Most systems for automatic navigation inside a 3D virtual environment often require pre-decomposing the free space into some kind of uniform units or precalculating the path or road map. In this thesis, we propose a new technique for navigation through in a 3D virtual environment without lots of pre-calculation so that the system allows users change their interest target during the camera motion, and even allow users dynamically adjust the 3D objects inside the 3D virtual environment without too much recalculation involved. The technique has successfully been integrated in a system for walkthroughs in a 3D virtual environment.