This Instructable will teach you how to create generative objects with Processing code that can be 3d printed. One of the delights of using generative code to print things is that you can randomize certain elements so that every time you render a piece, it's completely unique. I was heavily inspired by the jewelry of Nervous System, which demonstrates this concept beautifully.
If you've never used Processing before, it may be helpful to look at a beginner tutorial first.
You will be using:
*There is a newer version now, Mk2 (however, the code in this tutorial was written before it came out and only works with the original Modelbuilder)
BTW, I'm using a Mac, but you should be able to do it with Windows and Linux too.
You should also grab Modelbuilder's source code from Github. In the modelbuilder master folder, navigate to export > Modelbuilder v0007a03. The folder inside there, called modelbuilder, is what you should move into your Processing libraries folder.
Once you've got everything in the right place, open Processing and create a new sketch.
The code here shows the basics of what you need to initiate your model object and bring up a blank canvas. If it throws and error on the first line, make sure your ModelBuilder library is in the right place, and that within it, the 'unlekker' folder exists inside of 'src'.