this is a little routine I cooked up that makes an attempt at a branch filling algorithm I found on this website http://algorithmicbotany.org/papers/#abop 

Here's the source in txt: abush.txt

 and in .LSP: abush.LSP

 It takes about 30 seconds to generate a tree with a depth of six.  This code should also run without AutoCAD if the (drawbranch point1 point2)  function was reimplemented.

Run the program by calling (abush depth, branch) in AutoCAD after loading the LSP file.  Depth is the number of "recursions" (I Used mostly loops instead)  and Branch is the size of a child branch relative to the parent.

It takes a long time to generate these as it is O(2^8n) where n is depth. 

Here's a cad drawing generated with (abush 4 0.33) squaretree.dwg 

To load this program into autocad, type _appload at the command line,  then select Lisp as the filetype and find abush.LSP. then run the file with (abush 4 0.44) 

this displays the basic pattern at a depth of 2: 

Depth of seven isometric view  (took about 5 minutes)

top view

less dense versions