Oth law of model dynamics: In a finite (and usually very short) amount of time, users of a graphics system will generate a model that shall bring said system to its knees. The purpose of this paper is to discuss our experiences with the impact of megamodels on interactive virtual environments. We consider a megamodel to be any model that causes the Oth law of model dynamics to come into effect. We will demonstrate how working with megamodels quickly reveals the limitations of the graphics hardware and software being used to support the virtual environment. We will give examples, based upon our experiences on the Architectural Walkthrough Project here at the University of North Carolina at Chapel Hill (UNC), of the kinds of extra effort required to overcome these limitations.