Ive been given a CG multichannel render and I cant get anything to do with cryptomatte to work or do anything. Is there a good idiots guide to the built in Node? Or do people still use a Matchbox? ive tried following different tips from other posts and cant get a single matte of any kind
On the Youtube Flame Learning Channel there’s the official tutorial for the Cryptomatte node.
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It should be fairly straightforward as long as the cryptomattes that you’ve received are set up properly. Lots of different properties can be turned into cryptos. It could be individual objects, faces of a geometry, textures, or manually/randomly assigned among others. Often times you’ll receive two sets of cryptos, say objects and textures. This would allow you to isolate a specific object and a specific texture in different cryptomatte nodes and then combine the resulting mattes in a comp node. Sometimes you’ll receive crpytomattes where the assignments aren’t useful because the artist hasn’t broken them out properly.
As an example, say you have a swarm of bugs. There may be hundreds of individual bugs. You might receive a crypto where each bug is in a unique crypto, but this could quickly become tedious and overly complicated if you want to select half of the bugs at random. To help with this, the cg artist might give you two sets of cryptos. One separates the bugs by type, say bees and flies. The other would divide the bugs into two sets at random, say green and red. You can then select all the bees in one and then separate the bees into two sets using the additional cryptos. If the artist hasn’t set this up properly though you may find that all the bees and flies are in the same crypto. Everything will appear in one channel and it may seem as if something is going wrong in Flame when in reality you’ve received cryptos that aren’t particularly useful.
As far as setting it up goes, there will be four channels in your EXR that need to be fed into the node. The first will be just a front and the rest will have a front and matte. Attach them to the inputs of the node in descending order. Then look at the F1 view of the cryptomatte node. This will show you the combined channels in a format that is more visibly legible. Hit the add button and select the object that you want. It will appear in the node list and then you can select which matte output the object is added to.
It is possible that your viewing rules are interfering with seeing the crypto objects clearly. It may be helpful to bypass them entirely in order to see all of the objects.
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You might want to assume it is the fault at the CG end and grab yourself a sample file that is guaranteed to work for you:
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I have had Cryptomattes from Redshift that didn’t work in Flame. Not all the time, it seemed to be randomly happening. I was able to use them just fine in Nuke. If you have access to Nuke you could bring them in there and render out the mattes you need.
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