 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 .
Boundary representation ( B-rep ) model editing plays an essential role in computer-aided design and motivates the very recent direct modeling paradigm, which features intuitive push-pull manipulation of the model geometry. In mechanical design, a substantial part of B-rep models being used are quadric models (composed of linear and quadric surfaces). However, push-pulling such models is not trivial due to the possible smooth face-face connections in the models. The major issue is that, during push-pull moves , it is often desirable to preserve these connections for functional, manufacturing, or aesthetic reasons, but this could cause complex inconsistencies between the geometry and topology in the model and lead to robustness issues in updating the model. The challenge lies in effectiveness towards detecting the instants when geometry-topology inconsistencies occur during push-pull moves. This paper proposes a novel reverse detection method to solve the challenge and then, based on it, presents a robust method for push-pull direct modeling while preserving smooth connections. Case studies and comparisons have been conducted to demonstrate the effectiveness of the method .
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Boundary representation (
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CAD
computer-aided design
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CAD
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Boundary faces in a
In mechanical design, a substantial part of
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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
models being used are quadric models (composed of linear and quadric surfaces). However, push-pulling such models is not trivial due to the possible smooth face-face connections in the models. The major issue is that,
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. This is, however, no trivial matter and introduces additional challenges. To preserve the G1 connections
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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
it is often desirable to preserve these connections for functional, manufacturing, or aesthetic reasons, but this could cause complex inconsistencies between the geometry and topology in the model and lead to robustness issues in updating the model. The challenge lies in effectiveness towards detecting the instants when
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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.
inconsistencies occur during push-pull moves.
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tracking
detection
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above challenges,
challenge
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systematic
robust
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G1 connections. The developed method has been validated with a series of case studies
smooth connections. Case studies and comparisons have been conducted to demonstrate the effectiveness of the method