Advances in the physical sciences have progressively delivered ever increasing,already extremely large data sets to be analyzed. High performance volume renderinghas become critical to the scientists for a better understanding of the massive amountsof data to be visualized. Cluster based rendering systems have become the base lineto achieve the power and flexibility required to perform such task. Furthermore,display arrays have become the most suitable solution to display these data sets attheir natural size and resolution which can be critical for human perception andevaluation.The work in this thesis aims at improving the scalability and usability of volumerendering systems that target visualization on display arrays. The first part dealswith improving the performance by introducing the implementations of two parallelcompositing algorithms for volume rendering: direct send and binary swap. TheHigh quality Volume Rendering (HVR) framework has been extended to accommodateparallel compositing where previously only serial compositing was possible. Thepreliminary results show improvements in the compositing times for direct send even for a small number of processors. Unfortunately, the results of binary swap exhibita negative behavior. This is due to the naive use of the graphics hardware blendingmechanism. The expensive transfers account for the lengthy compositing times.The second part targets the development of scalable and intuitive interactionmechanisms. It introduces the development of a new client application for multitouchtablet devices, like the Apple iPad. The main goal is to provide the HVR framework,that has been extended to use tiled displays, a more intuitive and portable interactionmechanism that can get advantage of the new environment. The previous client isa PC application for the typical desktop settings that use a mouse and keyboard assources of interaction. The current implementation of the client lets the user steerand change the opacity transfer function of the visualization via simple multitouchgestures. Nonetheless, the user can freely move around, engage into discussion withother users and easily pass the tablet around for others to use. Before, this wasnot possible with the same ease of use. Ultimately, the collaborative possibilities are many and extremely interesting to explore.
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