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Local Ambient Occlusion in Direct Volume Rendering
Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
Siemens Corporation Research.
Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-9466-9826
2010 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 16, no 4, 548-559 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel technique to efficiently compute illumination for Direct Volume Rendering using a local approximation of ambient occlusion to integrate the intensity of incident light for each voxel. An advantage with this local approach is that fully shadowed regions are avoided, a desirable feature in many applications of volume rendering such as medical visualization. Additional transfer function interactions are also presented, for instance, to highlight specific structures with luminous tissue effects and create an improved context for semitransparent tissues with a separate absorption control for the illumination settings. Multiresolution volume management and GPU-based computation are used to accelerate the calculations and support large data sets. The scheme yields interactive frame rates with an adaptive sampling approach for incrementally refined illumination under arbitrary transfer function changes. The illumination effects can give a better understanding of the shape and density of tissues and so has the potential to increase the diagnostic value of medical volume rendering. Since the proposed method is gradient-free, it is especially beneficial at the borders of clip planes, where gradients are undefined, and for noisy data sets.

Place, publisher, year, edition, pages
IEEE , 2010. Vol. 16, no 4, 548-559 p.
Keyword [en]
Local illumination, volumetric ambient occlusion, volume rendering, medical visualization, emissive tissues, shading, shadowing
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-56687DOI: 10.1109/TVCG.2009.45ISI: 000277650300003OAI: diva2:321233
©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Frida Hernell, Patric Ljung and Anders Ynnerman, Local Ambient Occlusion in Direct Volume Rendering, 2010, IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS, (16), 4, 548-559. Available from: 2010-05-31 Created: 2010-05-31 Last updated: 2015-09-22Bibliographically approved
In thesis
1. Efficient Methods for Volumetric Illumination
Open this publication in new window or tab >>Efficient Methods for Volumetric Illumination
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Modern imaging modalities can generate three-dimensional datasets with a very high detail level. To transfer all the information to the user in an efficient way there is a need for three-dimensional visualization. In order to enhance the diagnostic capabilities the utilized methods must supply the user with fast renderings that are easy to interpret correctly.

It can thus be a challenge to visualize a three-dimensional dataset in a way that allows the user to perceive depth and shapes. A number of stereoscopic solutions are available on the market but it is in many situations more practical and less expensive to use ordinary two-dimensional displays. Incorporation of advanced illumination can, however, improve the perception of depth in a rendering of a volume. Cast shadows provide the user with clues of distances and object hierarchy. Simulating realistic light conditions is, however, complex and it can be difficult to reach interactive frame rates. Approximations and clever implementations are consequently required.

This thesis presents efficient methods for calculation of illumination with the objective of providing the user with high spatial and shape perception. Two main types of light conditions, a single point light source and omni-directional illumination, are considered. Global transport of light is efficiently estimated using local piecewise integration which allows a graceful speed up compared to brute force techniques. Ambient light conditions are calculated by integrating the incident light along rays within a local neighborhood around each point in the volume.

Furthermore, an approach that allows the user to highlight different tissues, using luminous materials, is also available in this thesis. A multiresolution data structure is employed in all the presented methods in order to support evaluation of illumination for large scale data at interactive frame rates.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 59 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1406
National Category
Engineering and Technology
urn:nbn:se:liu:diva-71460 (URN)978-91-7393-041-3 (ISBN)
Public defence
2011-11-25, Wrannesalen, Center for Medical Image Science and Visualization, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Available from: 2011-10-19 Created: 2011-10-19 Last updated: 2015-09-22Bibliographically approved

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