> I don’t buy this either, speaking from experience using multiple commercial renderers.
It of course depends on exactly what is being rendered, but typically texture maps of assets for high quality cg are done at roughly the expected resolution of the final renders (rounded to a square power of 2). Typical assets will have three or four maps applied to each group of geometry, with higher quality hero assets having more groups.
> RenderMan, for example, does adaptive tessellation of displacement mapped surfaces because they will run out of memory with a uniform displacement.
It is specifically screen space displacement and this has been effective, but was originally crucial in the days where 8MB of memory cost the same as someone's yearly salary. In PRman actually polygons are even less of a burden on memory because of this with micropolygon and texture caches for efficiency, even with raytracing.
The real point here though is that nurbs don't really have much of an advantage, even in memory, because polygons are already lightweight and can be smoothed. Subdividing of polygons is typically not going to be too different from burbs and heavy polygonal meshes are likely to be extremely difficult to replicate with nurbs.
Don't get too caught up in exactly what is technically possible, this is about why nurbs are not an ideal form of geometry that anyone is trying to use again. Their disadvantages outweigh their advantages by a huge margin.