Issues on Displaying 3D Data for Scientific Visualization Thomas Theußl theussl@cg.tuwien.ac.at Institute of Computer Graphics Vienna University of Technology Vienna, Austria

Principal Direction-driven 3D LIC textures

Although the results achieved with the method described in Section 3.3 are quite good, the modelling of the ``slabs'' as geometric objects is not satisfying. Furthermore, these ``slabs'' have to be recomputed for each isosurface out of the same set of data, which is cumbersome in cases where it is necessary to view not one but multiple level surfaces through a volume distribution.
Interrante [4] proposes a method where the set of principal directions and principal curvatures is used to define a natural flow over the surface of an object. Since the first principal direction is tangential to the surface with direction of the strongest curvature, each stream line will lie on an isosurface aligned to the curvature of this surface. The set of principal directions can be precomputed for the whole dataset and via 3D Line Integral Convolution it is now possible to generate a solid stroke texture that illustrates the essential shape information of any level surface in the data.
Figure 7 compares a transparent surface to a surface with a texture generated via 3D Line Integral Convolution and the set of principal directions applied, Figure 8 depicts a series of six surfaces textured by the same method.

  
Figure 7: Transparent surface on the left and the same surface on the right with a texture applied generated via principal direction-driven 3D Line Integral Convolution

  
Figure 8: A series of six level surfaces with the same texture applied generated via 3D Line Integral Convolution and the set of principal directions.