Abstract: Offset plays an important role in the field of CAD/CAM. The offset approximation
computation is more difficult for subdivision surfaces than parametric surfaces because
subdivision surfaces have no analytical expression. The proposed approach is an improvement of
two existed subdivision surface offset algorithms. Using the weighted progressive interpolation
(WPI) method avoids the mesh deviation caused by the traditional methods. The boundary offset
treatment is presented to obtain the uniform offset mesh. The proposed method avoids solving a
linear equation system and has the advantages of both local and global methods. The method can
be used to deal with either closed or open meshes. Offset approximation is an important operator
to the applications of Loop subdivision surfaces in NC machining. Some typical examples are
illustrated to demonstrate the efficiency of the proposed approach in the end.

Key words: offset, Loop subdivision surface, progressive interpolation, approximation