## 1 Introduction  
In the comprehensive industry chain of engineering software, reverse engineering computer-aided design (CAD) software plays a pivotal role [1]. Through the utilization of computers and three-dimensional (3D) scanning devices, this software assists engineers in swiftly realizing 3D reconstructions of physical objects in reverse and facilitates variant design [2]. It significantly improves the efficiency of product design in enterprises, shortens the research and development cycle, and is increasingly acknowledged as a crucial design tool for industrial enterprises.  
Currently, digital 3D models in reverse engineering CAD software are commonly represented as manifold meshes [3] derived from scanned 3D point clouds. A manifold triangular mesh is a surface model that discretizes the surface of a CAD model and produces triangular facets to approximate the surface [4]. Manifold triangular mesh data can express only the geometric and topological relationships among the vertices and edges of triangular facets, and they lack the ability to represent the high-level semantic and design aspects of CAD models. Furthermore, CAD model surfaces often include planar and quadratic surfaces, resulting in sparse and sharp-edged manifold meshes [5]. Reconstructing manifold meshes into continuous geometric objects such as B-splines or NURBS and applying them to CAD software can lead to shape distortion and the loss of semantic features.  
The development of geometric modeling technology has advanced through four distinct stages: wireframe modeling, surface modeling, solid modeling, and feature modeling [6]. Feature modeling acts as a direct representation of the design intentions within solid CAD models, enabling the expression of elevated semantics and design details [7]. This function significantly aids in the seamless integration of CAD/CAM and propels progress towards higher-dimensional digital twin modeling [8]. Hence, the reconstruction of solid CAD features from manifold triangular meshes acquired through reverse engineering CAD software is crucial.  
In this paper, we present a novel computational paradigm for reconstructing solid CAD features from the surface of a segmented manifold triangular mesh. We make the following contributions in this paper.  
* We present a unified mathematical representation for categorizing four common solid CAD features as generalized swept bodies driven by cross-sectional sketches and feature paths. It facilitates the efficient realization of feature reconstruction through the CAD kernel.
* Utilizing a numerical optimization-based approach, we perform geometric processing on the segmented manifold triangular mesh patch, leading to the extraction of cross-sectional sketch curves and feature paths from its surface.
* We demonstrate how this computational paradigm enables parametric and variant designs of the manifold triangular meshes acquired from 3D scanning, enhancing their compatibility with personalized 3D-printed models.  
The remaining sections of the paper are structured as follows: Section 2 presents a review of prior efforts in recovering or extracting solid CAD features from unstructured data like 3D point clouds or polygon meshes. Section 3 outlines our computational paradigm. In Section 4, we detail our method for extracting cross-sectional sketch curves and feature paths of four types of solid CAD features from segmented manifold triangular mesh patches. Section 5 presents the experimental results of our approach for reconstructing four types of solid CAD features. Concluding remarks end the paper.