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Computing Architectures for Virtual Reality

High performance 3D rendering toolkit. Use of multiple CPUs, Use of multiple graphics ... Sepia 2. reads back the framebuffer and distributes it over a fast network (ServerNet II) ...

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Computing Architectures for Virtual Reality

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    1. Computing Architectures for Virtual Reality Multiprocessor Servers / Graphic Supercomputers vs. PC Clusters Architecture

    2. Introduction VR requires: fast graphics and haptics refresh rates? graphic pipelines low latencies? interactivity

    3. Graphics Rendering Pipeline Three functional stages Application stage (SW) Geometry stage (HW) Rasterizer stage (HW)

    4. Computing Architectures (1) Single Host Multiprocessor Server Massively parallel architecture Multiprocessor?interprocessor communication?shared memory pool Multipipe graphics?parallel rendering?bus based fast communication

    5. Computing Architectures (2) Distributed Cluster off-the-shelf hardware interconnecting network scalable

    6. Distributed VR system architecture problems No shared memory pool? low latency network Independent graphic accelerator cards? video signal synchronization If tiled image rendering? composition

    7. Single Host Multiprocessor Multipipe Servers SGI InfiniteReality massively parallel architecture bus-based broadcast communication to distribute primitives Graphics subsystem: Geometry engine, Raster Manager, Display generator

    8. SGI InfiniteReality (1)

    9. SGI InfiniteReality (2)

    10. SGI Performer (1) High performance 3D rendering toolkit Use of multiple CPUs, Use of multiple graphics pipelines

    11. SGI Performer (2) - Multiprocessing Each stage of the graphics pipeline process can then run as a separate process on a separate CPU APP CULL DRAW

    12. SGI Performer (3) - Multichannels Each rendering pipelinecan render multiplechannels – multiple video outputs

    13. SGI Performer (4) - Multipipes Multiple displays synchronized with genlock

    14. SGI Performer (5) - Hyperpipe Temporal Decomposition To use with DPLEX ring or chain

    15. SGI Performer (5) - Frame Synchronization pfSync synchronizes the graphics pipeline to the frame rate DRAW time overruns is specified by the phase control? scene management: LOD, culling, …

    16. PC Cluster Architecture (1) Each node must have access to the same entire data set real time visualization and interactivity ? network latency the seamless, synchronized graphic display (image reassembly)

    17. PC Cluster Architecture (2) 3 levels of synchronization: video signal synchronization? genlock dynamic data synchronization? network frame completion synchronization? swapbuffers barrier

    18. PC Cluster Architecture (3) Display szenarios

    19. PC Cluster Architecture (4) 3DLabs

    20. PC Cluster Architecture - Networks (1) Hardware Solutions Giga Ethernet (1 Gigabit/s, half duplex) Myrinet (2 + 2 Gigabit/s full duplex) ServerNet II (Compaq), ... Software Interfaces TCP / IP PVM, MPI, ...

    21. PC Cluster Architecture - Networks (2) Myrinet massively parallel processors (MPP) communication technology? specialized communication channels, cut-through switches, host interfaces? "OS bypass" for low-latency communication

    22. PC Cluster Architecture - Synchronization (1) The following is required to provide a seamless image: each channel must render the same data pixel rates must be identical the displays must start new images at the same time swapping of their buffers during the same blanking period

    23. PC Cluster Architecture - Synchronization (2) Video Signal Synchronization Genlock:pixel level synchronization is ensured by all graphic pipelines via an (external) sync signal? most precise way Framelock:synchronizes once per frame at the end of the blanking period

    24. PC Cluster Architecture - Synchronization (3) Dynamic Data Synchronization 2 types of changing data control information: direction of view changing / dynamic data set information: model movement 3 approaches for distribution: distribute stimuli calculate resulting data centrally and distribute calculate end graphics data centrally and distribute

    25. PC Cluster Architecture - Synchronization (4) Frame Completion Synchronization: nodes have to wait until are ready to swap buffers? swap barrier synchronization Multiview:

    26. PC Cluster Architecture - Synchronization (5) Net Juggler and SoftGenLock based on an ”input event level” parallelization? No highbandwidth network necessary Synchronization: Real time Linux Fast sync network: PAPERS (Parallel Port - 4µs )

    27. PC Cluster Architecture - Composition (1) Display Reassembly in Hardware Lightning-2 connects to graphic accelerators via DVI any pixel data generated from any node to be dynamically mapped to any location on any display Sepia 2 reads back the framebuffer and distributes it over a fast network (ServerNet II)

    28. PC Cluster Architecture - Composition (2) Lightning-2 Pixel Mapping? strip header Frame transfer protocol? RS232 back connect for sync Image composition Tiled images Colour keying Depth compositing PC Cluster Architecture - Composition (1)PC Cluster Architecture - Composition (1)

    29. PC Cluster Architecture - Composition (3) Lightning-2 Architecture

    30. Single Multipipe Graphics Accelerator (1) Wildcat III 6210 / Wildcat II 5110

    31. Single Multipipe Graphics Accelerator (2)

    32. Single Multipipe Graphics Accelerator (3) ParaScale Architecture

    33. Commercial Cluster Solutions SGI Graphics Cluster™ ImageSync DataSync

    34. Commercial Cluster Solutions Evans & Sutherland – SimFUSION

    35. Commercial Cluster Solutions AEC – ArsBox nodes via Parallelport synchronized Redhat 7.1 SGI Performer 100Mbit Ethernet

    36. Conclusion Graphic Supercomputers Massively parallel structure Expensive Established PC clusters Off-the-shelf hardware Distributed ? synchronization

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