Annotation of Animated 3D Objects

AbstractThis paper presents a novel approach to illustrate dynamic procedures in tutoring mate-rials by analyzing corresponding animations. We propose two strategies: (i) to enhanceanimations with secondary elements (e.g., textual annotations and arrows) and (ii) togenerate visual summaries, i.e. illustrations where secondary elements provide indi-cations of the direction and the extent of moving objects in animations. We proposemetrics aiming at an unambiguous and frame-coherent layout in animations. Moreover,we integrated real-time algorithms to layout secondary elements in animations into aninteractive 3D browser. In order to test the impact of various conflicting functional andaesthetic layout requirements, our system contains several algorithms and strategies,which are compared in a user study. Finally, this paper presents result of applying ourapproach to enhance scientific illustrations and technical documentation. 1 Introduction Learning material (e.g., text books or visual dictionaries) incorporate many illustrations inorder to convey visual attributes of objects (e.g., shape, appearance) and spatial relationsbetween components in complex configurations. These visual entities are primary elementsin the layout of illustrations [Tuf97]. Moreover, textual annotations (labels) and other sec-ondary elements [Tuf97] (i) establish co-referential relations between visual and textualelements or (ii) encode directions of moving components and user actions in assembling ormaintenance processes (cf. the arrows in Fig. 1). Textual annotations either directly overlaythe referred object (internal labels) or are placed on the exterior of the geometric model(external labels), whereas reference lines establish the link between the label’s text and thereferred object.These 2D illustrations present 3D objects from a fixed point of view. For complex spatialconfigurations or complex-shaped objects an interactive exploration of 3D models facili-tates comprehension and learning (see [PPS99]). Therefore, several researchers developedreal-time layout algorithms that smoothly integrate secondary elements into interactive3D visualizations. Some of these real-time layout algorithms already considercoherency as-pects, i.e. they target at minimizing the flow of layout elements between subsequent framesduring user interactions.