Recent Researches in Computers and Computing Evaluation and visualization of 3D models using COLLADA parser and WebGL technology MIROSLAV MILIVOJEVIĆ, IGOR ANTOLOVIĆ, DEJAN RANČIĆ Computer Graphics and Geographic Information System Laboratory Faculty of Electronic Engineering, University of Niš Aleksandra Medvedeva 14, 18000 Niš SERBIA [email protected], http://www.elfak.ni.ac.rs Abstract - This paper describes the evaluation of the developed importer, as a subset of a larger GinisVisAjaxLibrary. The basic functionality of the importer is to read files in the COLLADA format, which is one of the most popular format today for the representation of 3D models. A lot of advantages derive from the architecture of this format, and the most popular are: handling of complex data over the Internet, the completeness of information needed for the visualization of complex 3D scenes, structural arrangement of data as well as, extensibility of the format by using extra tags. The importer was evaluated by determining the performance results presented in the form of tables and charts that include: downloading time, parsing time, number of textures, number of nodes, number of polygons, FPS and, FPS in an empty scene. The tests were executed in well-known browsers and on different operating systems. Key-Words: evaluation, WebGL library, COLLADA format, 3D models, importer, visualization 1 Introduction Although these two standards are very similar During the previous couple of years, 3D data regarding 3D data structure representation representation, as a substitute for desktop technology, they differ in their aims and purposes. environments for 3D visualisation [1,2], presents an This paper describes an evaluation of an importer important factor on the Web. In many domains of that we developed, which parses and converts 3D modern 3D implementing applications, methods for contents written in the COLLADA format into an presenting and managing sets and subsets of data universal mesh structure. Parser and mesh are have become more frequent, and this is exemplified structures which are a part of a larger Ajax based 3D by Web application which adequately represent: data visualisation library called complexes of buildings, museum interiors, flats, GinisVisAjaxLibrary [7]. GinisVisAjax Library uses kitchens, chemical compounds, human body (Body WebGL [8] technology in order to visualise 3D data Browser [3]), as well as a large amount of in Web browsers. The paper then describes the georeferenced data (GIS applications [4]). structure of the COLLADA format, its standardized The implementation of this kind of Web purpose, as well as environments and applications applications requires standard or specialized which use it. The specially designed architecture of modular Web services [5], databases, engines, the parser enables universality and uniformity of environments, libraries and formats in order to different objects encompassed in the mentioned represent complex elements on the scene. COLLADA format. Results are presented in tables Standardized formats which include all the required and graphs, and were obtained in the process of elements for representing 3D data on the scene, testing in the most frequently used Web browsers inserting animations and physics into the scene, as and operating systems. well as model description models, usually have a high level of data transferability, compatibility and usefulness. There are a large number of formats of 2 COLLADA file structure this kind, but the most used ones include: VRML, COLLADA is an abbreviated name of X3D, COLLADA[6], OBJ. COLLADA is a free COLLAborative Design Activity. This format open standard which uses an XML scheme to defines an XML scheme which enables 3D data present 3D content. This format has been developed presentation, simple editing of digital data and along with X3D standard in the last couple of years. compatibility with many 3D tools. This format ISBN: 978-1-61804-000-8 153 Recent Researches in Computers and Computing facilitates the interaction of applications over data in that support the use of this format and they are as 3D space. COLLADA is designed by an follows: Maya (ColladaMaya), 3ds Max unprofitable technological consortium Khronos (ColladaMax), Poser (v.7.0), LightWave 3D (v.9.5), Group [8]. Cinema 4D (MAXON). The most popular open- During the first phase of COLLADA scheme source applications and libraries that support this design, it was necessary to establish following format are: Google SketchUp, Blender and GLGE. assumptions: This is not a format that will be used COLLADA is focused on creating a series of by a game-engine. This format should be used for commercial and freeware tools. These tools allow tools design and 3D content that are supposed to the transmission and display of 3D content, provide the usage of modern interactive application especially in applications implemented from fields concepts. Many applications use COLLADA of science such as medicine, astronomy, chemistry format, but not as a final mechanism for 3D data and so on. This paper describes the evaluation of the delivery. Final users develop and test relatively COLLADA format. COLLADA format is one of the simple 3D content rather quickly. Model testing intermediate format (medium format type). The includes the usage of advanced rendering primary goal of this format is the presentation of techniques, such as vertex and pixel programs complex 3D models in a way that enables (shaders[9]). These assumptions led to setting the communication between tools and applications as goals which COLLADA format has managed to well as adapting to different platforms. Extra tags achieve; some of the goals[6] are: allow the definition of user information such as 1. To convert independent digital assets from descriptions of the models. COLLADA documents proprietary binary formats into a well-specified, that describe digital assets are XML files, usually XML-based, open-source format. identified with a .dae filename extension that means 2. To provide a standard common format so that a digital asset exchange. The same method can be COLLADA assets can be used directly in used for transfer or processing of 3D content tools existing content tool-chains, and to facilitate this of a scientific software solutions. Advantages and integration. usage of this format is great, as follows: suitable for 3. To provide an easy integration mechanism that delivery of interactive 3D Web content and business enables all the data to be available through applications that require the transfer of 3D data in COLLADA. real time, COLLADA format is very compatible 4. To be a basis for common data exchange among with Google Earth and supported in many Web 3D applications. applications. This feature applies at the following 5. To be a catalyst for digital-asset schema design domain of applications: online advertising, computer among developers and digital content creation games, virtual worlds (virtual reality), social (DCC), hardware, and middleware vendors. networks, GIS (Geographic information system) 6. To be adopted by as many digital-content users applications, medical visualization etc. as possible. The following text explains the important A large number of advantages of this format is elements of the COLLADA format. These elements derived from the XML technology. XML provides a are represented by XML tags or referenced to well-defined framework. Character sets such as: another element which are an integral part of them ASCII, Unicode, Shift-JIS are already covered by and some of them are: library visual scenes, library the XML standard, so when end users make some materials, library effects, library geometries and schema of data using the XML technology it library images. impacts on increasing interoperability. The example of XML schema allows for the technology to be <library_visual_scenes> fairly easy understandable without using its <visual_scene id="vis_scene"/> </library_visual_scenes> documentation. Another advantage is the existence <scene> of XML parser in almost every programming <instance_visual_scene url="#vis_scene"/> language for any platform. It makes files easily </scene> accessible for any application. Using this, developers can create very powerful tools and this is Here is an example of two elements such as made possible by the combination of multiple library_visual_scenes and scene element. The scene software packages and using of known technology element consists of an instance_visual_scene today. COLLADA format allows transport of data element which references to a property visual scene from one application for digital content creation to element. There are cases where there are more another. There are a lot of commercial applications scenes and their definitions are covered in ISBN: 978-1-61804-000-8 154 Recent Researches in Computers and Computing library_visual_scenes element. The scene may A material can have both image and colors. There contain various elements that describe the different are a lot of materials and images that must be loaded ambients of models, models and the different angles for one model and it could affect performance. of viewpoint. Library_images is an element that consists of a path or relatively path to the images. Image has a <library_geometries> image name and, a path that is embedded into <geometry name="cube" id="cube123"> int_form element. Image name must be matched <mesh> <source id="box-Pos"/> with a text that is embedded into newparam which <vertices id="box-Vtx">