Screen space rendering statistics were gathered from 150 3D objects, each modeled by between 2K and 40K triangles. While there is wide variance by individual object, the overall trend is that the distribution of triangles by screen size is roughly exponential in the direction of small triangles. From a subjective esthetics point of view, tessellations required 10K visible triangles per quarter million pixels covered for acceptable results.
Michael F. Deering