- add more element icons. now element icons is not problem.
- change icon load strategy. now icon is loaded outside plugin. this operations might slow down blender but now I can apply my custom map to some operators to get better using experience.
- use new element icons to decorate some group name to let user know what this group stands for.
- add edit mode switch before bm export to prevent potential error
- let the default value of ZBuffer in Virtools Material become True
- fix the issue that duplicated elements adder do not understand enable option.
- add tunnel section creation and re-organise rail creation menu.
- allow duplicated elements (Nong xxx) creation for some special, such as Fan and Extra Point.
