How can we expect computer graphics and interactive graphics methods to help attain these goals? The real power of computer graphics lies in its ability to accurately represent objects for which physical models are difficult or impossible to build, combined with its ability to allow the user to interact with simulated worlds. To understand how significant these features are, consider this: our entire common-sense knowledge of the physical world exists only in our mental models - we have watched and interacted with the immensely complex laws of physics governing such objects as water, sand, and trees, and have developed, through interaction, a mental picture that enables us to predict with some accuracy what is physically reasonable. Successful systems should include the capability of exploiting old models - creating pictures of unknown domains that exploit our existing mental models and perceptions - and creating new models - enabling the development of new classes of mental worlds.