I'm working on the beginnings of a landscape tool and just started building the base in PDG.

I have one HDA that takes landscape as input and just passes it on as output. This HDA works in UE as expected by it self.
But when that same HDA is referred to in my PDG/TOPS, it outputs nothing (but an empty scene component).

I made an other HDA that takes in a string as input and creates a mesh out that text. This HDA works and can be updated with new input trough PDG, no issue at all.

When I open the unreal scene in Houdini (Houdini - Open Scene In Houdini) my landscape input is there. I also managed to output the incoming path, used by my Object Merge, as a mesh to Unreal. Reading - “/obj/valdemar_nyhlen_test_tops_hdap_refTerrain2_Merge/valdemar_nyhlen_test_tops_hdap_refTerrain2_Merge”

Any thoughts on what could be wrong or new ways to debug this?

Just found the issue:

In order to process ad-hoc geometry in PDG (as in: geometry from a SOP path that does not live on disk), use the TOPs "Geometry Import" node to fetch the geo from the SOP path. It will temporarily store the geo on disk and provide the necessary @pdg_output attrib for further processing in a subsequent HDA processor, for example.