基于分治思想的尺寸自动标注方法的研究与实现

摘要

提出了一种新的尺寸自动标注策略，即直接从三维模型出发完成二维标注，并引入分治思想将尺寸自动标注划分为基于特征模型、基于几何模型、基于二维图形等三个阶段.从特征模型出发，基于分治思想提出尺寸自动标注的二维与三维空间分治策略.在三维空间分治中，主要解决尺寸标注的完整性与合理性问题，提出形体分治、组合方式分治和工艺分治等三种分治策略；在三维到二维投影的二维空间分治中，主要解决尺寸标注的正确性与清晰性问题，提出投影分治、正确性分治和清晰性分治等三种分治策略.研制并实现了一个尺寸自动标注原型系统.研究成果可以与现有特征模型连接起来，具有一定的实用意义.同时，可以接受特征识别和三维重建的数据，从而使尺寸标注迈向新的阶段.%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.