Anyway, I've been re-building the heightmap editor using Urho3D. The forum thread where I show stuff is here, and the github repo for the project is here. It requires the Urho3D library to be built with Lua support, and so far the shaders I have written are HLSL only. GLSL shaders are on the TODO list.
The editor allows simple brush-based editing of height and up to 8 terrain layers. I've been experimenting with various shader schemes, starting with Urho's 3-layer scheme and elaborating up until I have settled on the current scheme: 8 terrain layers stored in 2 composite 4x4 texture atlases and a blending approach that uses the scheme described in this article. The results are quite nice:
The editor supports a rudimentary filter script system, wherein you can write scripts in Lua that apply effects or alterations to the terrain. Included filters so far include a basic Perlin fractal height generator, a Perlin fractal terrain layering generator, a river builder tool, a road builder tool, a tool to turn slopes greater than a specified threshold to cliffs, and so forth.
The UI is very rough. I am not in a polish stage on it yet, so things are barely usable. But I am working on it pretty steadily as I can. I'm getting to the point where I can start cleaning things up, though I am sort of waiting on some pending merges to the Urho3D master regarding shader structure before I really commit to a lot of the cleanup.
Anyway, that's about all I've been up to. I did dig out the Goblinson Crusoe code and attempt to build it against the latest master, but all I get is a black screen so clearly there is going to be some refactoring there if/when I ever get back to that game.