Design Nomenclature / Digital Model Making
Subdivision Surface
Also called sub-d, subd, SDS, subdivision modeling
A smooth limit surface defined by a coarse control mesh — the cage — plus a refinement rule applied repeatedly. You edit the cage; the surface you see is derived from it and lies inside it. Sharpness comes from local density or explicit creases, not from a curve degree.
In practice
Said “sub-d”. Quad cages behave predictably because the rule was written for them; triangles and poles converge to pinches and shading dents.
Not to be confused with
- SmoothingTwo different things under one word. Mesh smoothing — relax — moves vertices toward the average of their neighbours, evening out spacing and losing volume as it goes. Smooth shading changes no geometry at all: it interpolates normals across faces so a faceted surface reads as curved. The silhouette gives it away.
- NURBS ModelingBuilding form as a patchwork of mathematically exact rational spline surfaces, each a grid of control points with a degree and a knot vector. Resolution is evaluated on demand, so the surface is exact at any zoom. The work is patch layout, and holding continuity where patches meet.