Tree Generator is based on some simple algorithms to create realistic trees : Each branch has a certain number of children branches which are rotated from a certain angle from their parent, which are scaled (reduced) and translated (along their parent direction), with bending, twisting ... and this is processed as many times we'd like (here, limited to 10 times ... but that's enough for a very good looking tree).
Once the tree is created, you can export it (DXF, 3DS and OBJ formats) and use it in most of 3D softwares (ALL Autodesk ones : Autocad, 3DSMax...and lots of other softwares), or create billboards to reduce the tree complexity. | 
