Sampling and Anti-Aliasing of Discrete 3-D Volume Density Textures

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 position 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. (AGD

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

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

Stylised procedural animation

This thesis develops a stylised procedural paradigm for computer graphics animation. Cartoon effects animations - stylised representations of natural phenomena - have presented a long-standing, difficult challenge to computer animators. We propose a framework for achieving the intricacy of effects motion with minimal animator intervention.Our approach is to construct cartoon effects by simulating the hand-drawing process through synthetic, computational means. We create a system which emulates the stylish appearance, movements of cartoon effects in both 2D and 3D environments. Our computational models achieve this by capturing the essential characteristics common to all cartoon effects: structure modelling, dynamic controlling and stylised rendering.To validate our framework, we have implemented a cartoon effects system for a range of effects including water effects, fire, smoke, rain and snow. Each effect model has its own static structure such as how the different parts are related temporarily. The flexibility of our approach is suggested most evidently by the high-level controls on shape, colour, timing and rendering on the effects. Like their hand-drawn counterparts, they move consistently while retaining the hand-crafted look.Since the movements of cartoon effects are animated procedurally, their detailed motions need not be keyframed. This thesis therefore demonstrates a powerful approach to computer animation in which the animator plays the role of a high level controller, rather than the more conventional hand-drawing slave. Our work not only achieves cartoon effects animation of un-precedented complexity, but it also provides an interesting experimental domain for related research disciplines toward more creative and expressive image synthesis in animation