Ok, I tested the multilevel release on windows r5 a bit, it generally works. FPS impact is noticeable if theres actually additional levels drawn (so if your current screen spans across levels, fps will drop. multilevel 15 is very resource intensive. The FPS in the fort I tested it in were bad to begin with though. And it looks very nice.
For me, mapshot produces a very corrupt image (the game zooms out correctly for a second to encompass the entire map, but the .tga file looks like a completely distorted broadcast image or sth like that. Screen:
http://i.imgur.com/svQyKzF.jpgAt the very bottom you can see a road I built into the mountain, and which is actually there, so it is actually doing something right... very weird
When I went up to a z-level in the sky where no layers would be rendered at all, Dwarf Fortress crashed.
That's it for now. Generally very nice, the main functionality is working nicely^^
Massive optimization idea: I am very bad at coding and what I say now is probably nonsense, BUT: as far as I understand how this works is that you look at the game memory to where what should be and then tell the renderer to render something different than it normally would. Now my idea: Would it be in anyway possible to take that same information from memory, replace it with basically NOTHING and instead use an external executable for rendering? So you make an executable which displays what should be rendered, it would look exactly like being rendered in DF itself, all input would be relegated to the df main executable. The advantage of this would be that the OS would automatically assign this second executable it's own cpu thread/core. And if you replace whatever DFs rendering should show with nothing, that should free up a LOT of cpu for the main exe to do other stuff (pathfinding etc), in theory drastically boosting FPS.
At least the part where you just replace all rendering with nothing/black squares should be somewhat easily testable just to look how much FPS would increase if rendering would not be done on the same cpu core.