Research on Automatic Dimensioning Based on Divide and Conquer Strategy

In view of intrinsic contradiction between 3D space modeling and 2D dimensioning scheme, it is comparatively difficult to fulfill automatic dimensioning in 2D space. A new strategy to solve this contradiction is put forward, namely 2D dimensioning directly starts from 3D model. The divide and conquer strategy is applied to resolve automatic dimensioning in three phases, that is, dimensioning the feature model, dimensioning the geometric model and dimensioning the projected entities on 2D graphics directly. The first phase of feature model is studied in this paper and the divide and conquer strategy is applied to 3D space modeling and 2D dimensioning scheme. The 3D space modeling mainly focuses on the integrity and rationality of dimensioning. The elementary constituents of form features are abstracted, their combination modes are classified and manufacturability evaluation is carried out to refine the dimensioning scheme. The 2D dimensioning scheme focuses on the validity and legibility of dimensioning. It deals with the clearness of presenting 3D objects in 2D views, the validity of dimensioning scheme and legibility of dimensions. A prototype system of automatic dimensioning is under development. It is compatible with the existing CAD feature models and can accept the results of feature recognition and 3D reconstruction.