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Issue No.06 - November/December (2010 vol.16)
pp: 1487-1494
Alexandre Ancel , University of Strasbourg
Amel Guetat , University of Strasbourg
Shading is an important feature for the comprehension of volume datasets, but is difficult to implement accurately. Current techniques based on pre-integrated direct volume rendering approximate the volume rendering integral by ignoring non-linear gradient variations between front and back samples, which might result in cumulated shading errors when gradient variations are important and / or when the illumination function features high frequencies. In this paper, we explore a simple approach for pre-integrated volume rendering with non-linear gradient interpolation between front and back samples. We consider that the gradient smoothly varies along a quadratic curve instead of a segment in-between consecutive samples. This not only allows us to compute more accurate shaded pre-integrated look-up tables, but also allows us to more efficiently process shading amplifying effects, based on gradient filtering. An interesting property is that the pre-integration tables we use remain two-dimensional as for usual pre-integrated classification. We conduct experiments using a full hardware approach with the Blinn-Phong illumination model as well as with a non-photorealistic illumination model.
direct volume rendering, pre-integration, gradient interpolation
Alexandre Ancel, Stéphane Marchesin, Amel Guetat, "Pre-Integrated Volume Rendering with Non-Linear Gradient Interpolation", IEEE Transactions on Visualization & Computer Graphics, vol.16, no. 6, pp. 1487-1494, November/December 2010, doi:10.1109/TVCG.2010.187
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