I'd suggest digging around the Trainz community to find what converters have been written, if any. .dem is pretty obscure when it comes to the game modelling community so I'm thinking someone must have written something.
I've bumped into others as well over the years on my travels but I can't recall their names. I don't know if they'd do the job. I use Global Mapper which, in terms of supported formats sits nicely between GIS and terrain modellers (which essentially is your problem here). That supports pretty much everything. So you're looking at buying WM 2 Standard. If you look at the feature comparison chart you can see that 2 Standard has all the import/export formats that 2 Pro has. I would output as terragen or .bt and find another software to convert from that to .dem.
Thank you. However, height output nodes are available in WM 2, and I am talking about WM 1.25. As my worlds are mostly bigger than what is allowed in the Basic Edition, I would have to buy the Standard Edition at least, which I do not (yet) want to do before I am truly familiar with WM at all. Otherwise, I would indeed prefer the Microdem .dem format. If WM 1.25 cannot do that then I would like to know about converters that can convert WM outputs, preferably in 16+ bits precision, to .dem.
I have found lots of posts about importing dems into WM. I want to use my creations (as soon as I have one) as input for a fictional layout in the Trainz railroad simulator, of which I am very fond, and which I have been using since Day 1 (somewhen in 2001). There are programs to make Trainz terrains out of dems, but I am looking for the missing link. So I want to go the other way, meaning exporting terrains as dems. I have the feeling that this is already possible with V1.25 Standard Edition, which is the WM version I have. Perhaps I am not familiar enough with the terminology, as English is not my native language (it's German). Any suggestions?