General improvements

It has been updated to work with the latest OGRE version.
It now requires C++11.
The platform compatibility has been improved. It works on Windows
and Linux.
The documentation has been improved and updated.
OIS has been replaced by Qt input.
The configuration files which used some custom format have been
converted to JSON.
Support for OpenEXR has been added.
The original Visual Studio project files have been replaced by a
CMake build system.
The source code has been formatted and normalized to UNIX-style line
endings.
Much unnecessary/old code has been removed.
Many improvements to the code quality/structure have been made.
Many small improvements have been made.
The use of the shaders has been improved.

UI improvements

The editor has been ported from wxWidgets to Qt.
Many dialogs have been re-implemented using Qt.
A brush settings widget has been added which lets one change the
brush size and related settings by a slider.
A startup settings dialog has been added which lets one change the
terrain size and related settings easily.
A button definition dialog has been added which lets one change
shortcuts easily.