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Parallel Visualization

Parallel Visualization. Kenneth Moreland Sandia National Laboratories. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. Read.

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Parallel Visualization

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  1. Parallel Visualization Kenneth Moreland Sandia National Laboratories Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Read Isosurface Reflect Render The Parallel Visualization Pipeline

  3. Read Read Read Read Isosurface Isosurface Isosurface Isosurface Reflect Reflect Reflect Reflect Render Render Render Render The Parallel Visualization Pipeline

  4. Data Parallel Pipelines • Duplicate pipelines run independently on different partitions of data.

  5. Data Parallel Pipelines • Duplicate pipelines run independently on different partitions of data.

  6. Data Parallel Pipelines • Some operations will work regardless. • Example: Clipping.

  7. Data Parallel Pipelines • Some operations will work regardless. • Example: Clipping.

  8. Data Parallel Pipelines • Some operations will work regardless. • Example: Clipping.

  9. Data Parallel Pipelines • Some operations will have problems. • Example: External Faces

  10. Data Parallel Pipelines • Some operations will have problems. • Example: External Faces

  11. Data Parallel Pipelines • Ghost cells can solve most of these problems.

  12. Data Parallel Pipelines • Ghost cells can solve most of these problems.

  13. Data Partitioning • Partitions should be load balanced and spatially coherent.

  14. Data Partitioning • Partitions should be load balanced and spatially coherent.

  15. Data Partitioning • Partitions should be load balanced and spatially coherent.

  16. Load Balancing/Ghost Cells • Automatic for Structured Meshes. • Partitioning/ghost cells for unstructured is “manual.” • Use the D3 filter for unstructured • (Filters → Alphabetical → D3)

  17. Partitioning on Spatial Structure: K-D Tree

  18. K-D Trees Provide Query Structures What elements are closest to here?

  19. Reconstructing Connectivity Information May not be unique. Neighbor info usually missing.

  20. Read Read Read Read Isosurface Isosurface Isosurface Isosurface Reflect Reflect Reflect Reflect Render Render Render Render The Parallel Visualization Pipeline

  21. Parallel Rendering

  22. Parallel Rendering

  23. Tiled Displays

  24. Rendering Translucent Geometry

  25. Unstructured Volume Rendering in Parallel

  26. Unstructured Volume Rendering in Parallel

  27. Unstructured Volume Rendering in Parallel

  28. Unstructured Volume Rendering in Parallel

  29. Unstructured Volume Rendering in Parallel

  30. Mesh Partitioning

  31. 8 4 7 1 5 6 2 3 K-D Trees Provide Query Structures What is the visibility order of the regions from this viewpoint?

  32. ParaView Architecture for Interactive Remote Parallel Visualization • Three Tier • Data Server • Render Server • Client

  33. Client Data Server Render Server Standalone

  34. Data Server Render Server Client Client-Server Socket

  35. Data Server Render Server Client Client-Render Server-Data Server Socket × N Socket

  36. Data Server Render Server Client Client-Server Socket Minimize Communication Render Remotely Send Images

  37. Rendering Modes • Still Render • Full detail render. • Interactive Render • Sacrifices detail for speed. • Provides quick rendering rate. • Used when interacting with 3D view.

  38. Original Data Divisions: 50x50x50 Divisions: 10x10x10 Level of Detail (LOD) • Geometric decimation. • Used only with Interactive Render

  39. Image Size LOD • ParaView’s parallel rendering overhead proportional to image size. • To speed up interactive rendering, ParaView can render smaller sized images and inflate them. Original Data Subsample Rate: 2 pixels Subsample Rate: 4 pixels Subsample Rate: 8 pixels

  40. Color Depth LOD • Squirt is used to transfer images from server to client. • Squirt is a run length encoder optimized for images. • Run lengths improved by masking out some color bits. 24-bit mask 19-bit mask 10-bit mask

  41. Summary • Most visualization algorithms are embarrassingly parallel. • Ghost cells can eliminate need for communication. • Simulation dumps are often missing connectivity information. • Geometry sizes grow quickly, image sizes don’t. • Sort-last rendering scales well in this regard. • Avoid bottlenecks caused by saturating any process with geometry. • Remote interactivity is important. • Parallel resources are seldom local. • Interactivity can be maintained with levels of detail. • Always be clear what you are using. • Make sure the full detail shows up eventually.

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