---
title: "Alpha"
canonical: "https://documentation.chaos.com/space/VRAYHOUDINI/113280717/Alpha"
format: markdown
---
The Alpha channel is a grayscale image that stores the transparency of objects in the scene.



## **Overview**

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## **Attributes**

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## **Common Uses**

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The **Alpha channel** is primarily used as a mask to enable other elements to be placed behind the Beauty composite, such as the [Background ](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279766)Render Element. The Alpha channel shown below takes into account the transparency of the glass in the windows and masks them. See how the render looks before and after compositing.



## **Notes**

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- When using transparent materials such as glass, make sure that the material is set up to treat the material as transparent with regard to the Alpha channel. For example, when using [V-Ray Material ](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279382)as the material, set the **Affect channels** parameter for both Reflection and Refraction to **Color+alpha **or** All channels**. Otherwise, the transparent surface will not be treated as transparent in the Alpha Render Element.