SIDe-HBIM: Single-Image Depth Inference as a Tool for Semi-Automatic Decorative Modeling

This paper introduces SIDe-HBIM (Single-Image Depth inference for HBIM), a semi-automated image-to-BIM pipeline aimed at improving the integration of architectural decorative elements into HBIM environments. The research addresses the difficulty of representing geometrically complex yet information-oriented heritage components when traditional survey techniques are impractical or disproportionate. Starting from a single photographic input, the methodology combines AI-based depth estimation, quantitative computational evaluation and parametric modeling to generate lightweight, morphologically coherent 3D elements suitable for non-photorealistic HBIM applications. Multiple image-to-depth models are processed in parallel and ranked through a weighted synthetic index based on geometric and structural indicators, after which the selected depthmap is converted into a continuous NURBS surface and integrated into a BIM environment. Application to three heterogeneous case studies from the Basilica of Santa Maria degli Angeli (Assisi) demonstrates that SIDe-HBIM is particularly effective for bas-reliefs and moderate-relief decorative apparatuses, offering a reproducible and efficient alternative for HBIM-oriented documentation.