Branching patterns of shrubs etc

[Cyclops]

This is something I've been thinking about for a long time now. You see I see a lot of shrubs pruned each summer and then in winter you see all the branches going this way and that way-same with trees, but I got to wondering  if theres a mathematical formula that decides which branch goes where etc,just like how cracks in mud and glass always appear at certain angles from each other. Surely the placing of each branch twig and twiglet isnt just random? Then I thought, what about if you could say to the computer, show me all the branches pointing such and such a direction and eliminate the rest, or show the branches that emerge at a certain angle from the main primary branch etc. Are there such programs out there?
~Then I saw sonething in a link posted on here called Diffusion Limited Aggregation and I saw these 3D examples http://local.wasp.uwa.edu.au/~pbourke/fractals/dla3d/ and that me think thats kind of what I've been thinking about all these years!