CAD tools can use special adaptive algorithms to triangulate NURBS curves into meshes for rendering, so there is still a mesh there as far as I know. Beyond thi

CAD tools can use special adaptive algorithms to triangulate NURBS curves into meshes for rendering, so there is still a mesh there as far as I know. Beyond this, there is also the property of how the material responds to light. You can have multiple triangles appear smooth because they respond to lighting in a way that does not produce seams. "Smooth" rendering will use interpolated surface normals, and "flat" rendering uses per-face normals.