knew I had the links, here you go:
https://www.vision.ee.ethz.ch/~pmuell...gine/Documents
(documentation on procedural city, building and facade generation)
https://www.introversion.co.uk/blog/archive.php
Look at the 'Its all in your head' threads as it shows the development of a procedural city generator for a new game called subversion
https://algorithmicbotany.org/papers/#abop
Free downloadable book on L-systems written by the guy who developed it, Lindenmeyer.
I think that the paintfx tool also uses a variation of this for creating differing random plants.
Simon