Advertisement

The Visual Computer

, Volume 26, Issue 6–8, pp 687–695 | Cite as

Volumetric ambient occlusion for volumetric models

  • Marc Ruiz
  • Lázló Szirmay-Kalos
  • Tamás Umenhoffer
  • Imma Boada
  • Miquel Feixas
  • Mateu Sbert
Original Article

Abstract

This paper presents new algorithms to compute ambient occlusion for volumetric data. Ambient occlusion is used in video-games and film animation to mimic the indirect lighting of global illumination. We extend a novel interpretation of ambient occlusion to volumetric models that measures how big portion of the tangent sphere of a surface belongs to the set of occluded points, and propose statistically robust estimates for the ambient occlusion value. The data needed by this estimate can be obtained by separable filtering of the voxel array. As ambient occlusion is meant to obtain global illumination effects, it can provide decisive clues in interpreting the data. The new algorithms obtain smooth shading and can be computed at interactive rates, being thus appropriate for dynamic models exploration.

Keywords

Ambient occlusion Obscurances Volume rendering 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Desgranges, Engel: Fast ambient occlusion for direct volume rendering. US patent application 2007/0013696A1 (2007) Google Scholar
  2. 2.
    Grun, H.: Approximate cumulative distribution function shadow mapping. In: Engel, W. (ed.) Shader X 7. Course Technology (2008) Google Scholar
  3. 3.
    Hernell, F., Ljung, P., Ynnerman, A.: Efficient ambient and emissive tissue illumination using local occlusion in multiresolution volume rendering. In: Eurographics/IEEE-VGTC Symposium on Volume Graphics, pp. 1–8 (2007) Google Scholar
  4. 4.
    Iones, A., Krupkin, A., Sbert, M., Zhukov, S.: Fast, realistic lighting for video games. IEEE Comput. Graph. Appl. 23(3), 54–64 (2003) CrossRefGoogle Scholar
  5. 5.
    Jainek, W., Born, S., Bartz, D., Straßer, W., Fischer, J.: Illustrative Hybrid Visualization and Exploration of Anatomical and Functional Brain Data, pp. 855–862 (2008) Google Scholar
  6. 6.
    Landis, H.: Production-ready global illumination. In: Course 16 Notes, SIGGRAPH 2002 (2002) Google Scholar
  7. 7.
    Méndez-Feliu, Á., Sbert, M., Neumann, L.: Obscurances for ray-tracing. In: EUROGRAPHICS 2003 Poster Presentations. Granada, Spain (2003) Google Scholar
  8. 8.
    Méndez-Feliu, Á., Sbert, M.: From obscurances to ambient occlusion: a survey. Vis. Comput. 25(2), 181–196 (2008) CrossRefGoogle Scholar
  9. 9.
    Neumann, L., Csébfalvi, B., König, A., Gröller, E.: Gradient estimation in volume data using 4d linear regression. Comput. Graph. Forum 19(3), 351–358 (2000) CrossRefGoogle Scholar
  10. 10.
    Penner, E., Mitchell, R.: Isosurface ambient occlusion and soft shadows with filterable occlusion maps. In: IEEE/EG Symposium on Volume and Point-Based Graphics, pp. 57–64 (2008) Google Scholar
  11. 11.
    Ropinski, T., Meyer-Spradow, J., Diepenbrock, S., Mensmann, J., Hinrichs, K.H.: Interactive volume rendering with dynamic ambient occlusion and color bleeding. Comput. Graph. Forum 27(2), 567–576 (2008) CrossRefGoogle Scholar
  12. 12.
    Ruiz, M., Boada, I., Viola, I., Bruckner, S., Feixas, M., Sbert, M.: Obscurance-based volume rendering framework. In: Proceedings of IEEE/EG International Symposium on Volume and Point-Based Graphics, pp. 113–120 (2008) Google Scholar
  13. 13.
    Stewart, A.J.: Vicinity shading for enhanced perception of volumetric data. In: VIS ’03: Proceedings of the 14th IEEE Visualization, pp. 355–362 (2003) Google Scholar
  14. 14.
    Szirmay-Kalos, L., Umenhoffer, T., Toth, B., Szecsi, L., Sbert, M.: Volumetric ambient occlusion for real-time rendering and games. IEEE Comput. Graph. Appl. 30(1), 70–79 (2010) CrossRefGoogle Scholar
  15. 15.
    Winitzki, S.: A handy approximation for the error function and its inverse. http://homepages.physik.uni-muenchen.de/Winitzki/erf-approx.pdf (2008)
  16. 16.
    Wyman, C., Parker, S.G., Shirley, P., Hansen, C.D.: Interactive display of isosurfaces with global illumination. IEEE Trans. Vis. Comput. Graph. 12(2), 186–196 (2006) CrossRefGoogle Scholar
  17. 17.
    Zhukov, S., Iones, A., Kronin, G.: An ambient light illumination model. In: Proceedings of Eurographics Rendering Workshop ’98, pp. 45–56 (1998) Google Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Marc Ruiz
    • 1
  • Lázló Szirmay-Kalos
    • 2
  • Tamás Umenhoffer
    • 2
  • Imma Boada
    • 1
  • Miquel Feixas
    • 1
  • Mateu Sbert
    • 1
  1. 1.Graphics and Imaging LaboratoryUniversitat de GironaGironaSpain
  2. 2.Budapest University of Technology and EconomicsBudapestHungary

Personalised recommendations