FINAL WORKSHOP OF GRID PROJECTS “PON RICERCA 2000-2006, AVVISO 1575” 1 Laser Scanner Technologies and 3D Models Integration: Analysis and Methodological Approach D. Abate 1 , M.C. Baracca 2 , R. Ciavarella 3 , G. Furini 4 , S. Migliori 5 , S. Pierattini 6 1 ENEA, Bologna, Italy, dante.abate@enea.it 2 ENEA, Roma, Italy, cristina.baracca@enea.it 3 ENEA, Portici(NA), Italy, roberto.ciavarella@enea.it 4 ENEA, Bologna, Italy, graziano.furini@enea.it 5 ENEA, Roma, Italy, migliori@enea.it 6 ENEA, Bologna, Italy, samuele.pierattini@enea.it I. INTRODUCTION T he attention of the scientific community Abstract— The 3D scanning laser systems towards 3D digitizing techniques applied available at ENEA, different for technical to cultural heritage is related to the specific characteristics, allow to fullfil a wide range of diagnostic and monitoring requirements in the needs of conservation: in terms of time and artistic and cultural heritage field. Since each reliability, digital archives of high quality three- scanning device is provided with proper file dimensional models would constitute a great formats and software package for the data improvement in respect of the past traditional management and the reconstruction of the 3D methods of documentation. Digital archives are objects acquired, the main problem in durable and unalterable, and thus can be used constructing complex graphical scenes is to integrate the 3D models preserving all the as reference for degradation monitoring and information detected. Accordingly, the restoration activities. The scanning laser development of Virtual Reality applications systems available at ENEA, acquiring 3D requires the analysis of the model file formats and objects and detecting information like position, the format conversion tools in order to define a color and reflectance of each point, allow to methodology allowing to integrate the different meet a wide range of diagnostic and monitoring systems and to build 3D scenes navigable by means of VR environments. As example, this requirements in the artistic and cultural heritage paper refers to the development of a virtual field. Each laser scanning system is provided museum exhibiting the different 3D models, with a specific software for the data acquired during various scanning campaigns, management and analysis, capable to produce navigable by means of VR environments, 3D models of the scanned objects in specific available through the ENEA Grid. output file formats. A test case was adopted, in Index Terms — ENEA, CRESCO Project, GRID order to define a methodology allowing to Computing, Virtual Reality, Cultural Heritage, include such 3D models in the same graphical Laser Scanner Technology, 3D Models. scene. The objective was to develop a “Virtual Museum” in which to set up exhibitions, inserting/removing 3D models produced by
FINAL WORKSHOP OF GRID PROJECTS “PON RICERCA 2000-2006, AVVISO 1575” 1 different laser scanner system and to navigate the 3D graphical scene by means of the Since each scanning device is provided with VegaPrime [1] environment or the proper output file formats and software OpenSceneGraph [2] toolkit available by packages for the data management and the means of the ENEA-Grid [3]. The integration reconstruction of the 3D objects acquired, the of the different laser scanning systems consists main goal in realizing complex graphical in the definition of the conversion procedures scenes is to integrate the 3D models in a VR of the 3D models, from the specific output file application, through format conversion formats to the OpenFlight format (.flt) [4], preserving all the detected information. supported by both the chosen virtual reality environments. B. 3D Models The availability of 3D digital models not only A. Laser Scanner Systems in ENEA does support the promotion and diffusion of the heritage by means of multimedia applications, Laser scanning technology allows the digital but also permits to improve many processes acquisition of three-dimensional objects as like cataloguing, study, preservation, point clouds. The digital geometric description restoration planning and simulation, fragile of the object is discrete, the resolution selected artefacts monitoring, virtual reconstruction, for the acquisition defines the density of the replica production. 3D laser scanner devices point cloud and so the details of the allow to analyze real-world objects or representation. Every point is described by a environments, to collect data (point clouds) on spatial position in x y z coordinates respect to its shape and possibly its appearance (i.e. the origin represented by the position of the color/reflectance). The collected data can then scanner. Due to different characteristics of the be used to construct digital, three dimensional laser scanner systems in ENEA, it is possible to models useful for a wide variety of choose, case by case, the more suitable to be applications, including the exposition in a applied and to produce 3D models of objects “virtual museum”. with size ranging from tens of centimeters to tens of meters. Here below, some 3D models produced by means of: ! ITR (Imaging Topological Radar) ! VIVID 900 developed by ArtVisLab-ENEA [5] Output file format: PLY (Polygon File Format) with VCG extension library; SW package: ISIS ply viewer; ! HDS3000 by Leica-Geosystem [6] Output file format: DXF, DWG, MDL and PTS; SW package: Cyclone and Cloudworks module for Autocad; ! VIVID 900 by MINOLTA [7] Output file format: STL, DXF, OBJ,ASCII and VRML; SW package: Advantage Polygon Editing Software; ! Desktop 3D Scanner by NextEngine [8] Output file format: STL, OBJ, VRML and Old soldier and young soldier 3DS; SW package: ScanStudio CORE TM . (Museum Certosa, Bologna)
FINAL WORKSHOP OF GRID PROJECTS “PON RICERCA 2000-2006, AVVISO 1575” 1 ! ITR ! HDS3000 Emperor Costantino marble head (Museum, Frascati) Basilica - Juvanum archaeological site C. Conversion to OpenFlight format The Open Flight format (.flt) is supported by Polichrome pot 1 both VegaPrime and OpenSceneGraph; from the analysis of the 3D models proprietary file formats and the format conversion tools, it was possible to define the 3D models conversion methods to OpenFlight format without loss of information. After analyzing and testing input and output formats of the most common Polichrome pot 2 software for 3D model conversion, the following conversion schemes were defined: for PLY format: ! Desktop 3D Scanner or Small artefact
FINAL WORKSHOP OF GRID PROJECTS “PON RICERCA 2000-2006, AVVISO 1575” 1 and for STL or OBJ materials, lights, etc., to insert in the graphical scene some of the 3D models produced by means of different laser scanner systems. Once converted in the OpenFlight format, each model was correctly scaled and placed in the navigable museum environment, as shown in the pictures below; the Juvanum archaeological site model can be accessed navigating through a picture of the Juvanum archaeological park [12] placed on an internal wall. D. Positioning and scaling models in a 3D scene Since every scanned object is represented in a 3D space, accordingly to the space configuration of the used scanner system, it is useful to refer all the models to the same space: by means of Accutrans 3D [9] it is possible to redefine the origin for each model and so refer it to the same space. Moreover, due to the different characteristics of the laser scanner systems, two further aspects must be taken in to account: ! Different scaling factor are applied to models originated by different systems; ! The number of points defining the mesh of a model usually is much higher than the one required for a VR application. Museum exterior LynX Prime, the editing tool of VegaPrime, allows to define the “scale” parameters to be applied along each axis to an .flt model. In this way it is possible to re-establish right proportions to the models. The number of points in a mesh can be decreased through the application of decimation algorithms. For example, MESHLAB [10] allows to choose among some filter and statistical decimation algorithms. E. Virtual Museum In the framework of the ENEA CRESCO Museum interior project [11], it was decided to develop an application, running on the ENEA Grid, simulating a museum exhibition; that is, starting from the 3D geometrical modeling of a museum architecture equipped with textures,
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