Issue No. 06 - November/December (2010 vol. 16)
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.187
Amel Guetat , University of Strasbourg
Alexandre Ancel , University of Strasbourg
Stéphane Marchesin , UC Davis
Jean-Michel Dischler , 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
J. Dischler, S. Marchesin, A. Ancel and A. Guetat, "Pre-Integrated Volume Rendering with Non-Linear Gradient Interpolation," in IEEE Transactions on Visualization & Computer Graphics, vol. 16, no. , pp. 1487-1494, 2010.