Automatic detailing of parametric sketches by graph transformation

In the scope of planning and realizing large infrastructural projects, it is reasonable to create product models as multi-scale models comprising multiple levels of detail (LoD). To avoid inconsistencies among the different LoDs, it is necessary to apply parametric modeling techniques which allow the automatic preservation of the model's consistency across the different LoDs in the case of modifications. Previous research in this area has revealed that the manual creation of consistency preserving parametric product models is a very complex, time consuming and error-prone task. Therefore, research concerning the automation of the detailing processes is necessary. This paper presents a detailing automation approach which is based on graph transformations. It discusses how twodimensional parametric geometric models (sketches) can be represented by graphs and how detailing steps can be realized through graph transformation. A general approach to represent sketches by the use of graphs and the limitations applying to such an approach is described. It is discussed how geometric elements and corresponding parametric constraints of a sketch can be depicted by the nodes and edges of a graph and their attributes. Furthermore, the properties of the graph that are required for a nonambiguous representation are analyzed. Based on those requirements a corresponding graph rewriting system is introduced. The functional capability of the presented theories were validated through a prototypic implementation executing the stepwise detailing of a sketch representing a shield tunnel section.