Reconciling scene realism with interactivity has emerged as one of the most important areas in making virtual reality feasible for large-scale mechanical CAD datasets consisting of several millions of primitives. This paper surveys our research and related work for achieving interactivity without sacrificing realism in virtual reality walkthroughs and flythroughs of polygonal CAD datasets. We outline our recent work on efficient generation of triangle strips from polygonal models that takes advantage of compression of connectivity information. This results in substantial savings in rendering, transmission, and storage. We outline our work on genus-reducing simplifications as well as real-time view-dependent simplifications that allow on-the-fly selection amongst multiple levels of detail, based upon lighting and viewing parameters. Our method allows multiple levels of detail to coexist on the same object at different regions and to merge seamlessly without any cracks or shading artifacts. We also present an overview of our work on hardware-assisted image-based rendering that allows interactive exploration of computer-generated scenes.