LDPartEditor will also support CSG.
Here are screenshots from the first implementation draft:
A "union" with a cube and a sphere:
https://lh3.googleusercontent.com/-vo20S...csg_v2.png
A cube "minus" a sphere and its intersection with another sphere:
https://lh6.googleusercontent.com/-YZk9r...g_v2_2.png
RESULTS of the final implementation
Here are screenshots from the first implementation draft:
A "union" with a cube and a sphere:
https://lh3.googleusercontent.com/-vo20S...csg_v2.png
A cube "minus" a sphere and its intersection with another sphere:
https://lh6.googleusercontent.com/-YZk9r...g_v2_2.png
RESULTS of the final implementation