Push-pull direct CAD modeling with movable neighboring faces for preserving G^1 connections
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B-rep model editing plays an essential role in CAD and motivates the very recent direct modeling CAD paradigm, which features intuitive push-pull manipulation of the model geometry. Boundary faces in a B-rep model could be connected in a smooth manner, typically G1 continuous, for functional, manufacturing or aesthetic reasons. Quite often, it is desirable to preserve such smooth connections during push-pull moves. This is, however, no trivial matter and introduces additional challenges. To preserve the G1 connections, neighboring faces of push-pulled faces need to be made movable, but their motions are not known explicitly. Consequently, it becomes challenging to track the geometry-topology inconsistency caused by these movable faces and to attain a robust update for push-pulled solid models. No effective ways exist in the literature to deal with the challenges; the industrial state of the art has implemented this function, but the challenges are not addressed satisfactorily and robustness issues are observed. This paper proposes a novel reverse tracking method to solve the above challenges, and then, based on it, presents a systematic method for push-pull direct modeling while preserving G1 connections. The developed method has been validated with a series of case studies.
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