Autoregressive B-Rep Shape Generation with Parametric Surfaces
Computer Vision and Pattern Recognition
Summary
The authors created ParaCAD, a method that improves how 3D shapes are made in CAD programs by focusing on the original types of surfaces rather than simplified points or grids. Their approach uses a special way to describe each surface exactly, keeping important details that other methods lose. ParaCAD starts by generating these detailed surfaces, then finds where they meet to form a complete 3D model. Tests show that their method makes more precise and reliable models that match the original input better than earlier point-based methods.
Authors
Dafei Qin, Rui Xu, Zeyu Shen, Kaichun Qiao, Hongyang Lin, Qixuan Zhang, Huaijin Pi, Lan Xu, Jingyi Yu, Wenping Wang, Taku Komura
Abstract
Generative CAD modeling has broad design and application potential. Despite significant advances in Boundary Representation (B-Rep) generation, the dominant representation in CAD, existing methods largely depend on uniformly sampled point- or grid-based geometry representations, sacrificing native surface types and parameters and thereby limiting geometric fidelity and downstream usability. We present ParaCAD, an autoregressive framework for point-cloud-conditioned B-Rep generation that directly operates on native parametric surfaces. ParaCAD introduces a surface-centric tokenization that explicitly encodes each face by its exact surface type and continuous parameters, preserving the intrinsic semantics of CAD geometry. Our model first generates parametric surfaces with constrained UV domains, and then constructs a valid B-Rep by globally intersecting these surfaces to recover edges and vertices. ParaCAD places point-cloud-conditioned generation at the core of B-Rep synthesis, making it practical for user-guided reconstruction and seamless integration into existing 3D generation pipelines. Extensive experiments demonstrate that ParaCAD produces accurate B-Reps with faithful point-cloud alignment, outperforming point-based baselines in geometric precision, robustness, watertightness and downstream usability.