I've simplified a larger setup that I'm working on with very large amounts of high res terrain tiles. I'm trying to use an invoke node to split the terrain in order to work with a single copy in memory. It doesn't look like my @pdg_index on the tile number is working. I've also tried to wedge it in there with both push and pull. The attribute updates and is visibly changing when I use the target override, but it just doesn't work when cooked. Is this a limitation or should I be doing this another way?

This is a limitation of Compiled Blocks in Houdini - it's currently not possible to use the @ operator to access SOP attributes or work item attributes. The current work around is to use the Geometry Import TOP node to Add a work item attribute onto the geometry, which can be done at the bottom of the parm interface on the Geometry Import. That provides a mechanism to transfer work item attributes in PDG/TOPs to the geometry itself, where you can then access them like any other geometry attribute using SOPs.

How exactly does the add attributes work? I'm trying to add @pdg_index as an attribute but it doesn't seem to work. There's no information in the documentation on this function.

Are the attributes added to every class on the geo or just the class specified in the source geometry section?