Cryptomatte

Cryptomatte is a method developed by Psyop for efficiently encoding accurate mattes. It typically uses three to five automatically generated render channels stored in a multichannel OpenEXR file which removes the hassle of creating dozens or hundreds of Multimattes. 

Compared to the Multi Matte Render Channel, Cryptomatte offers the following:

• It does not require a setup with object IDs, etc.
• Only requires a fixed number of additional render channels, typically four.
• It cannot be propagated through reflections or refractions.

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.

Id Type – Specifies how the ID mattes are determined.

Node Name – Creates mattes by node names.
Node Material Name – Creates mattes based on the materials in the scene.
Node Name with Hierarchy – Creates mattes by node names and takes the node hierarchy into account for linked or grouped objects.
Node User Attribute – Creates mattes from a property specified in the User Attribute field.
Node Asset/reference name –  Creates mattes based on Cinema 4D References made within the scene. Note: This does not create mattes based on Cinema 4D Assets, only file references.
Node Layer Name – Creates mattes based on the layer names in the scene.
Sub Object Name – Creates separate mattes for each individual object within a V-Ray Proxy when the proxy file contains more than one object. This option works by getting IDs from within the  V-Ray Proxy by creating a mask for each sub-object of the proxy (.abc and .vrmesh). This type produces masks for V-Ray Proxy objects only - regular geometry is not included in this cryptomatte layer.

User Attribute – Specifies a user-defined attribute for creating ID mattes when the ID type is set to V-Ray user attribute.

Add Root Object Name – When ID Type is set to Sub object name,  it specifies what information about the sub-object names goes into the Cryptomatte manifest. The dag path and the sub-object name(s) (e.g., MeshName.abc/ObjectName) are added to the manifest.

Number of Layers – Specifies the number of layers for the render channel, which determines the number of objects that can be distinguished per pixel. If multiple objects intersect at a single pixel, higher-order layers will contain non-zero results. The default value of 6 is normally enough for most cases.

Write Metadata – Determines whether or not the render channel saves the metadata.

Object Path Start Slash –