[Therion] extended profile preview idea

[Vasily Vl. Suhachev]

Hello

I am working on project with large profile and using XVI for preview 
result during editing "extend" commands. But it is very slow!

XTherion hanged a minute on each load of XVI file, on each zoom-in or 
zoom-out. And XTherion can't zoom out less then 25%, so I can't browse 
overall picture

Generating pdf with centerline is not an option too (station lines and 
labels overlapped each over, time assumed equally to XVI+XTherion)

Hence, it would be useful implement new mode for "export model" command 
for export extended profile as a 3d or lox model. Such behavior have 
extend.exe from Survex

-- 
  WBR, Vasily