queuing rops (for local renders)

 it seems like chaining rops breaks a bit - the frame ranges don't seem to get respected.

It's better to use a merge rop & specify strict frame range

exporting alembics or fbx from houdini with transforms

 Didn't realise this...and wasted about half an hour figuring it out..
If you, for example, are using a FETCH node or a rivet and need to export an object with the transforms you can a) use the bake animation ROP (must be used in ROP context!) b) click File>export as FBX or Alembic.

For the latter to work, you must place your stuff into a SUBNETWORK, or it will not export correctly. VERY ANNOYING. It's a bit like putting things into a group before exporting an alembic in Maya, just much less obvious.

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..