IPT & EGVE Workshop (2005) R. Blach, E. Kjems (Editors) IntenSelect: Using Dynamic Object Rating for Assisting 3D Object Selection Gerwin de Haan, Michal Koutek and Frits H. Post Data Visualization Group, http://visualization.tudelft.nl Faculty of Electrical Engineering, Mathematics and Computer Science Delft University of Technology, The Netherlands Abstract We present IntenSelect, a novel selection technique that dynamically assists the user in the selection of 3D objects in Virtual Environments. Ray-casting selection is commonly used, although it has limited accuracy and can be problematic in more difficult situations where the intended selection object is occluded or moving. Selection-by- volume techniques, which extend normal ray-casting, provide error tolerance to cope with the limited accuracy. However, these extensions generally are not usable in the more complex selection situations. We have devised a new selection-by-volume technique to create a more flexible selection technique which can be used in these situations. To achieve this, we use a new scoring function to calculate the score of objects, which fall within a user controlled, conic selection volume. By accumulating these scores for the objects, we obtain a dynamic, time-dependent, object ranking. The highest ranking object, or active object, is indicated by bending the otherwise straight selection ray towards it. As the selection ray is effectively snapped to the object, the user can now select the object more easily. Our user tests indicate that IntenSelect can improve the selection performance over ray-casting, especially in the more difficult cases of small objects. Furthermore, the introduced time-dependent object ranking proves especially useful when objects are moving, occluded and/or cluttered. Our simple scoring scheme can be easily extended for special purpose interaction such as widget or application specific interaction functionality, which creates new possibilities for complex interaction behavior. Categories and Subject Descriptors (according to ACM CCS): H 5.2 [User Interfaces]: Interaction Styles; I 3.6 [Methodology and Techniques]: Interaction Techniques; I 3.7 [Three-Dimensional Graphics and Realism]: Virtual Reality 1. Introduction Virtual Environments have the potential to increase the in- sight into complex multi-dimensional models and processes from a wide range of applications. However, VR applica- tions still are not as widespread as their potential would let us expect. The lack of its general acceptance and use is often attributed to the limited flexibility and practical usefulness of the user interface, even though this is considered as an ad- vantage of VR. One of the most basic elements in the com- plete taxonomy [BWCL01] of three-dimensional interaction is that of object selection. That is, indicating one specific ob- ject in the virtual world. When examined very closely, even this basic task of object selection is often surprisingly diffi- cult and can be a source of irritation for the users. We there- fore believe that the practical usefulness and acceptance of a wide range of interactive VR applications heavily relies on effective selection techniques. We mainly employ Virtual Reality techniques as a mean for enhancing the interactive process of scientific visualiza- tion and data exploration. In addition to rendering techniques for large datasets, we concentrate on one of the main chal- lenges of scientific visualization in VR as described in the overview by Van Dam et. al.: "... to make interaction com- fortable, fast, and effective" [DFL * 00]. Currently our main VR applications focus on the visualization and control of (real-time) simulations of physical processes. We often have to deal with objects dynamically moving through the dataset, such as atoms or glyphs (see Figure 1). The researchers in- c  The Eurographics Association 2005.