# Shadows with matte objects and vray sky in CPU mode

**URL:** <https://forums.chaos.com/t/shadows-with-matte-objects-and-vray-sky-in-cpu-mode/104806>\
**Category:** Issues\
**Created:** [May 8, 2021, 6:38am UTC](https://forums.chaos.com/t/shadows-with-matte-objects-and-vray-sky-in-cpu-mode/104806 "2021-05-08T06:38:50Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![francomanko](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/francomanko/32/1722_2.png) [@francomanko](https://forums.chaos.com/u/francomanko)\
**Post date:** [May 8, 2021, 6:38am UTC](https://forums.chaos.com/t/shadows-with-matte-objects-and-vray-sky-in-cpu-mode/104806/1 "2021-05-08T06:38:50Z")

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Hi,

I was just messing around with getting shadows in the alpha using vrayobjectproperties and matte etc. I noticed that if you add a vray sky, in CPU mode the shadows are yellow (with default sky settings) . Disconnect the GI and its white. This doesnt happen in GPU, that renders white.

So couple of questions

1. Is this a bug  
2. If so, have I found a bug thats not GPU but instead CPU..and if so do I win a prize 😉

Ive attached a scene. Image shows the alpha channel with yellow shadow.

 ![yellow_shadow.jpg](https://europe1.discourse-cdn.com/chaosprd/original/3X/9/1/91ed60d18b6db63fe7374865231336504127d7c9.jpeg)  
[yellow\_shadows.zip](https://forums.chaos.com/uploads/short-url/AlxM8bdVl77RTuhC2eZCoiw4ytn.zip) (12.9 KB)

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<div class="post-metadata">

**Author:** ![hermit.crab](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/hermit.crab/32/46825_2.png) [@hermit.crab](https://forums.chaos.com/u/hermit.crab)\
**Post date:** [May 10, 2021, 3:40pm UTC](https://forums.chaos.com/t/shadows-with-matte-objects-and-vray-sky-in-cpu-mode/104806/2 "2021-05-10T15:40:33Z")

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It is normal. GI on mattes is not yet supported in V-Ray GPU, hence the difference. It happens with regular lights as well.

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<div class="post-metadata">

**Author:** ![francomanko](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/francomanko/32/1722_2.png) [@francomanko](https://forums.chaos.com/u/francomanko)\
**Post date:** [May 10, 2021, 8:12pm UTC](https://forums.chaos.com/t/shadows-with-matte-objects-and-vray-sky-in-cpu-mode/104806/3 "2021-05-10T20:12:58Z")

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ah ok, thx for info