  Feature-based parametric modeling is the de facto standard in CAD. Boundary
representation-based direct modeling is another CAD paradigm developed
recently. They have complementary advantages and limitations, thereby offering
huge potential for improvement towards an integrated CAD modeling scheme. Most
existing integration methods are developed by industry and typically treat
direct edits as pseudo-features, where little can be said about seamless
integration. This paper presents an alternative method for seamless
parametric/direct integration, which allows parametric and direct edits to work
in a unified way. The fundamental issues and challenges of parametric/direct
integration are first explained. A framework is then proposed to handle those
information inconsistencies, based on a detection-then-resolution strategy.
Algorithms that can systematically detect and resolve all possible types of
information inconsistencies are also given to implement the framework. With
them, model validity can be maintained during the whole model editing process,
and then the discrepancy between direct edits and parametric edits can be
resolved. The effectiveness of the proposed approach has been shown with a
series of case studies and comparisons, based on a preliminary prototype.

Graphics;Computational Geometry