TRACE-ing the Gaps: Mapping Interventions on Incomplete 3D Meshes

Abstract. The 3D digital representations of physical objects are inevitably marked by gaps and imperfections arising from both technological limitations and contextual acquisition constraints. These shortcomings often necessitate manual or semi-automatic interventions, introducing elements of subjectivity into the modelling process. Despite the increasing use of 3D technologies across the Galleries, Libraries, Archives, and Museums (GLAM) sector, a standardised methodology for classifying and documenting mesh incompleteness is still lacking, undermining the transparency, reusability, and interoperability of such data. This paper addresses two core research questions: (RQ1) Which acquisition conditions can be identified as the main contributing factors to the occurrence of holes in 3D meshes? (RQ2) How can topological modifications resulting from the manual integration of holes in 3D cultural heritage models be automatically tracked and visualised? To address these questions, we propose a classification framework grounded in five case studies drawn from two digitisation campaigns conducted within the CHANGES project (Spoke 4). We further present a workflow for a post-hoc, method-agnostic identification approach for the automatic tracing and interactive visualisation of topological edits, implemented within a Web3D environment based on the ATON framework. Situated within a pipeline that adheres to FAIR principles, this methodology aims to enhance the interpretability and scholarly value of digital reconstructions by embedding provenance-aware metadata. Building on established approaches in critical architectural reconstruction, this work proposes a methodological extension tailored to the nuanced management of holes in cultural heritage 3D models.