Auxiliary lines in three view drawings for 3D shape reconstruction using CSG method

The constructive solid geometry (CSG) method is applied to reconstruction of 3-D shapes from three-view engineering drawings. It is found that auxiliary lines must be added to most of the original drawings in order to generate a proper set of primitives. For this purpose, a systematic method for hierarchical auxiliary line generation is proposed. It keeps track of information on the depth in recursive line generation and of primitive operators to insure proper primitive operations. The proposed method was successfully tested on several typical engineering drawings