I'm trying to create a large-ish cave, similar to Blackreach (though probably quite a bit smaller). Since, following the way Blackreach was set up, I need terrain in my cells and therefore I can't really do it as an indoor cell, I'm trying to set-up a custom worldspace.

Now, as far as I can see, new worldspaces seem to have a bunch of issues in the CK, but mostly due to LODs and problems with the heightmap editor. As far as I can tell though, I shouldn't really need either of those - it's only a cave, so I don't urgently need any LOD meshes and I can do the terrain by hand...

...except that I can't get the Landscape Editing tool to work. I've got a whole bunch of black water in my new worldspace, but as much as I try to paint terrain onto it, nothing happens - it's just a flat, flat plane of water, with the brush impotently skating around the surface.

Has anyone gotten this work? Is there something I need to do before I can alter the terrain, or is this tied up into the other custom Worldspace issues?

not 100% sure but check default land height, water height, LOD water height and HD LOD Diffuse + HD LOD Normal need to be directed to Steam\SteamApps\common\skyrim\Data\textures\landscape\mountains\MountainSlab02.dds

You're trying to paint water?

More than likely the land height was lower than the water.. and the person may not know to hold left mouse button and move up/down to raise/lower the land.

Hah, the issue turned out to have been just as dumb - for some reason terrain was disabled in the View -> Show/Hide window, so it just wasn't rendering any terrain at all, and all I saw was water.