An approach for creating solid models from orthogonal views by identification of Boolean operations

An approach is presented for automatic reconstruction of solid models from 2D drawings consisting of lines, arcs and Bézier curves. An algorithm was developed for drawings consisting of two orthogonal views with dashed hidden-lines. In this paper, a 3D object is considered to be composed of one, or more than one, part. The idea of the algorithm is to extract closed loops from the 2D views and to match loops from two views in order to build separate parts. These parts are then combined by Boolean operations so as to finally form the 3D object. The necessary vertices, edges and faces of the object are determined by a suitable sequence of operations, such as union and difference. The parts consist of either rotational solids or the Boolean intersection of the extrusions of two orthogonal profiles. Loop extraction is based on some simple concepts in topology and differential geometry. Parts combination is based on the process of operation recognition. Whilst the method has some limitations, it is seen to be suitable for many engineering representations of a simpler kind.