1. 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

2. 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

3. 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?

4. 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.

5. CAVASS features ► Image processing ► Visualization ► Manipulation ► Analysis Of large, multidimensional (at least 3D), possibly multimodality, data sets.

6. CAVASS Port Data ImageProcessingVisualizeManipulateAnalyze

7. 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.

8. 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

9. 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

10. An example of overlaid slice display in CAVASS on the Windows operating system.

11. 3D rendering in CAVASS 1. Surface rendering 2. Volume rendering

12. 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)

13. 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

14. 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

15. ► 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

16. ► 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

17. 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

18. Example of triangulated shell (t-shell) rendering in CAVASS on the Windows operating system.

20. Experimental results

21. Description of datasets of varying sizes used in the comparisons.

22. 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.

23. Volume rendering timing comparison for sequential and parallel implementations of CAVASS volume rendering, VTK ray casting, and VTK 2D texture mapped volume rendering.

24. 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.

25. Head mounted display employed by CAVASS for stereo viewing.

26. Parallelism ► Considered:  MPI/OpenMPI ► Message Passing Interface  OpenMP ► Open specifications for Multi Processing

27. 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

28. Parallelism recommendation ► CAVASS uses MPI. YOU ALREADY

29. 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.

30. 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