Declarative 3D Approaches for Distributed Web-based Scientific Visualization Services Yvonne Jung Johannes Behr Fraunhofer IGD Fraunhofer IGD Darmstadt, Germany Darmstadt, Germany [email protected] [email protected] Timm Drevensek Sebastian Wagner Fraunhofer IGD Fraunhofer IGD Darmstadt, Germany Darmstadt, Germany [email protected] [email protected] ABSTRACT Android, RIM, WindowsPhone), different desktop systems, Recent developments in the area of efficient web-service ar- cloud bases etc., which typically make cross-platform devel- chitectures and the requirement to provide applications not opment complicated and time consuming. In this regard, just for a small expert group lead to new approaches in web technologies incl. web-service architectures are rather the field of web-based (scientific) visualization. The just common and can overcome these issues by interconnecting emerging support for GPU-supported and therefore high- all these diverse approaches. Moreover, web browsers are performance 2D and 3D graphics in modern web-client im- converting more and more towards full runtime environ- plementations and standards provide new application envi- ments for whole applications and with WebGL or Stage3D, ronments, which are especially interesting for the demands 3D-capable browsers are now broadly available, too. of scientific visualization solutions. Thus, in this paper we present a web application deployment architecture that aims However, this does not solve the often intricate processes at supporting decision making processes more efficiently. We to develop applications, where one can distinguish between also show that current approaches in the field of declarative two main types. For one thing, we have interactive processes 3D techniques are useful for client-side rendering as well as with creative and individual components such as games with for a large number of processing and visualization aspects. their manual or semi-automatic tool chains (e.g., DCC tools like 3ds Max and game editors like Unity3D) that focus on Categories and Subject Descriptors isolated applications. For another, there are automatable processes that typically are complex and distributed, which H.3.5 [Information Systems]: Online Information Ser- can be realized by means of a web-service architecture. In vices|Web-based services; I.3.6 [Methodology and Tech- the context of this paper, we focus onto the latter approach niques]: Standards|Languages; I.3.7 [Computer Graph- by presenting a fully automated Web Service Portal, which ics]: Three-Dimensional Graphics and Realism|Virtual Re- thereby allows generating e.g. 2D/3D mash-ups for design ality review, city planning or similar decision making tasks. Keywords Generally spoken, distributed data-centered applications are X3D, HTML5, WebGL, DOM, Web Integration, Transcoder, one of the common implementation concepts for scientific vi- Web Services, Service-oriented Architectures, X3DOM sualization solutions today to process huge data sets. There- fore, utilizing web-service architectures or even cloud-based 1. INTRODUCTION solutions are just the next logical step. Recent develop- With the advent of 3D Internet, there is a strong trend to- ments in the area of high-performance web-service archi- wards 3D data and documents (like 3D scanners and print- tectures and the requirement to provide applications not ers, geo-referenced data, and Augmented Reality) as well as just for a small expert group lead to new approaches in a convergence of application platforms (e.g. W3C WebApps, the field of web-based visualization. The emerging support HTML5, etc.) towards web-based contents. However, we for hardware-accelerated and therefore high-performance 2D still have various operating systems with very different soft- and 3D graphics in modern web clients and standards pro- and hardware requirements such as smart phones (e.g. iOS, vide a new application environment, which is especially in- teresting for the demands of scientific visualization solutions. Therefore, some visualization packages (like ParaView with ParaViewWeb from Kitware1) already use this opportunity to move the established application model to a web and cloud-based solution. Deploying current application models Copyright c 2012 for the individual papers by the papers' au- to a new environment is just the first step. However, this thors. Copying permitted only for private and academic purposes. field is not yet explored to utilize its full potential. This volume is published and copyrighted by its editors. 1 Dec3D2012 workshop at WWW2012, Lyon, France http://paraview.org/Wiki/ParaViewWeb challenging application domains: medical imaging and radar meteorology. Performance, scalability, accuracy, and secu- rity are some of the many challenges that must be solved Figure 1: Coarse sketch of the visualization pipeline. for 3D web applications, esp. since WebGL is still based on the old Shader Model 2.0 (like on the NVidia GeForce 5900 series introduced in 2003). Thus, the web-application deployment component presented in this paper helps supporting decision making processes Another alternative method for representing 3D graphics is more efficiently, and the benefits include the following four using point clouds, which is a set of points in 3D space with major aspects: attributes. This is especially of interest, since 3D scanning { leveraging new GPU-accelerated 2D and 3D client APIs; devices such as LiDAR equipment and sonar scanners de- { achieving interactivity while combining traditional client- liver their data as point clouds. One recent framework to and server-side rendering techniques; simplify the streaming and rendering of point clouds based { providing new user experiences while considering scalabil- on JavaScript and WebGL [15] is \XB PointStream" [20]. ity and security in open web-based environments; { automating and optimizing data preparation processes for In [22], the authors propose a WebGL-based framework for web-specific environments through web server infrastructures. representing reflectance information via Bidirectional Tex- ture Functions (BTF), which allows for the progressive trans- 2. RELATED WORK mission and interactive rendering of digitized artifacts con- For the design of the proposed web-service architecture sev- sisting of 3D geometry and reflectance information. This eral domains and technologies are relevant. Corresponding is achieved by employing a novel progressive streaming ap- work is thus briefly described within this section. proach for the huge BTF data set that allows the smooth interactive inspection of a steadily improving model during 2.1 Scientific Visualization download. Analogously, the X3DOM framework [3, 4] cur- To provide important features for scientific visualization (cf. rently follows a similar approach for lightweight geometry e.g. [6] and [14]) in a specialized web application, the appli- compression and transmission via so-called image geometries cation must be able to handle visualization-specific represen- that likewise utilizes image compression techniques. tations that consist of registered and merged point, surface, and even volume data as well as the corresponding meta in- 2.3 Declarative (X)3D in HTML5 formation. But having the raw data to be visualized readily The open ISO standard X3D [8] provides interactive 3D available is only the very first step, as is shown in Figure 1 graphics for the web and is the only standardized 3D de- with a rather simplified visualization pipeline. Usually, after ployment format. It differs from other 3D formats like the data acquisition the information is re-sampled onto a struc- interchange format Collada [1] in that it also includes the tured regular grid before filtering the data accordingly (a scene's runtime behavior. The X3D standard already pro- discussion of common data representations including multi- vides point and surface primitives. Typically, the visual el- resolution and adaptive resolution representations for large ements are described by their boundary representation, e.g. data sets can be found in [14]). Then, the scalar, vector, or via an \IndexedTriangleSet" node. Volume rendering will be tensor values of the data set are mapped to visual represen- part of the next spec revision. Therefore, the Web3D med- tations that can be rendered [6]. Well-known examples here ical working group has presented a sample implementation are volume rendering or flow visualizations in CFD [17]. [11] and an ISO/ IEC PDAM extension for a volume render- ing component in X3D, which also has answers to DICOM For multi-dimensional, multi-variate/ multi-modal, and prob- requirements for n-D presentation states [19]. ably even time-varying data, visualization is much more in- tricate, since first the registration between different data In addition, since most geo-referenced data is provided in sets including the thereby introduced uncertainties has to be a geodetic or projective spatial reference frame, the X3D handled as well as data fusion aspects and the calculation Geospatial component includes conventions that are defined of derived quantities (e.g. the strength of correlation be- by the Spatial Reference Model and thereby provides sup- tween two different variables) to improve the visualization port for geographic and geospatial applications [8, 16]. With [6]. In this regard, not only the choice of an appropriate surface, volume, and geo-spatial components X3D already visualization technique but also the possibility to interac- provides a solid foundation for scientific visualization tasks