Selective knot insertion for symmetric, non-uniform refine and smooth B-spline subdivision
NURBS surfaces can be non-uniform and defined for any degree, but existing Subdivision surfaces are either uniform or of fixed degree. The resulting incompatibility forms a barrier to the adoption of subdivision for CAD applications. Motivated by the search for NURBS-compatible subdivision schemes, we present a non-uniform subdivision algorithm for B-splines in the spirit of the uniform Lane-Riesenfeld 'refine and smooth' algorithm. In contrast to previous approaches. our algorithm is independent of index direction (symmetric), and also allows a selection of knot intervals to remain unaltered by the subdivision process. B-splines containing multiple knots, an important non-uniform design tool, can therefore be Subdivided without increasing knot multiplicity. (C) 2008 Elsevier B.V. All rights reserved.
knot insertion non-uniform smoothing subdivision nurbs lane-riesenfeld