This page provides information about the Refraction render channel in V-Ray for Blender.
Overview
The Refraction Render Channel stores refraction information calculated from materials – such as glass or water – that refract objects behind them in the camera's view. This means the brightness, coloration, etc., of the refractions can be adjusted without the need to re-render.
Any material in a scene with a value set for its Refraction parameter generates refraction information that can be seen in this render channel. A surface with no refraction values set in its material(s) contains no information in the render channel and, therefore, renders black.
The Refraction Render Channel is a key component in the main Beauty render and can easily be used to control the refractions in the Beauty composite.
The Refraction Render Channel itself is already a composite of the V-Ray Raw Refraction Render Channel multiplied by the V-Ray Refraction Filter Render Channel. When finer control over refractions is needed in the composite, add these additional two channels to the output along with the V-Ray Refraction Render Channel.
UI Path: ||V-Ray Node Editor|| > World > Render Channels > Beauty > V-Ray Refraction

Properties
See the Render Channels page to find out where you can find these properties.
Channel Name – Customizable name for the render channel.
Enable Deep Output – Specifies whether to include this render channel in deep images.
Color Mapping –
Consider For Anti-Aliasing – When enabled, anti-aliasing is used where possible.
Filtering – Applies an image filter to this channel.
Derive Raw Channels – Generates data in the raw channels by combining the respective color and the filter color channels.
Vfb Color Corrections – Applies the post-render color adjustments made from the VFB.
Denoise – Enables the render channel's denoising, provided the Denoiser is enabled.