Carla Maria Dal Sasso Freitas

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<i>Cooperative manipulation</i> refers to the simultaneous manipulation of a virtual object by multiple users in an immersive virtual environment. This paper describes a framework supporting the development of collaborative manipulation techniques, and example techniques we have tested within this framework. We describe the modeling of cooperative(More)
The broad-phase step of collision detection in scenes composed of <i>n</i> moving objects is a challenging problem because enumerating collision pairs has an inherent <i>O(n</i><sup>2</sup>) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we(More)
Information visualization systems often present usability problems mainly because many of these tools are not submitted to complete evaluation studies. This paper presents an experimental study based on tests with users to evaluate two multidimensional information visualization techniques, Parallel Coordinates and Radviz. The tasks used in the experiments(More)
The recent advance of graphics hardware allowed real-time volume rendering of structured grids using a 3D texturing approach. The next challenging problem is to extend the algorithms to time-varying volumetric data (4D functions), which consume more storage and are not directly supported in current graphics hardware. Here we present a new visualization(More)
Several information visualization techniques have been developed in the last few years due to the need of representing and analyzing the huge amount of data generated by several applications or made available through the World Wide Web. These techniques are usually interactive and provided as part of a graphical user interface. Information visualization(More)
Direct volume rendering techniques allow visualization of volume data without extracting intermediate geometry. The mapping from voxel attributes to optical properties is performed by transfer functions which, consequently, play a crucial role in building informative images from the data. One-dimensional transfer functions, which are based only on a scalar(More)
This paper describes a new joint model for articulated human skeletons. The model is based in human anatomy and was conceived for use in medical applications. In this model, we try to overcome some limitations of other models used in computer graphics. To validate, we compared a knee modeled with our approach with a simulator, a plastic model of a knee, and(More)
The design of multidimensional visualization techniques is based on the assumption that a graphical representation of a large dataset can give more insight to a user, by providing him/her a more intuitive support in the process of exploiting data. When developing a visualization technique, the analytic and exploratory tasks that a user might need or want to(More)