The editor is used to create 3d stuff. It uses Constructive Solid Geometry approach. Thus the user has to deal with solids only - no need to worry about edges, vertices etc. A solid (another name is a brush) can be of any shape - as simple as a cube or as complex as a whole level. Solids can be moved, scaled, rotated, copied, pasted, saved and loaded. The main operations however are CSG Union, Substraction and Intersection.
This version of the editor runs under DOS (or DOS box in Win). If you do not have VESA 2.0 with linear framebuffer support loaded it will use standard 320x200x256 VGA mode. This mode is only good to get the fullscreen texture mapped priview in almost real time. If you install VESA 2.0 (UniVBE 5.1 or later) the editor runs in 640x480x256. Actually it can run at any resolution. Note that if you have VESA 2.0 without linear framebuffer, the editor will die.
Both mouse and keyboard has to be used. I decided against lots of menus for two reasons: keyboard commands are usually faster (when you know what to press of course), coding graphics menu interface under DOS takes time.
Some specs for those who do not want to download the editor :-)
Now some not so exciting info: The interface is far from being perfect (or finished), CSG, texture and light control is not 100% done... But this will change. I use straight-forward z-buffer with texture mapping but for simple scenes it is still real-time. Lighted preview is another matter. It is slow as the shadow maps are created on the fly for each poly.
Anywayz, you can take a look at the editor and its docs yourself. If you find a bug that is not mentioned in docs or just have some comments, please, feel free to send an email to firstname.lastname@example.org
Demo of Solid Editor (100K) - small download with a few textures and solids
Solid Editor (650K) - the editor + lots of textures + couple of solids
Source code (130K) - full source code
DOS4GW (144K) - if you do not have it, you can't run any exe's