Color processing in reality-based 3D modeling of archeological artifacts using different survey techniques

Over the last few years, in the field archaeology, significant progress have been achieved in the use of techniques of digital media as tools for documentation, management and communication of cultural contents. Beside the progress in the field of digital visualization techniques we had a huge progress in the field of techniques for the acquisition and modeling of any kind of artifacts, such as architectural or archaeological ones. This progress has dramatically transformed the way in which the information are collected, processed and disseminated. The techniques used have evolved from state of the art and proven ones in digital surveying (active or passive sensor) to low-cost technologies based on structure-from-motion (SFM) techniques, a recent key technology able to combine friendly use with accurate results. Beside the mature and long-established digital survey the pipeline based on SFM techniques is similarly able to: - ensure high accuracy shape modeling; - maintain the consistency of color from the color detection, to texturing collimation on the mesh model till to digital visualization; - guarantee construction costs considerably lower. A three-dimensional digital model of an existing architectural artifact is qualified besides the model geometric accuracy compared to the real object, as well as by the fidelity of color, texture and reflectance properties of their surfaces. The detection of the color of the ancient artifacts of historical and monumental heritage, as it is linked to a number of factors including the subjective aspects of visual perception and objective characteristics of the light source as well as the way the object is being observed, isn’t an easy task. The problem is much more sensitive to the creation of 3D digital models from real objects. The paper describes a color processing system, low cost and to be user from non-expert operators (i.e. archaeologist and architects) that allow to enhance different techniques for reality-based 3D models construction and visualization of archaeological artifacts. This processing is developed in order to render reflectance properties with perceptual fidelity on a consumer display and presents two main improvements over existing techniques: a. it overcome our previous solution described in our paper in the 2011 edition of this same conference because is based on a more accurate color management system from acquisition to visualization and more accurate reflectance modeling; b. the color pipeline could be used inside well established 3D acquisition pipeline from laser scanner and/or photogrammetry. Besides it could be completely integrated in a SFM pipeline allowing simultaneous processing of color/shape data. In particular this last improvement is a significant feature allowing to solve two of main lack of the SFM pipeline: time compression and limited color fidelity of the final 3D model. We demonstrated our techniques using as case study an artifact of the Pompeii archaeological area, using data from a work on standardization of 3D reality-based model construction with the aim to be use them inside the 3D GIS of the local Soprintendenza.