I'm working on a Unity project that has a large map with multiple terrain tiles, and I'd like to process all tiles at once with an HDA.

I tried connecting to a Houdini SessionSync and importing with an input node, but that caused all tiles to pile together even with Using World Transform on. If I use multiple input nodes (one for each terrain tile) and merge the Heightfields, the baked output contains only the first heightfield/terrain tile.

Is there a way to import multiple terrain tiles from Unity, process them as one single Heightfield, and then split them up to import back into Unity?

In this tutorial [www.sidefx.com] (video 10 on the page) he splits the terrain into tiles using Heightfield tile split in the HDA and passes in the tile number in via the TOP (task operator). HDA processor no longer has iterations parameter so you use a generic generator in front of the HDA processor, checking "Copy Inputs to Outputs" and entering a value for Item Count (the number of tiles). In the HDA parameters of the HDA processor you pass in the tile number using @pdg_index. Sometimes when stuff comes into Unity you have to rotate the mesh by 90 degrees around the Y axis. I had to rotate each of my tiles.

If you don't want to use TOPs you could have multiple Heightfield tile split nodes and specify a different tile number for each one and then merge them - example [www.sidefx.com]. With this approach it comes into Unity as one mesh and I wasn't able to rotate each tile individually.

TOP:

Generic generator (genericgenerator1):

HDA processor for HDA that splits the terrain (HE_OUT_terrain_split):

But how about scatter points?