Cryptomatte – One of my Favorite Features of V-Ray 3.6

Cryptomatte is a feature I have been waiting for for a long time.

I have been using V-Ray for a few years now and I have constantly been impressed with their updates.  Whether it’s added features and functions or faster render times, Chaos Group always delivers, and that is one main reason why I will most likely always use V-Ray in my work.  But there was a feature that I had been wanting for a long time.

Before V-Ray 3.6, I used the MultiMatte render element to help with post production workflow.  It was a bit tiresome to use for bigger scenes.  MultiMatte uses the RGB channels of an image to give you masks for selected objects.  Most of the time, I would have to sit and plan what I might need masks for and organize them appropriately. Since MultiMatte uses only 3 channels, I would most likely have numerous amounts of MultiMattes, and they were mainly a precaution (Certain objects in the Red channel, Green channel, and some in the Blue channel).  Cryptomatte gets rid of that workflow entirely.

With Cryptomatte, I’m able to have masks for everything with just one render element.  Since I use NUKE for most of my post work on animations, this is an easy choice.  Psyop worked with Chaos Group to create a script to run a Cryptomatte node in NUKE that will allow you to select one or more elements in your render to use as a mask.  It’s super easy too!

I did a quick test with a large scene to see how well it worked and how easy it was to use.  Here is the original, non-edited image:

This is an exterior scene for a client I created.  There are multiple angles and lots of objects.  Since this scene is so large, I like to have masks as a backup in case I notice something after I rendered all the images out, and they can take a long time to render.

This is my V-Ray panel in 3ds Max.  You can see I already have some MultiMatte elements set up.  I added a Cryptomatte element just to test it out.  A cool feature is the ability to adjust how to Cryptomatte is created.  In this example I choose to set it up using my scene material names.  This basically means it’ll create an element for each material.  This is extremely helpful and will allow for some nice organization in NUKE.  Here is what the Chaos Group documentation says about each id type:

“id type – Specifies how the ID mattes are determined.

Node name – Creates mattes by node names.
Node name with hierarchy – Creates mattes by node names and takes the node hierarchy into account for linked or grouped objects.
Node material name – Creates mattes based on the materials in the scene.
Node user property – Creates mattes from a property specified in the node user property field. 
Layer name – Creates mattes based on the layer names in the scene.”

Once I rendered out the image, I brought it into NUKE. (NOTE: I found out that Cryptomatte won’t work properly in NUKE if you save the image as an EXR from the V-Ray Frame Buffer.  It will currently only work if V-Ray automatically saves it from the render panel dialogue.) Once the NUKE node is installed, all you do is add the node to your work space and connect it to your read node. (To install the NUKE node for Cryptomatte, go to this link here.)  Here is what my Cryptomatte looks like in NUKE.

It may not look like much, and it may look like all the colors are pretty similar, but the Cryptomatte node in NUKE takes care of that.  There is a color picker in the node and when you CTRL+Click a color, it will highlight it perfectly, and when it’s highlighted, it’ll act like a mask.  Here is my simple NUKE comp.

Once you select your mask colors, this is what the Cryptomatte will look like:

You can easily tell that I’ve selected the trees.  With these trees selected, I can use the Cryptomatte as a mask, as you can see in my comp screenshot.  For the sake of research and demonstration, I just created a ColorCorrect node and adjusted the trees a bit.  This is strictly just to test and see how well the mask worked.  Here is a side by side of the original image and the edited image:

You can see all the trees are much more contrasted with the background and pop more.  The mask worked very well.  Since the trees and leaves get pretty small in the background, I did notice some masking issues with the sky surrounding the leaves being masked as well.  It’s very subtle and there are ways to fix this but I didn’t attempt it for this test.  My goal was to setup Cryptomatte and see if it worked how I imagined, and I am happy to say, it did.  Very well I might add.  I can now add Cryptomatte to all my renders and get that masking backup I like to have.  Chaos Group released a short video explaining this as well which you can watch right here:

If you are interested in Cryptomatte, you can check out the documentation here.  Also, check out our store for deals on V-Ray for 3ds Max and V-Ray for NUKE.  If anyone has any questions, ask it at http://answers.vray.us and a trained V-Ray specialist will help you out.  Thanks!