2026 Jiang Canonical CAD Boundary Representations

Boundary representation (B-rep) serves as the standard format utilized by contemporary CAD systems for parametric 3D models, with the same solid potentially represented by diverse B-reps due to various operations, geometry kernel rebuilding, and export settings. This study demonstrates that established B-rep encoders exhibit significant vulnerabilities to variations in B-rep representations of identical solids, skewed by standard benchmark perturbations, inherent variations from CAD software, and discrepancies in designer modeling approaches, as evidenced by a human dataset curated in FreeCAD. The performance of widely-adopted B-rep encoders was found to deteriorate drastically under these circumstances. In response, we introduce the canonical region graph, a novel input representation whose nodes, features, and coordinate frame are derived from the solid itself, and we present theoretical invariance guarantees concerning repartitioning and rigid motions. Our method achieves performance metrics that match the strongest baseline across standard benchmarks while demonstrating stability across all applied perturbations.