# GPU - Shadow Catcher

**URL:** <https://forums.chaos.com/t/gpu-shadow-catcher/102543>\
**Category:** Requests\
**Created:** [January 6, 2021, 2:50pm UTC](https://forums.chaos.com/t/gpu-shadow-catcher/102543 "2021-01-06T14:50:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![John\_Do](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/john_do/32/62862_2.png) [@John\_Do](https://forums.chaos.com/u/John_Do)\
**Post date:** [January 6, 2021, 2:50pm UTC](https://forums.chaos.com/t/gpu-shadow-catcher/102543/1 "2021-01-06T14:50:03Z")

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Hi,

I have a scene with a shadow catcher and it doesn’t work in GPU mode, as visible in the docs.

I’m surprised since it did work in the other V-ray integration I’m using ( V-Ray for Modo ), which is older. So I guess it’s not a core issue ?

Thanks,

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**Author:** ![shaio](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/shaio/32/36276_2.png) [@shaio](https://forums.chaos.com/u/shaio)\
**Post date:** [January 30, 2021, 11:34am UTC](https://forums.chaos.com/t/gpu-shadow-catcher/102543/2 "2021-01-30T11:34:54Z")

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For the shadow catcher to work on V-Ray GPU you need to have the “Alpha Contribution” set to **-1** under the Matte tab in the Object Properties tab. If this isn’t the case then we’ll have to check if it isn’t a bug. I’ll make sure to add this in the documentation as well.

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<div class="post-metadata">

**Author:** ![John\_Do](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/john_do/32/62862_2.png) [@John\_Do](https://forums.chaos.com/u/John_Do)\
**Post date:** [January 31, 2021, 10:09am UTC](https://forums.chaos.com/t/gpu-shadow-catcher/102543/3 "2021-01-31T10:09:05Z")

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Hi @shaio ,

I don’t have access to V-Ray anymore but I’m pretty sure it was a bug since it worked as expected in CPU with the correct setup.