This Article 
   
 Share 
   
 Bibliographic References 
   
 Add to: 
 
Digg
Furl
Spurl
Blink
Simpy
Google
Del.icio.us
Y!MyWeb
 
 Search 
   
Scalable Hybrid Unstructured and Structured Grid Raycasting
November/December 2007 (vol. 13 no. 6)
pp. 1592-1599
This paper presents a scalable framework for real-time raycasting of large unstructured volumes that employs a hybrid bricking approach. It adaptively combines original unstructured bricks in important (focus) regions, with structured bricks that are resampled on demand in less important (context) regions. The basis of this focus+context approach is interactive specification of a scalar degree of interest (DOI) function. Thus, rendering always considers two volumes simultaneously: a scalar data volume, and the current DOI volume. The crucial problem of visibility sorting is solved by raycasting individual bricks and compositing in visibility order from front to back. In order to minimize visual errors at the grid boundary, it is always rendered accurately, even for resampled bricks. A variety of different rendering modes can be combined, including contour enhancement. A very important property of our approach is that it supports a variety of cell types natively, i.e., it is not constrained to tetrahedral grids, even when interpolation within cells is used. Moreover, our framework can handle multi-variate data, e.g., multiple scalar channels such as temperature or pressure, as well as time-dependent data. The combination of unstructured and structured bricks with different quality characteristics such as the type of interpolation or resampling resolution in conjunction with custom texture memory management yields a very scalable system.

[1] I. Boada, I. Navazo, and R. Scopigno, Multiresolution volume visualization with a texture-based octree. The Visual Computer, 17 (3): 185–197, 2001.
[2] S. P. Callahan, L. Bavoil, V. Pascucci, and C. T. Silva, Progressive volume rendering of large unstructured grids. IEEE Transactions on Visualization and Computer Graphics, 12 (5): 1307–1314, 2006.
[3] S. P. Callahan, M. Ikits, J. L. D. Comba, and C. T. Silva, Hardware-assisted visibility sorting for unstructured volume rendering. IEEE Transactions on Visualization and Computer Graphics, 11 (3): 285–295, 2005.
[4] H. Doleisch, M. Gasser, and H. Hauser, Interactive feature specification for focus+context visualization of complex simulation data. In Proc. of the 5th Joint IEEE TCVG - EUROGRAPHICS Symposium on Visualization (VisSym 2003), pages 239–248, 2003.
[5] H. Doleisch and H. Hauser, Smooth brushing for focus+context visualization of simulation data in 3D. In WSCG 2002 Conference Proceedings, pages 147–154, 2002.
[6] C. Everitt, Interactive order-independent transparency, Sept.01 2001.
[7] M. Floater, Mean value coordinates. Computer Aided Geometric Design, 20 (1), 2003.
[8] M. P. Garrity, Raytracing irregular volume data. ACM Computer Graphics, 24 (5): 35–40, 1990.
[9] J. Georgii and R. Westermann, A generic and scalable pipeline for GPU tetrahedral grid rendering. IEEE Trans. Vis. Comput. Graph, 12 (5): 1345–1352, 2006.
[10] M. Hadwiger, C. Sigg, H. Scharsach, K. Buhler, and M. Gross, Real-time ray-casting and advanced shading of discrete isosurfaces. Computer Graphics Forum, 24 (3): 303–312, 2005.
[11] A. Helgeland and O. Andreassen, Visualization of vector fields using seed LIC and volume rendering. IEEE Transactions on Visualization and Computer Graphics, 10 (6): 673–682, 2004.
[12] T. Ju, S. Schaefer, and J. Warren, Mean value coordinates for closed triangular meshes. In Proceedings of SIGGRAPH 2005, pages 561–566, 2005.
[13] M. Kraus and T. Ertl, Cell-projection of cyclic meshes. In Proceedings IEEE Visualization 2001, pages 215–222, 2001.
[14] J. Krüger, J. Schneider, and R. Westermann, ClearView: An interactive context preserving hotspot visualization technique. In Proceedings IEEE Visualization 2006, pages 941–948, 2006.
[15] J. Krüger and R. Westermann, Acceleration techniques for GPU-based volume rendering. In Proceedings IEEE Visualization 2003, pages 287–292, 2003.
[16] E. LaMar, B. Hamann, and K. I. Joy, Multiresolution techniques for interactive texture-based volume visualization. In Proceedings IEEE Visualization '99, pages 355–361, 1999.
[17] T. Langer, A. Belyaev, and H.-P. Seidel, Spherical barycentric coordinates. In Proceedings of Eurographics Symposium on Geometry Processing 2006, pages 81–88, 2005.
[18] J. Leven, J. Corso, J. Cohen, and S. Kumar, Interactive visualization of unstructured grids using hierarchical 3D textures. In Proc. IEEEE Symposium on Volume Visualization 2002 (VolVis 2002), pages 37–44, Oct.28–29 2002
[19] N. Max, P. Williams, C. Silva, and R. Cook, Volume rendering for curvilinear and unstructured grids. In Proc. of Computer Graphics International, pages 210–215, 2003.
[20] S. Parker, M. Parker, Y. Livnat, P.-P. Sloan, C. Hansen, and P. Shirley, Interactive ray tracing for volume visualization. IEEE Transactions on Visualization and Computer Graphics, 5 (3): 238–250, 1999.
[21] S. Röttger, S. Guthe, A. Schieber, and T. Ertl, Convexification of unstructured grids. In Proc. of the 9th Fall Workshop on Vision, Modeling and Visualization (VMV 2004), pages 283–292, 2004.
[22] S. Röttger, M. Kraus, and T. Ertl, Hardware-accelerated volume and iso-surface rendering based on cell-projection. In IEEE Visualization, pages 109–116, 2000.
[23] P. Shirley and A. A. Tuchman, Polygonal approximation to direct scalar volume rendering. In Proceedings San Diego Workshop on Volume Visualization, Computer Graphics, volume 24, pages 63–70, 1990.
[24] C. T. Silva, J. S. B. Mitchell, and P. L. Williams, An exact interactive time visibility ordering algorithm for polyhedral cell complexes. In Proc. IEEE Symposium on Volume Visualization '98 (VolVis '98), pages 87–94, 1998.
[25] C. M. Stein, B. G. Becker, and N. L. Max, Sorting and hardware assisted rendering for volume visualization. In Proc. IEEE Symposium on Volume Visualization '94 (VolVis '94), pages 83–89, 1994.
[26] M. Strengert, M. Magallón, D. Weiskopf, S. Guthe, and T. Ertl, Hierarchical visualization and compression of large volume datasets using GPU clusters. In 5th Eurographics/ACM SIGGRAPH Symposium on Parallel Graphics and Visualization (EGPGV 2004), pages 41–48, 2004.
[27] M. Trenker, H. Lang, P. Muigg, and H. Doleisch, Validation of vortex flow phenomena in electrical machinery using advanced simulation and visualization techniques. In Proceedings of the NAFEMS Worldcongress, page full Proceedings on CDROM, 2007.
[28] D. Uesu, L. Bavoil, S. Fleishman, J. Shepherd, and C. T. Silva, Simplification of unstructured tetrahedral meshes by point sampling. In Volume Graphics, pages 157–165, 2005.
[29] I. Viola, M. Feixas, M. Sbert, and M. E. Gröller, Importance-driven focus of attention. In Proceedings IEEE Visualization 2006, pages 933–940, 2006.
[30] M. Weiler and T. Ertl, Hardware-software-balanced resampling for the interactive visualization of unstructured grids. In Proceedings IEEE Visualization 2001, 2001.
[31] M. Weiler, M. Kraus, M. Merz, and T. Ertl, Hardware-based ray casting for tetrahedral meshes. In Proceedings IEEE Visualization 2003, pages 333–340, 2003.
[32] M. Weiler, M. Kraus, M. Merz, and T. Ertl, Hardware-based view-independent cell projection. IEEE Transactions on Visualization and Computer Graphics, 9 (2): 163–175, 2003.
[33] M. Weiler, P. N. Mallón, M. Kraus, and T. Ertl, Texture-encoded tetrahedral strips. In Proc. IEEE Symposium on Volume Visualization 2004 (VolVis 2004), pages 71–78, 2004.
[34] M. Weiler, R. Westermann, C. D. Hansen, K. Zimmerman, and T. Ertl, Level-of-detail volume rendering via 3D textures. In Proc. IEEE Symposium on Volume Visualization 2000 (VolVis 2000), pages 7–13, 2000.
[35] R. Westermann, The rendering of unstructured grids revisited. In Proc. of the 3rd Joint IEEE TCVG - EUROGRAPHICS Symposium on Visualization (VisSym 2001), pages 65–74, 2001.
[36] P. L. Williams, Visibility-ordering meshed polyhedra. ACM Trans. Graph., 11 (2): 103–126, 1992.
[37] Y. Zhou and M. Garland, Interactive point-based rendering of higher-order tetrahedral data. IEEE Transactions on Visualization and Computer Graphics, 12 (5): 1229–1236, 2006.

Index Terms:
Volume Rendering of Unstructured Grids, Focus+Context Techniques, Hardware-Assisted Volume Rendering
Citation:
Philipp Muigg, Markus Hadwiger, Helmut Doleisch, Helwig Hauser, "Scalable Hybrid Unstructured and Structured Grid Raycasting," IEEE Transactions on Visualization and Computer Graphics, vol. 13, no. 6, pp. 1592-1599, Nov.-Dec. 2007, doi:10.1109/TVCG.2007.70588
Usage of this product signifies your acceptance of the Terms of Use.