Google SketchUp for Game Design: Beginners Guide by Robin de Jongh

The book takes a clear, step-by-step approach to building a complete game level using SketchUp with many props and textures. This book is designed for anyone who wants to create entire 3D worlds in freely available game engines such as Unity 3D, CryEngine, Ogre, Panda3D, Unreal Engine, and Blender Game Engine. It also targets all those who wish to create new levels and assets to sell in game asset stores or use in visualization or animation.