# A robust direct modeling method for quadric B-rep models based on geometry-topology inconsistency tracking

## TL;DR

This paper introduces a robust direct modeling method for quadric B-rep models that effectively detects and preserves smooth face-face connections during push-pull operations, enhancing model consistency and robustness.

## Contribution

It proposes a novel reverse detection approach to identify geometry-topology inconsistencies and a robust push-pull method for quadric B-rep models with smooth connections.

## Key findings

- Effective detection of inconsistency instants during push-pull operations
- Successful preservation of smooth face-face connections in quadric models
- Demonstrated robustness through case studies and comparisons

## Abstract

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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Source: https://tomesphere.com/paper/1906.08455