Modeling method for sorting dependencies among geometric entities

摘要

A system and method for geometric modeling particularly useful for conceptual design in a mechanical CAD system. Geometric modeling includes not only geometric information, but other engineering and design constraints as well. The present method solves this geometric constraint satisfaction problem using graph based solution techniques. Constraints are graph sources of dimensional, translational, and rotational degrees of freedom while the geometric entities in the model are graph sinks. The method generates an ordered dependency list of geometric entities by allocating degrees of freedom according to a geometric entity's ability to absorb them. The ordered dependency list is used as an execution sequence if a constraint is changed. If a constraint or geometric entity is added or deleted from the model, the ordered dependency list is recomputed. A modeler can thus conceptualize incremental changes in the model while satisfying the imposed constraints. Because the computational complexity is linearly related to the problem complexity, the graph based method is well suited to incrementally modeling complex geometric problems--particularly 3D geometry--in a robust fashion.