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)
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)
Figure 1: Three time instances of a volumetric fluid decompressed and visualized using the fragment shader. Abstract 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(More)
Evaluating user interfaces is usually accomplished to detect design problems in layout and interaction. One possible way to evaluate image quality in computer graphics is visual inspection by experts. Information visualization techniques are usually presented showing their use in experimental situations, employing some kind of analysis. Nevertheless, few(More)
Cooperative manipulation refers to the simultaneous manipulation of a virtual object by multiple users in an immersive virtual environment (VE). In this work, we present techniques for cooperative manipulation based on existing single-user techniques. We discuss methods of combining simultaneous user actions, based on the separation of degrees of freedom(More)
Navigation, object selection and manipulation in virtual environments are based on interaction methods or techniques driven by conventional or special devices. There are a number of techniques and devices available for the development of applications involving interaction in immersive worlds, and to choose the most suitable one for a given situation is a(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)