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Illumination-Driven Opacity Modulation for Expressive Volume Rendering

Balázs Csebfalvi, Balázs Tóth, Stefan Bruckner, M. Eduard Gröller

CONFERENCE PAPER: In Proceedings of VMV 2012, pp. 103–109, 2012. DOI: 10.2312/PE/VMV/VMV12/103-109

Abstract

Using classical volume visualization, typically a couple of isosurface layers are rendered semi-transparently to show the internal structures contained in the data. However, the opacity transfer function is often difficult to specify such that all the isosurfaces are of high contrast and sufficiently perceivable. In this paper, we propose a volumerendering technique which ensures that the different layers contribute to fairly different regions of the image space. Since the overlapping between the effected regions is reduced, an outer translucent isosurface does not decrease significantly the contrast of a partially hidden inner isosurface. Therefore, the layers of the data become visually well separated. Traditional transfer functions assign color and opacity values to the voxels depending on the density and the gradient. In contrast, we assign also different illumination directions to different materials, and modulate the opacities view-dependently based on the surface normals and the directions of the light sources, which are fixed to the viewing angle. We will demonstrate that this model allows an expressive visualization of volumetric data.

Published

Proceedings of VMV 2012

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BibTeX

@INPROCEEDINGS{Csebfalvi-2012-IOM,
  author = {Bal{\'a}zs Csebfalvi and Bal{\'a}zs T{\'o}th and Stefan Bruckner
	and M. Eduard Gr{\"o}ller},
  title = {Illumination-Driven Opacity Modulation for Expressive Volume Rendering},
  booktitle = {Proceedings of VMV 2012},
  year = {2012},
  pages = {103--109},
  month = nov,
  abstract = {Using classical volume visualization, typically a couple of isosurface
	layers are rendered semi-transparently to show the internal structures
	contained in the data. However, the opacity transfer function is
	often difficult to specify such that all the isosurfaces are of high
	contrast and sufficiently perceivable. In this paper, we propose
	a volumerendering technique which ensures that the different layers
	contribute to fairly different regions of the image space. Since
	the overlapping between the effected regions is reduced, an outer
	translucent isosurface does not decrease significantly the contrast
	of a partially hidden inner isosurface. Therefore, the layers of
	the data become visually well separated. Traditional transfer functions
	assign color and opacity values to the voxels depending on the density
	and the gradient. In contrast, we assign also different illumination
	directions to different materials, and modulate the opacities view-dependently
	based on the surface normals and the directions of the light sources,
	which are fixed to the viewing angle. We will demonstrate that this
	model allows an expressive visualization of volumetric data.},
  doi = {10.2312/PE/VMV/VMV12/103-109},
  event = {VMV 2012},
  keywords = {illustrative visualization, illumination, volume rendering},
  location = {Magdeburg, Germany},
  url = {http://www.cg.tuwien.ac.at/research/publications/2012/Csebfalvi-2012-IOM/}
}






 Last Modified: Stefan Bruckner, 2014-09-22