Browsing by Subject "Parallel direct volume rendering"

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Open Access
Exploiting replicated data for communication load balancing in image-space parallel direct volume rendering of unstructured grids
(2009) Okuyan, Erkan
The focus of this work is on parallel volume rendering applications in which renderings with different parameters are successively repeated over the same dataset. The only reason for inter-task interaction is the existence of data primitives that are inputs to several tasks. Both computational structure and expected task execution times may change during successive rendering instances. Change in computational structure means change in the data primitive requirements of tasks. Since the individual processors of a parallel system have a limited storage capacity, we can reserve a limited amount of storage for holding replicas at each processor. For the parallelization of a particular rendering instance, the remapping model should utilize the replication pattern of the previous rendering instance(s) for reducing the communication overhead due to the data replication requirement of the current rendering instance. We propose a two-phase model for solving this problem. The hypergraphpartitioning-based model proposed for the first phase aims to minimize the total message volume that will be incurred due to the replication/migration of input data while maintaining balance on computational and receive-volume loads of processors. The network-flow-based model proposed for the second phase aims to minimize the maximum message volume handled by processors via utilizing the flexibility in assigning send-communication tasks to processors, which is introduced by data replication. The validity of our proposed model is verified on image-space parallelization of a direct volume rendering algorithm.
Open Access
Parallel direct volume rendering of unstructured grids based on object-space decomposition
(1997-10) Fındık, Ferit
This work investigates object-space (OS) parallelization of an efficient ray-casting based direct volume rendering algorithm (DVR) for unstructured grids on distributed-memory architectures. The key point for a successful parallelization is to find an OS decomposition which maintains the OS coherency and computational load balance as much as possible. The OS decomposition problem is modeled as a graph partitioning (GP) problem with correct view-dependent node and edge weighting. As the parallel visualizations of the results of parallel engineering simulations are performed on the same machine, OS decomposition, which is necessary for each visualization instance because of the changes in the computational structures of the successive parallel steps, constitutes a typical case of the general remapping problem. A GP-based model is proposed for the solution of the general remapping problem by constructing an augmented remapping graph. The remapping tool RM-MeTiS, developed by modifying and enhancing the original MeTiS package for partitioning the remapping graph, is successfully used in the purposed parallel DVR algorithm. An effective view-dependent cell-clustering scheme is introduced to induce more tractable contracted view-independent remapping graphs for successive visualizations. An efficient estimation scheme with high accuracy is proposed for view-dependent node and edge weighting of the remapping graph. Speedup values as high as 22 are obtained on a Parsytec CC system with 24 processors in the visualization of benchmark volumetric datasets and the proposed DVR algorithm seems to be linearly scalable according to the experimental results.