SDLib™ - The subdivision surface source code library¹

The subdivision surface source code library provided by SMS gives the ability to easily model complex shapes with hierarchical Catmull-Clark surfaces. Click to see graphic examples.

• SDLib offers:
• Portable C++ libraries
• Affordability and royalty-free use
• Full source code
• Quick response – most bugs are fixed in just a few days
• SDLib input:
• A polygon representation
• SDLib output may be either:
• A NURBS representation of the subdivision surface fully compatible with SMLib
• Polygonal tessellation of the subdivision surface
• SDLib’s high-level class design:
• Fully object-oriented approach: dozens of classes targeted to Surface, Face, Edge, Vertex, Iterators, Tessellators, etc.
• Evaluation gives positions, normals, or derivatives at any point on the surface
• SDLib editing gives power over:
• Control points at any level of the hierarchy
• Crease information at any level, for selected discontinuity of edges or points
• SDLib subdivision surface features:
• Can convert an arbitrary topology polygonal mesh to a smooth surface.
• Surfaces are built to be everywhere smooth, and C2 most places.
• Surfaces may be edited using control points, just as with NURBS.
• Surfaces may be edited at different levels of detail: fine, coarse, medium.
• Surface is exactly equivalent to bicubic NURBS patches nearly everywhere.
• Surface easily converts to polygons or NURBS.
• Surface can be evaluated everywhere.

Key Benefits

Subdivision surface functionality available in SDLib includes:

• Subdivision surface creation from a polygonal mesh:
• An input polygonal representation is read to give the basic topological layout of the subdivision surface.
• Any manifold mesh may be used, giving a wide range of shape possibilities.
• Resulting subdivision surface contains faces, edges, vertices at every level.
• Face, edge, and vertex operations. All faces, edges, and vertices in the subdivision surface are features at every level of the surface. These features all support:
• Adjacency queries: adjacent face, vertex, edge at the same level.
• Hierarchy: parent faces, finer-level feature access.
• Boundary queries.
• Ordering among features supports STL or other higher-level data structures.
• Additional vertex operations:
• Access CV position at this vertex.
• Set edit information at this vertex.
• Compute influence of all coarser-level vertices on this vertex, for convenience in recomputing position after edits.
• Compute position where this vertex maps on the surface.
• Compute normal at this vertex on the surface.
• Additional edge operations:
• Adjacency: adjacent face, vertex, edge.
• Hierarchy: sub edge access.
• Boundary queries.
• Crease management for the vertex: set and query crease information.
• Additional face operations:
• Compute position or normal at a (u,v) parameter within this face.
• Surface level operations. Each level of the subdivision surface can be set up as an object with:
• Provides iterators over all faces, edges, and vertices at this level.
• Counting of faces, edges and vertices at this level.
• Subdivide entire level to get a finer level.
• Compute coarser-level influence on all vertices at this level.
• Subdivision surface operations:
• Provides iterators over all base-level faces, edges, and vertices.
• Access to base-level faces, edges, and vertices.
• Access to vertices, faces, and edges at any level.
• Tessellation:
• Limit positions at any level may be output as a watertight polygonal mesh.
• Surface CVs at any level may be output as a connected polygonal mesh. This allows a means for topological modification at finer levels in the surface.
• Other tessellation varieties are planned.
• NURBS output:
• A closely approximating NURBS representation of the subdivision surface may be produced.
• The NURBS representation is compatible with SMLib.

Copyright © SMLib™, TSNLib™, GSNLib™, NLib™, SDLib™, VSLib™, and PolyMLib™ are trademarks of Solid Modeling Solutions.
ACIS is a registered trademark of Spatial Corporation.
All rights reserved.

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¹ SDLib Data Sheet     (PDF)