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Sampling and anti-aliasing of discrete 3-D volume density textures

: Gerth, M.; Sakas, G.

Post, F.H.:
Eurographics '91. Proceedings of the European Computer Graphics Conference and Exhibition
Amsterdam: North-Holland Publishing, 1991
ISBN: 0-444-89096-3
Eurographics <12, 1991, Wien>
Conference Paper
Fraunhofer IGD ()
3-D texturing; anti-aliasing; constant-time filtering; density objects; sampling; volume densities; voxel fields

In recent years, a number of techniques have been developed for rendering volume effects (haze, fog, smoke, clouds, etc.) in order to enhance reality in computer-generated imagery as well as to improve the performance of flying, ship, and driving optical simulators. For modeling such effects, volume 'density' objects are used, which are defined by their density distribution in 3-D space. For such a description a three-dimensional voxel field (solid texture) is usually used. Since we deal with 3-D textures, the methods used for sampling 2-D pixel fields cannot always be employed. In this paper, we propose two variants of a new technique for sampling and anti-aliasing 3-D density voxel fields. First, we point out the problems which occur when such 3-D textures are sampled, especially when the point sampling Monte-Carlo method is used. 'Distance sampling'and 'pyramidal-volume sampling'are then introduced. The first technique samples the texture along a straight line defined by the eye pos ition and the pixel midpoint, whereas the pyramidal-volume technique approximately samples the volume of the pyramid defined by the eye and the four pixel corners. In comparison to other existing methods, both methods greatly reduce aliasing and calculation time. Especially the second one provides a constant-time filtering, wherebyminimizing the number of texture evaluations. In the last paper section we demonstrate the applicability of the proposed methods for animation as well as for visualization purposes.