The Material ID Render Channel isolates objects with specific materials by Material ID for compositing purposes. This render channel provides a mask for individual objects and materials that is easy to select in compositing software.

This render channel either shows each material (by Material ID) as a solid unshaded color or stores the Material IDs as integer values within the EXR format or VRay Image Format file. 

The Color (with Anti-Aliasing) method supports antialiasing at the edges of objects where they meet other objects or the background. The Integer (no Anti-Aliasing) method, which assigns a Material ID to each pixel in the render channel, does not support antialiasing as each pixel can have only a single Material ID assigned to it.

More than one Material ID render channel can be used if desired, for example, if you wish to have both solid-shaded color and integer-based render channels for maximum flexibility during compositing.

UI Path: ||V-Ray Node Editor|| > World > Render Channels > Matte > V-Ray Material ID

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.

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.