SECAD-Net: Self-Supervised CAD Reconstruction by Learning Sketch-Extrude Operations
Pu LiJianwei GuoXiaopeng ZhangDong-Ming Yan
Proposes a self-supervised neural network that reconstructs editable CAD models from raw 3D geometry by learning implicit 2D sketch representations and differentiable 3D extrusion parameters without requiring ground-truth supervision.
Reverse engineering computer-aided design (CAD) models from scanned physical objects or raw 3D data is essential for manufacturing, maintenance, and design iteration when original technical files are unavailable. Conventional manual workflows are labor-intensive and require specialized operators, while existing automated methods either demand expensive labeled training data or generate models made of rigid mathematical primitives that engineers cannot easily edit.
The article demonstrates SECAD-Net, a self-supervised deep learning framework that reconstructs high-quality, fully editable 3D CAD models from unannotated shapes without requiring human segmentation or sketch labels. SECAD-Net evaluates the feasibility of learning sketch-and-extrude operations—the standard procedural workflow used in professional CAD software—directly from raw geometry in an end-to-end automated process.
To achieve this, the authors designed a neural network that decomposes an input 3D voxel grid into oriented extrusion boxes, predicts 2D profile sketches as continuous neural implicit fields, applies differentiable extrusion operations to form 3D solid cylinders, and combines them via standard union operations. The models were trained and benchmarked against leading supervised and unsupervised alternatives using thousands of engineering models from the ABC and Fusion 360 datasets, evaluating reconstruction accuracy, edge fidelity, and model compactness.
The evaluation yielded several key findings in order of importance. First, SECAD-Net achieved state-of-the-art geometric accuracy and surface fidelity across standard benchmarks, reducing symmetric Chamfer Distance on the ABC dataset to 0.330 compared to 0.471 for ExtrudeNet and 1.849 for UCSG-Net. Second, the method achieved these results with significantly fewer geometric primitives—averaging roughly 4 to 5 primitives per model, compared to 12 to 17 in competing constructive solid geometry frameworks—which produces simpler, cleaner CAD geometry. Third, the system demonstrated robust editing flexibility; the learned continuous sketch space enabled smooth interpolation between distinct CAD designs, and the resulting models exported directly into standard commercial CAD tools for downstream parameter adjustment.
These findings indicate that industrial reverse engineering can achieve higher modeling fidelity while substantially lowering data annotation costs. Producing compact, editable procedural features rather than static meshes directly reduces post-processing labor, shortens engineering lead times, and allows engineering teams to modify reconstructed parts immediately within existing CAD environments.
Organizations evaluating this approach should consider pilot testing the framework on standard prismatic component catalogs, while pairing it with existing CAD toolchains for interactive editing. Because the current implementation is bounded by sketch-and-extrude operations, deployment should focus on prismatic parts while further research extends the framework to support additional modeling operations such as revolves, sweeps, and fillets, alongside improved generalizability across highly irregular structures.
- Paper: Learning Implicit Fields for Generative Shape Modeling, Zhiqin Chen et al. (2018). Introduces implicit field representations for continuous geometric shape modeling and latent interpolation, providing the technical basis for SECAD-Net's implicit 2D sketch representation.
- Paper: DeepSDF: Learning Continuous Signed Distance Functions for Shape Representation, Jeong Joon Park et al. (2019). Establishes coordinate-based neural signed distance functions with latent code conditioning, a key continuous implicit formulation adapted by SECAD-Net for sketch space learning.
- Paper: Occupancy Networks: Learning 3D Reconstruction in Function Space, Lars Mescheder et al. (2018). Formulates continuous implicit surface learning for 3D reconstruction in function space, providing essential background for neural implicit shape decoding.
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