Retargeting Vector Animation for Small Displays Vidya Setlur Northwestern University and Nokia Research Center Xuejin Chen USTC and Microsoft Research Asia Yingqing Xu Microsoft Research Asia Bruce Gooch Northwestern University Figure 1: Preserving the spatial detail in important objects from a source animation to a smaller sized animation. Abstract We present a method that preserves the recognizability of key ob- ject interactions in a vector animation. The method allows an artist to author an animation once, and then output it to any display de- vice. We specifically target mobile devices with small screen sizes. In order to adapt an animation, the author specifies an importance value for objects in the animation. The algorithm then identifies and categorizes the vector graphics objects that comprise the anima- tion, leveraging the implicit relationship between extensible Mark- up Language (XML) and scalable vector graphics (SVG). Based on importance, the animation can then be automatically retargeted for any display using artistically motivated resizing and grouping algorithms that budget size and spatial detail for each object. CR Categories: I.3.3 [Computer Graphics]: Picture/Image Generation—Display Algorithms; Keywords: perception, animation, small displays, WWW applica- tions, information visualization, non-photorealistic rendering, vec- tor graphics, XML 1 Introduction Advances in mobile devices and wireless telecommunication pro- vide users with ubiquitous access to online information and ser- vices. However, user access and interaction are still quite restricted with regard to the display of imagery such as animations, diagrams, maps, and charts. There exists a growing need for the effective adaptation of imagery for small size displays. This work presents an algorithm for retargeting vector based animations while main- taining the recognizability of object interaction. Effective display consists of understanding the communication goal of some form of imagery and then fitting that imagery to the display device in a manner that aids this goal. In most animation, the story is communicated to the viewer via the interaction of a few key ob- jects. Remaining objects in the scene provide a context for this interaction, and are referred to as contextual objects. In order to achieve the communication goal of an animation on a mobile de- vice, key object interactions must be displayed at both sufficient size and spatial detail for easy recognition. The contextual objects in the animation are less important. The premise of our method is that when the key objects are known, their features can be exagger- ated in order to render their interaction more obvious. Objects in vector graphics images and animation are typically uni- formly scaled regardless of their importance. Therefore, we intro- duce a perceptually motivated algorithm that exploits the semantics of vector graphics data to guide the retargeting process. In addi- tion, the algorithm redistributes spatial detail among the objects in the scaled animation based on importance. 1.1 Contributions This work provides tools for artists to intuitively author and manip- ulate machine-readable forms of animation. We also demonstrate that these tools are useful for encoding multiple levels of detail in a single image to enhance the utility of mobile devices as information displays. The intellectual contribution of this work is the idea of importance tags that can be leveraged to make imagery dynamically adapt to a user’s needs. 69 Copyright is held by the HIT Lab NZ, University of Canterbury MUM 2005 Christchurch, New Zealand ISBN 0-473-10658-2