Here's a great way to model flat edge rocks.



1.) Draw irregular polygon shapes on each of the 3 axes (I used three 5-sided shapes).
2.) Select all three closed shapes and run the boolean merge command.
3.) Delete all the extraneous parts and you're left with a rock shape.

It's hard to control with any artistic eye, but the results are very easy to produce.

I found that you can "find your groove" when doing this process and make oblong rocks or whatever.

I'd imagine you could make the rock more "shale-like" if you change the lines to slight concave curves.
A "tumbled rock" look could be achieved with convex curves.

Nothing beats the SubD process for boulders and round river rock though.

Note: I should mention that Pilou made me aware of this way of modelling. He's a genius!

-- Cody