The Multi Matte ID Render Channel provides a mask for individual objects and/or materials based on the Multi Matte IDs.

The Multi Matte ID Render Channel contains no shading information at all; it only contains blocks of color that correspond to each Multi Matte ID. It uses the Multi Matte ID option available in the materials' properties.

UI Path: ||V-Ray Node Editor|| > World > Render Channels > Matte > V-Ray Multi Matte 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 – Includes this render element in deep images.