If you are a compositor then you know the troubles that come with a tight deadline. Compositing and rendering digital images take forever and a day to finish! Enhancing the quality of the rendered images, creating seamless integration between elements and avoiding human error renders, these are just a few of the many factors that compositors should consider during filmmaking. Luckily, there are several tools that could shorten the compositing process without compromising the quality of the images. One such tool is Cryptomatte.

What is Cryptomatte?

Cryptomatte is an open source automated ID matte generator created by Jonah Friedman and Andy Jones at Psyop. The application generates ID mattes with support for motion blur, transparency, and depth of field by utilizing scene organizational information – names, object namespaces, material names, etc. – that are already available during render times.

Making minor adjustments in compositing is also much faster with Cryptomatte because it could extract matte and mask out specific elements in a scene. Apart from saving time during compositing, Cryptomatte also comes with reader plugins that are freely available for major compositing packages including:

  • The Foundry Nuke
  • Black magic Fusion
  • V-Ray
  • Houdini
  • Blender Cycles
  • RenderMan
  • Redshift
  • Clarisse
  • Arnold
  • Flame
  • After Effects

Cryptomatte is meant to become an open standard ecosystem wherein developers could create tools and plugins that integrates with the application. The idea behind Cryptomatte is to create a diverse ecosystem of renderers who could produce and decode Cryptomatte images and tools. Cryptomatte is licensed using the BSD 3-clause license. To know more about Cryptomatte, click here.

How to Use Mantra Renderer to Output Cryptomatte

Using mantra renderer in Houdini to output Cryptomatte is easy, here’s how:

Step 1: Select Mantra ROP then click Images > Cryptomatte.

Step 2: Click + next to Cryptomatte Layers to add a layer. Generate IDs by selecting the property. You can also choose the built-in properties from the dropdown menu or use Properties node to type in any user string property that’s added to objects or materials.

Cryptomatte
Photo Credit: sidefx.com

Step 3: You can set Different File to the name of the Cryptomatte you want to save and create OpenEXR files. If this path is not specified, the Cryptomatte layer will be stored with the primary output.

Cryptomatte
Photo Credit: sidefx.com

Step 4: Render.

Cryptomatte gives you the option to build custom properties, use the application alongside Houdini COP context, or use Crypto-node to pull mattes after rendering.

In the video tutorial below, Helge Maus of pixeltrain.de demonstrates how Cryptomatte is used within Houdini 16.5:

Basic Color Correction Using Cryptomatte

Using Cryptomatte for Instancing and Unique IDs

To matte a specific instance, you have to generate Cryptomatte using a user string property with value that is unique to each instance. Here’s how it’s done using Material Stylesheets:

Step 1: Set up instancing, use fast point instancing.

Step 2: Use Attribute Expression to give each point inside Instance node a unique integer.

Cryptomatte
Photo Credit: sidefx.com

Step 3: Add the user string property to the Instance node. Then, add a root level stylesheet, target Point Instances then using Inline Script, override script Render Property. Finally, set up the appropriate bindings.

Using Cryptomatte in Redshift

In a 2-part video tutorial, Saul Espinosa shows how to use Cryptomatte in Redshift renderer. The first part of the tutorial covers all the options that Crytomatte presents within Redshift renderer, including useful settings for enhancing 3D images:

Using Cryptomatte in Adobe Photoshop

In the second part of the video, Saul Espinosa shows us how to use the ID mattes extracted by Cryptomatte in Adobe Photoshop and other applications:

Using Cryptomatte in Blender 2.8

In this tutorial, Cryptomatte is used to mask out areas while compositing in Blender 2.8 cycles:

Using Cryptomatte In V-Ray for 3DS Max

Cryptomatte Tips and Tricks

Transparency and opacity are two different things. Transparent materials obstruct camera rays and cast secondary rays while partially opaque materials let camera rays through. You won’t be able to generate matte for objects behind transparent materials because the pixel coverage is calculated based on opacity.

Cryptomatte uses the primary plane’s pixel filter. You can use different custom pixel filter plugins except for filters that reads data from additional image planes.

Although Cryptomatte is the de-facto standard for ID mattes, it doesn’t have support for micropolygon rendering.

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