Autoregressive B-Rep Shape Generation with Parametric Surfaces

2026-07-19

AI Summary

Existing B-Rep generation methods rely on non-native representations such as point clouds or meshes, which discard the semantic information of parametric surfaces and thereby limit geometric accuracy and downstream usability. This work proposes ParaCAD, an autoregressive framework that, for the first time, enables native parametric B-Rep generation conditioned on input point clouds. By employing a surface-oriented tokenization strategy, ParaCAD explicitly encodes surface types and continuous parameters, generates parametric surfaces within constrained UV domains, and constructs valid B-Reps through global intersection computation. The method fully preserves CAD geometric semantics and substantially improves geometric accuracy, robustness, watertightness, and fidelity to the input point cloud, outperforming all existing point-cloud-based baselines across the board.

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.

Problem

• B-Rep generation
• parametric surfaces
• geometric fidelity
• CAD modeling
• point-cloud conditioning

Innovation

• parametric surfaces
• B-Rep generation
• autoregressive modeling
• surface-centric tokenization
• point-cloud-conditioned synthesis