cryptomatte arnold houdini

 

I always forget how to do cryptomattes in Arnold & Houdini

cryptomatte AOV with arnold/HTOA

Another simple thing, which I always forget.

The most common crypto attribute I use is crypto_asset.
It seems to work best assigned at primitive level. So - in a primitive wrangle for example -

s@crypto_asset="poop"+itoa(@primnum);


The next part is to create an Arnold Shader Network, call it something like "CRYPTO"
Inside this, make an AOV Output  node. Create a cryptomatte node and hook this up to the aov_shader input. You may need to create a user_data_string with "crypto_asset" and plug that into the "crypto_asset" input of the cryptomatte node.


The last bit, is in the Arnold ROP you're using. In the AOV section, where it says "AOV Shaders", point it to they CRYPTO shop you made earlier -  /shop/CRYPTO

then add a new AOV and select "crypto_asset" from the list.

Hopefully this works!

Crypto_object is used when things are in different Houdini Objects... it isn't something that I usually do though..