Solid Offset and Shelling

實體偏移是從幾何偏移演進而來，其目的是將實體的外形向外延伸或向內收縮固定的厚度而成為一個新的實體。薄殼化屬於實體偏移的延伸應用，實體模型依其外形及指定的厚度轉變成為薄殼狀的實體模型。在建立偏移實體時，常因為偏移的距離太大，使得實體的邊界過度扭曲甚至自交，造成無法形成封閉的實體。本研究提出實體偏移之法則，並延伸此法則至實體薄殼化，利用偏移運算或薄殼化運算將邊界表示法建構之實體模型轉換成另一實體模型，在偏移運算及薄殼化運算的過程中提供自交的檢驗及修正方法。

Solid offset is derived from the geometry offset and is a procedure where a uniform thickness is added or removed from a solid model. Shelling is an extended application of solid offset and is a procedure which turns a solid model into a thin-walled shell of constant thickness. Self-intersection often occurred in the process of solid offset operation or shelling operation. An algorithm of the solid offset operation and shelling operation based of on boundary representation (Brep) solid models are given. In this algothirms, self-intersection is detected and corrected to generate correct solid models.