CAMotics is a well developed gCode simulator that offers a wealth of highly useful features including cutsurface simulation, gCode editing and .STL export.
Simulations benefit from many options for display of toolpath, surface, stock and tooling. User projects can combine multiple processes and custom tooltables, for sophisticated and informative simulations. A wide variety of dynamic feedback in respect of job progress is available.
A builtin ASCII editor allows fast access to any project gCode file. Tabbed management of multiple files is very helpful. Changes within the gCode are monitored with automatic reminders regarding saving edited files. One of CAMotics most useful features is extraction of a 3D .STL surface using only gCode and tooling data.
The example nc files that come with the software demonstrate simulation and construction of many different types of 3D surface,, they are well worth a look. Good documentation and support are available.
Download Link: http://camotics.org/download.html
Hope it helps
Danny