Abstract
This study proposes a non-manifold shell operation which uniformly manipulates solids and surfaces as shells, in order to enable designers to realize free generation of shapes. This report first describes definitions of shell and non-manifold shell operations and presents some examples of them. Next, it proposes direct cancel operations for the shell operations to modify generated shapes. The non-manifold shell operation uniformly processes a regularized set operation, an extraction of solids by automatically detecting closed shells from a complex shell which is combination of solids and/or surfaces. Its direct cancel operation is an operation which recovers a shape, independently from a sequence of operations, to one before the designated operation was executed. This cancel operation is applied to efficient parametric design by recovering the shape after changes of parameters.
