|Interactive Display of Illuminated Field Lines
|The purpose of this project is to take advantage of graphics hardware to do illuminated shading for lines. This is useful for accurately visualizing the 3-D structure of vector field data, especially for large volumes of data. The speed afforded by the exploitation of hardware allows for interactive visualization of large vector field datasets.
Generally there is no concept of shading for lines, which are
after all infinitesimal objects. However, it is possible to give
sensible meaning to this idea by considering the limit of
a shaded cylinder as its radius goes to zero. Such operations
are not supported in standard graphics interfaces. It is
possible though to apply textures to lines.
The basic technique then relies on using the texture map capabilities of the graphics hardware to simulate illumination by light sources. This is done by generating an appropriate texture, and cleverly assigning the texture coordinates for each line vertex. Using the texture transformation matrix one can effictively "trick" the hardware into evaluating the appropriate inner products and use the results to index into the texture. The result is a color returned from the textures which corresponds to the proper lighting illumination effects.
The implementation of the project is done by subclassing OpenInventor. This allows easy manipulation with other predefined OpenInventor primitives such as spheres, polygons, etc.
The results are quite spectacular, but only works well on machines with hardware support for texture mapping. The shaded field lines provide dramatically more visual cues to the structure of the field as compared to conventional solid lines. In addition, transparency shadnig allows greater insight to the field structure in the center of the field.
Download: SoShadedLineSet.tar.gz © Copyright Gary Wu, CS 174c Project 1997
Copyright © 1998 Gary Wu Last modified: Sat Feb 28 15:22:14 PST 1998