To visualize three-dimensional vector fields it is often necessary to depict three-dimensional lines, for example stream lines. Since lines in 3D do not have a unique normal vector, they either have to be flat shaded, impairing the spatial impression of the image, or polygonal tubes have to be used, limiting the number of streamlines that can be displayed in a scene. Another approach would be to use Line Integral Convolution [1, 14], a commonly used algorithm for visualizing vector fields, which is easily extended to 3D. Unfortunately, the results are not as good as in 2D [2], too many details obscure the flow topology. Below three approaches are described which depict lines in three-dimensional space. The first illuminates streamlines, the second tries to ray-cast vector fields and the third describes some strategies to enhance 3D Line Integral Convolution.