Nurbs versus Meshes
Subdivision of Surfaces
NURBS versus multi-resolution Meshes
Multi-resolution meshes (MRM) like NURBS have the genereal capability of
performance adaptability.
From our point of view NURBS are having the following benefits over
MRM:
- Compact definition of NURBS, a MRM need to download all the
discrete data for all levels.
- Infinite Smoothnees, MRM can only refine and display up to the defined/downloaded
mesh data
- Animation of a few controlpoints are animating a significant part
of the surface, we assume that MRM are difficult or costly to animate
- Computer generated Model may have already be designed using NURBS,
so NURBS would be the natural data format
MRM could have the following benefits:
- storage of existing triangular mesh data or storage for 3D scanned
objects
- does not require NURBS quadrilateral patch structure
Subdivision Surfaces
Another technique, related to Bezier surfaces are subdivision surfaces.
Subdivion surfaces like Catmull-Clark are using a general Polygonal Mesh
similar to the VRML IndexedFaceSet as controlling mesh, instead of using
a grid of control vertices. The surface can approximate or interpolate
this control mesh.
The additional benefits to NURBS are that arbitrary topology meshes
are serving as control geometry. Subdivision Surfaces could be an ideal
replacement for Trimmed NURBSurface support.
The controlling mesh can be locally refined, a NURBS surface requires
a new row or colum of control vertices for refinement.