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Rémi Sello avatar image
Rémi Sello asked ·

How to get Arnold to cast shadows on tranmissive glass objects ?

Hello everyone,I'm running into a big problem on a project where i need to render glass objects with moving shadows.The problem being : i can't seem to get any shadows from a glass material !

Tried :

  • Opaque ON/OFF (does nothing)
  • Lowering transmission a bit (start to create shadows but not strongly enough and we loose quickly the glass so not an option at all)
  • trying all light types
  • C4DtoA and also MtoA : same result

I've come across a few tutorials where there is indeed shadows being casted (eg :https://www.youtube.com/watch?v=QYmq_cSb5Mg ) But opening this scene or trying to replicate it doesn't produce anything.

Can somebody point me in the right direction or should i simply switch render engine for this job ?

best


transmissionglassshadows
glass-no-shadows.png (864.9 KiB)
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Stephen Blair avatar image
Stephen Blair answered ·

Another way is to use a rayswitch (to get around "smart opaque") and use opacity / caustics for the shadow


c4dtoa-glass.png (444.0 KiB)
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Lee Griggs avatar image
Lee Griggs answered ·

No need to change render engines. Just reduce the Transmission Weight so that it is not fully 1.


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Lee Griggs avatar image
Lee Griggs answered ·

Did you try any of the above suggestions? Can you upload a simples scene somewhere?

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Rico Hofmann avatar image
Rico Hofmann answered ·

In older versions of Arnold ther was a shadow. Now the opake switch is set automatically if you have a transparent object. I think it would be helpful to have the option to acticate the old behavior.

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Sébaste Thifault avatar image
Sébaste Thifault answered ·

You can leave the transmission to 1 and use transmission depth instead and some scatter, it will give you more realistic shadows.

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Rémi Sello avatar image
Rémi Sello answered ·

Hi Lee,

Thanks for the reply but that was my second point in the list : the shadow produced when reducing the transmission to 0.9ish is not realistic, it's just a "faded" shadow. So not a good work around for me sadly :(


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Can you upload the scene somewhere?

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