Combining 4- and 3-direction subdivision

  • Authors:
  • Jörg Peters;Le-Jeng Shiue

  • Affiliations:
  • University of Florida, Gainesville, FL;University of Florida, Gainesville, FL

  • Venue:
  • ACM Transactions on Graphics (TOG)
  • Year:
  • 2004

Quantified Score

Hi-index 0.00

Visualization

Abstract

4-3 direction subdivision combines quad and triangle meshes. On quad submeshes it applies a 4-direction alternative to Catmull-Clark subdivision and on triangle submeshes a modification of Loop's scheme. Remarkably, 4-3 surfaces can be proven to be C1 and have bounded curvature everywhere. In regular mesh regions, they are C2 and correspond to two closely-related box-splines of degree four. The box-spline in quad regions has a smaller stencil than Catmull-Clark and defines the unique scheme with a 3 × 3 stencil that can model constant features without ripples both aligned with the quad grid and diagonal to it. From a theoretical point of view, 4-3 subdivision near extraordinary points is remarkable in that the eigenstructure of the local subdivision matrix is easy to determine and a complete analysis is possible. Without tweaking the rules artificially to force a specific spectrum, the leading eigenvalues ordered by modulus of all local subdivision matrices are 1, 1/2, 1/2, 1/4 where the multiplicity of the eigenvalue 1/4 depends on the valence of the extraordinary point and the number of quads surrounding it. This implies equal refinement of the mesh, regardless of the number of neighbors of a mesh node.