DXTBmp only handles 2D textures I`m afraid
3D textures are different internally and if you edit with DXTBmp I suspect the output will be a 2D texture that won`t work the way expected.
I assume that by 3D you mean "cube map" as this is a DDS option that is available... just not in DXTBmp. I haven`t yet had the need to look into how cube maps work.
No problem, for me this editor is good enough to use it.
I noticed that some textures that i wanted to edit are linked with 3D objects. I could make 2D texture transparent (using Alpha Channel ), but 3D not.
Unfortunately, the only 3D editor that opens this particular type of model ( Ulitmate Unwrap 3D ) costs 59$ for full version with save changes possibility. I had a demo of this editor and i must say that it is awesome.
I' m a student from Poland by the way.
I 'm not skilled in 2D editing ,but your editor is easy to handle.