Recent work has shown that implicit modeling using levels of details (LODs) is possible thanks to the use of subdivisioncurves as skeletons. However, the geometric skeleton of a 3D shape is, in the general case, a graph of interconnected curve segments and surface patches, the exclusive use of curve skeletons is therefore not sufficient. We present a model that uses a graph of interconnected subdivision curves and surfaces as a skeleton, on which a varying radius can be specified in order to

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... trol surface thickness. The subdivision levels of the skeleton provide levels of detail for the field function that defines the implicit surface. Its visualization is achieved by generating a coarse mesh that surrounds the skeleton. At high valence skeleton vertices, triangulation topology issues are managed by locally overlapping the iso-surface triangulations. The mesh is then adaptively refined in order to sample the current LOD of the implicit surface within an error tolerance. The last contribution is a new solution to the unwanted blending problem. It avoids blending between parts of the surface that do not correspond to neighboring skeletal elements, and ensures C 1 continuity everywhere. All these methods are integrated into an interactive modeling system, where the user can create, view and edit complex shapes at different levels of detail.