Section: Application Domains

Virtual Reality

Participants : Thierry Gautier, Bruno Raffin, Jean-Louis Roch.

We are pursuing and extending existing collaborations to develop virtual reality applications on PC clusters and grid environments:

• Real time 3D modeling. An on-going collaboration with the MORPHEO project focuses on developing solutions to enable real time 3D modeling from multiple cameras using a PC cluster. This work is tightly coupled to the FlowVR software. Our recent developments take two main directions:

  • to provide the user a high level of interaction and immersion in the mixed reality environment. This work is focused on the Grimage platform and its successor, the new equipex Kinovis managed by Morpheo team. The camera position and orientation need to be precisely known at anytime, requiring to develop on-line calibration approaches. The background subtraction cannot anymore be based on a static background learning for the mobile camera, required here too new algorithms.

  • Distributed collaboration across distant sites. In the context of the ANR DALIAn we have developped a collaborative application where multiple users, distributed in several sites each using a real time 3D modeling platform, can meet in a virtual world with a user in Grenoble also using a similar platform. The main issues are related to data transfers that need to be carefully managed to ensure a good latency while keeping a good quality, and the development of new interaction paradigms. Focusing on distributed scientific simulation, we extend those technologies in the context of the FVNANO and PetaFlow contracts.

• Real time physical simulation. We are collaborating with the Imagine project on the SOFA simulation framework. Marie Durand a Ph.D. co-advised by François Faure (IMAGINE) and Bruno Raffin, works on parallelizing SOFA using the KAAPI programming environment. The challenge is to provide SOFA with a parallelization that is efficient (real-time) while not being invasive for SOFA programmers (usually not parallel programmer). We developed a first version using the Kaapi environment for SMP machines that relies on a mix of work-stealing and dependency graph analysis and partitioning. A second version targets machines with multiples CPUs and multiple GPUs. We extended the initial framework to support a work stealing based load balancing between CPUs and GPUs. It required to extend Kaapi to support heterogeneous tasks (GPU and CPU ones) and to adapt the work stealing strategy to limit data transfers between CPUs and GPUs (the main bottleneck for GPU computing).

• Distant collaborative work. We conduct experiments using FlowVR for running applications on Grid environments. Two kinds of experiments will be considered: collaborative work by coupling two or more distant VR environments ; large scale interactive simulation using computing resources from the grid. For these experiments, we are collaborating with the LIFO and the LABRI.

• Parallel cache-oblivious algorithms for scientific visualization. In collaboration with the CEA DAM, we have developed a cache-oblivious algorithm with provable performance for irregulars meshes. Based on this work, we are studying parallel algorithms that take advantage of the shared cache usually encountered on multi-core architectures (L3 shared cache) and of harware accelerators. In collaboration with EDF, we develop new parallel algorithms for scientific vizualization (eg VTK) on multicore (phD thesis of Mathias Ettinger). We are also considering adaptive algorithms to take advantage of the new trend of computers to integrate several computing units that may have different computing abilities (multicore arithmetic and graphical processing units, eventually integrated on one chip). We study balancing workload on multi GPU and CPU architectures for scientific visualization problems.