If you're an Autodesk Maya user and you're looking to create rocks, boulders or rock walls, check out this excellent 7 part tutorial and learn how it's done. Maya is a massive 3D creation tool with so many aspects it's really mind blowing. This tutorial will help you improve your skills for your game building or just for you own art.
This tutorial will get into sculpting, retopologizing and texturing.
This tutorial uses Autodesk Maya, Mudbox, Adobe Photoshop and Xnormal, so if you wish to work along with the video, you'll want to have all those programs loaded up and ready to go.