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Arthur Araqelyan avatar image
Arthur Araqelyan answered ·
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Arthur Araqelyan avatar image
Arthur Araqelyan answered ·

Lee Grigg first of all thanks a lot for answers)) ...the 1st one is actually a specular, if we'll turn the specular off, we won't see that red light ...but the second way works actually :) ...i liked, but i noticed here something....it works only when the normals of our cube polygons are reversed...but in normal state i doesn't work ....take a look at this screenshot..here the polygones has default normals direction...they look outside...this is the state when we create a cube

and in this case when i'll render, it won't show our inner light..but here we still have this small SSS value(0.1) which works with reversed normals...look

soo to get the result we wanna get we need to reverse our normals ....ok it's not hard to do))) ...but why it doesn't work with default normals direction?)


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Lee Griggs avatar image
Lee Griggs answered ·

Reducing SSS reveals both (with thin wall and normals pointing outwards).


sss.jpg (184.8 KiB)
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Lee Griggs avatar image
Lee Griggs answered ·

Increasing the Exposure reveals the red light.


exposure.jpg (106.9 KiB)
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Arthur Araqelyan answered ·
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Lee Griggs answered ·

Could you upload the scene, please?

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Arthur Araqelyan answered ·

i just tried.....it doesn't help) ....i don't think it could help ....this node just allow to set different materials for sides...but by default ...normal material it anyways applied for both sides

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