Efficient Visibility Encoding for Dynamic Illumination in Direct Volume Rendering: -
2012 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 18, no 3, 447-462 p.Article in journal (Refereed) Published
We present an algorithm that enables real-time dynamic shading in direct volume rendering using general lighting, includingdirectional lights, point lights and environment maps. real-time performance is achieved by encoding local and global volumetricvisibility using spherical harmonic (SH) basis functions stored in an efficient multi-resolution grid over the extent of the volume. Ourmethod enables high frequency shadows in the spatial domain, but is limited to a low frequency approximation of visibility and illuminationin the angular domain. In a first pass, Level Of Detail (LOD) selection in the grid is based on the current transfer function setting.This enables rapid on-line computation and SH projection of the local spherical distribution of visibility information. Using a piecewiseintegration of the SH coefficients over the local regions, the global visibility within the volume is then computed. By representing thelight sources using their SH projections, the integral over lighting, visibility and isotropic phase functions can be efficiently computedduring rendering. The utility of our method is demonstrated in several examples showing the generality and interactive performanceof the approach.
Place, publisher, year, edition, pages
IEEE , 2012. Vol. 18, no 3, 447-462 p.
Volumetric Illumination, Precomputed Radiance Transfer, Volume Rendering
National CategoryOther Computer and Information Science
IdentifiersURN: urn:nbn:se:liu:diva-66839DOI: 10.1109/TVCG.2011.35ISI: 000299281700010OAI: oai:DiVA.org:liu-66839DiVA: diva2:405088
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Joel Kronander, Daniel Jönsson, Joakim Löw, Patric Ljung, Anders Ynnerman and Jonas Unger, Efficient Visibility Encoding for Dynamic Illumination in Direct Volume Rendering, 2011, IEEE Transactions on Visualization and Computer Graphics.