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CAVASS - Visualization Aspects George Grevera a,b, Jayaram Udupa b, Dewey Odhner b, Ying Zhuge b, Andre Souza b, Tad Iwanaga b, and Shipra Mishra b a Department of Mathematics and Computer Science, Saint Joseph’s University, 5600 City Avenue, Philadelphia, PA 19131 b Medical Image Processing Group (MIPG), Department of Radiology, University of Pennsylvania, 423 Guardian Drive, 4th Floor Blockley Hall, Philadelphia, PA 19104-6021
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What is CAVASS? ► A CAVA Software System ► What is CAVA? Computer Assisted Visualization and Analysis ► So CAVASS is a Computer Assisted Visualization and Analysis Software System
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What is CAVASS? ► Next generation of 3DVIEWNIX. development started in 1987 released in 1993 development dates back to the ’70s free runs on Unix and subsequently Linux 60 person years of effort distributed to 100s of sites basis for over 15 specialized packages/apps Why CAVASS?
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Significant, more recent developments 1. PC platform matures. price spirals downward performance increases dramatically supplant Unix as the scientific workstation of choice 2. Network bandwidth greatly increases. 3. Useable parallel processing standards are defined and become freely available. 4. Toolkits such as VTK and ITK become freely available. 5. GUI concept matures and platform independent libraries are developed.
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CAVASS features ► Image processing ► Visualization ► Manipulation ► Analysis Of large, multidimensional (at least 3D), possibly multimodality, data sets.
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CAVASS Port Data ImageProcessingVisualizeManipulateAnalyze
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Key CAVASS features ► Built upon our experience with 3DVIEWNIX. ► Leverages the existing 3DVIEWNIX software base and user interface. ► Port to Windows and Mac OS with continued support for Unix and Linux. ► Implement parallel algorithms for time consuming operations. ► Support for stereo rendering. ► Interface to ITK.
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Other CAVASS related presentations ► 6509-66 in Visualization Conference: Image Processing Aspects ► 6519-07 in PACS Conference: Software Overview ► Software Workshop, Sunday at 5:15PM
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Visualization and CAVASS ► All of the most popular modes of visualization are incorporated into CAVASS. various 2D slice modes reslicing MIP surface rendering volume rendering animation
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An example of overlaid slice display in CAVASS on the Windows operating system.
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3D rendering in CAVASS 1. Surface rendering 2. Volume rendering
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3D rendering in CAVASS ► Surface rendering utilizes digital shell and triangulated shell (t- shell) rendering algorithms operates 6 to 30 times faster entirely in software than hardware-based rendering implemented only in sequential and not parallel mode (because of their existing high speed)
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3D rendering in CAVASS ► Volume rendering based on shell rendering implemented in parallel mode compared to the implementation in VTK CAVASS operates at least as fast as VTK and often achieves superior performance by a factor of 1.5 to 5
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Volume Visualization ► surface rendering typically binary explicit surface geometric primitives ► volume rendering employs some classification (transfer) function no explicit surface no geometry ► shell rendering some classification fuzzy surface surface normals
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► Udupa, & Odhner, 1991 binary shell defined ► Udupa, & Odhner, 1993 fuzzy shell defined ► Olstad, Steen, & Halaas, 1995 VLSI architecture for shell rendering ► Carnielli, Falcao, & Udupa, 1998 perspective projection introduced ► Grevera, Udupa, & Odhner, 1999 S/R renders surfaces in software 18 to 31 times faster than hardware ► Grevera, Udupa, & Odhner, 2000 S/R renders volumes in software at nearly the same speed of volume rendering hardware ► Grevera, Udupa, & Odhner, 2001 T-shell rendering introduced software/hardware hybrid reduce triangles sent to graphics pipeline ► Grevera, Udupa, & Odhner, 2005 T-shell rendering entirely in software 2-10x faster than hardware Shell Rendering
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► parallel projection ► FTB/BTF voxel projection (no ray casting) ► takes advantage of medical data: regular, cuboidal nature of voxels closed surfaces ► combines surface and volume rendering
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T-shell ► not a decimation method; retains full detail ► hardware takes a long time to render the first view 50-2000 times longer than t-shell rendering ► hardware fails to render more than 6 million triangles T-shell rendering has no such limitation ► T-shell rendering is about 2-10 times faster than the hardware method
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Example of triangulated shell (t-shell) rendering in CAVASS on the Windows operating system.
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Experimental results
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Description of datasets of varying sizes used in the comparisons.
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Surface rendering timing comparison for CAVASS shell rendering (sequential implementation with and without antialiasing) and surface rendering as implemented in VTK. Note: Same input triangulated surface.
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Volume rendering timing comparison for sequential and parallel implementations of CAVASS volume rendering, VTK ray casting, and VTK 2D texture mapped volume rendering.
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Portable graphics user interface ► Considered Qt, wxWidgets (formerly wxWindows), and FLTK. Qt – proprietary, closed, fees FLTK – free but doesn’t maintain native look- and-feel wxWidgets ► one C++ API for all OS’s ► maintains native look-and-feel ► free, open source, multiplatform ► portable support for threads, copy-paste, drag-and- drop, print, etc.
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Head mounted display employed by CAVASS for stereo viewing.
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Parallelism ► Considered: MPI/OpenMPI ► Message Passing Interface OpenMP ► Open specifications for Multi Processing
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Parallelism ► MPI free (for both Windows, Linux, and Unix) part of base Linux install COW (cluster of workstations model) leverages existing hardware/computers optional, inexpensive network upgrade ► OpenMP requires purchase of specialized compilers “multi-threaded, shared memory parallelism” model requires purchase of expensive multiprocessor systems
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Parallelism recommendation ► CAVASS uses MPI. YOU ALREADY
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Thanks for your attention! ► CAVASS is available from www.mipg.upenn.edu/~cavass. ► Release date: July/August 2007. ► The authors gratefully acknowledge NIH grant number R01-EB004395-01 for support of this work.
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Other CAVASS related presentations ► 6509-66 in Visualization Conference: Image Processing Aspects ► 6519-07 in PACS Conference: Software Overview ► Software Workshop, Sunday at 5:45 PM
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