Topology-Preserving Polygon Augmentation for Segmentation in Structured Visual Domains

TL;DR

This paper introduces a lightweight augmentation method that preserves polygon topology during geometric transformations, improving segmentation annotation consistency in structured visual domains.

Contribution

It proposes a novel topology-preserving augmentation strategy that repairs adjacency relations in polygon annotations without significant overhead.

Findings

Achieves near-perfect Cyclic Adjacency Preservation (CAP) across transformations.

Improves annotation consistency in polygon-based segmentation.

Integrates easily into existing preprocessing workflows.

Abstract

Geometric data augmentation is widely used in segmentation workflows, but polygon annotations are often assumed to remain valid after transformation. This assumption can fail in structured domains such as architectural floorplan analysis, where a region may contain an interior void encoded as part of a single ordered polygon chain. Cropping or clipping can remove bridge vertices in this chain, causing one semantic region to split into disconnected components. We propose a lightweight topology-preserving augmentation strategy that repairs missing adjacency relations in index space while preserving the original vertex order. The method adds minimal overhead and can be integrated into existing preprocessing workflows. Experiments show that the proposed approach achieves near-perfect Cyclic Adjacency Preservation (CAP) across common geometric transformations and improves annotation consistency in polygon-based segmentation.