Here’s a program that makes rocks in DXF format. They are kind of puffy, so you have to Alt S them a bit, and decimate them, and do some minor modifications, but it’s alot faster than making a complex rock from scratch. There is one for mac and one for windows. Free.
<edit> I fooled around with it some more, and you actually have alot of control over the ammount of vertices used, so you don’t have to decimate it, but you do have to remove doubles. Pretty cool if you are making a bunch of rocks.
http://www.laffeycomputer.com/macrock.html
Thanks for the post.
We should have a rock generator script built into Blender.
Technically we do, in World forge, which can make anything from a pebble to a planet, but it’s a slightly more intensive process than PCRock maker. 