Topological simplification of isosurfaces in volumetric data using octrees

Volumetric data, such as output from CT scans or laser range scan processing methods, often have isosurfaces that contain topological noise—small handles and holes that are not present in the original model. Because this noise can significantly degrade the performance of other geometric processing algorithms, we present a volumetric method that removes the topological noise and patches holes in undefined regions for a given isovalue. We start with a surface completely inside the isosurface of interest and a surface completely outside the isosurface. These surfaces are expanded and contracted, respectively, on a voxel-by-voxel basis. Changes in topology of the surfaces are prevented at every step using a local topology test. The result is a pair of surfaces that accurately reflect the geometry of the model but have simple topology. We represent the volume in an octree format for improved performance in space and time.