Volumetric models from 3D point clouds: The case study of sarcophagi cargo from a 2nd/3rd century AD Roman shipwreck near Sutivan on island Brač, Croatia

Multi-image photogrammetry can in favorable conditions even under water generate large clouds of 3D points which can be used for visualization of sunken heritage. For analysis of under-water archeological sites and comparison of artifacts, more compact shape models must be reconstructed from 3D points, where each object or a part of it is modeled individually. Volumetric models and superquadric models in particular are good candidates for such modeling since automated methods for their reconstruction and segmentation from 3D points exist. For the study case we use an underwater wreck site of a Roman ship from 2nd/3rd century AD located near Sutivan on island Brač in Croatia. We demonstrate how superquadric models of sarcophagi and other stone blocks can be reconstructed from an unsegmented cloud of 3D points obtained by multi-image photogrammetry. We compare the dimensions of stone objects measured directly on the corresponding 3D point cloud with dimensions of the reconstructed superquadric models and discuss other advantages of these volumetric models. The average difference between point-to-point measurements of stone blocks and the dimensions of the corresponding superquadric model is on the order of few centimeters.