I am writing a system which keeps track of asset metadata within the runtime. It relies on the FS_Helper classes to look up asset locations based on a uri scheme. I would like write data to the hip file on save and fetch it out of the hip file on load. Is this possible via the api?

Traditionally, asset management systems install things like menu hooks and/or expose web interfaces within Houdini's web browser. This allows one to run scripts to create nodes and persist data in the scene file via the created nodes (eg. userdata [sidefx.com]).

Having said that, there are various ways to hack it. One of which is to store scene level “global” variables. eg. OPgetDirector()->getCommandManager()->setVariable(). OPgetDirector() gives pointer for the root “/” scene node. So you could also store userdata there as well (you can call into the Python HOM API from C++).

Thanks for the suggestions. One more thing; is there a way to register on-save and on open callbacks in c++?

No, which is also why having custom nodes in the scene might be a good idea.

That is too bad. I noticed

OP_Director
….
void setSaveCallback (SaveCallback cb, void *cb_data)
void removeSaveCallback (SaveCallback cb, void *cb_data)

and was hopeful that this capability existed via the HDK. What is the SaveCallback used for?

Ah, sorry. There's setSaveCallback() but there's no callback for open.

Oops, spoke too soon. Try OP_Director::addEventCallback().