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Animation of Orthogonal Texture Patterns for Vector Field Visualization

This website presents additional material accompanying the IEEE Transactions on Visualization and Computer Graphics paper "Animation of Orthogonal Texture Patterns for Vector Field Visualization" by Sven Bachthaler and Daniel Weiskopf.
The videos are captured from the software that was implemented for this paper. It is important to mention that the perception of the animated flow depends on the viewing distance to the monitor. This is due to the fact that the spatial frequency of the line pattern increases when the viewing distance is increased.


This paper introduces orthogonal vector field visualization on 2D manifolds: a representation by lines that are perpendicular to the input vector field. Line patterns are generated by line integral convolution (LIC). This visualization is combined with animation based on motion along the vector field. This decoupling of the line direction from the direction of animation allows us to choose the spatial frequencies along the direction of motion independently from the length scales along the LIC line patterns. Vision research indicates that local motion detectors are tuned to certain spatial frequencies of textures, and the above decoupling enables us to generate spatial frequencies optimized for motion perception. Furthermore, we introduce a combined visualization that employs orthogonal LIC patterns together with conventional, tangential streamline LIC patterns in order to benefit from the advantages of these two visualization approaches; the combination of orthogonal and tangential LIC is achieved by two novel image-space compositing schemes. In addition, a filtering process is described to achieve a consistent and temporally coherent animation of orthogonal vector field visualization. Different filter kernels and filter methods are compared and discussed in terms of visualization quality and speed. We present respective visualization algorithms for 2D planar vector fields and tangential vector fields on curved surfaces, and demonstrate that those algorithms lend themselves to efficient and interactive GPU implementations.

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A PDF version can be found here.

Uniform vector field

These two videos show the difference between the standard LIC approach and the orthogonal vector field visualization. The left video displays animated streamlines of standard LIC. Note that it is hard to perceive the motion of the flow in this first video. The second video shows exactly the same vector field with the same animation speed, but based on orthogonal visualization.

Shear flow

These videos show a shear flow. This kind of vector field is difficult to visualize with the orthogonal vector field approach, since it is impossible to maintain perpendicular LIC lines everywhere in the flow field. However, we can handle these shearing flows e.g. by filtering them with an exponential filter kernel (further explanation in Section IV.C of the paper). The three different videos show the impact of the alpha blending value. For the first video, the alpha value is set to 1, which means that no blending is performed at all. The second video shows an alpha value of 0.1 and the third video is filmed with an alpha value of 0.03. Other parameters remain unchanged for each of the three videos.
The forth video shows a different way of overcoming the problem with shearing flow. Here, orthogonal LIC lines are shortened in regions of shear flow. This approach allows to forego the third stage of temporal filtering.


In these five videos, the effect of increasing filter length is demonstrated. An increased filter length leads to improved temporal coherence in the area of shearing flow (discussion of this topic in Section IV.C of the paper).

2D convection

Standard LIC and orthogonal LIC are compared for convection flow in 2D. The first video uses standard LIC, whereas the second video uses our approach of orthogonal vector field visualization. In both videos, the same CFD vector field is displayed. The corresponding screenshots are shown in the color plate of the paper as well (see Figures 7a and 7b).

Three dimensional flow

Again a comparison of standard LIC and orthogonal LIC, this time for surfaces in 3D. We used the same artificial 3D vector field for both videos. The flow is tangential to the surface of the torus at all times. The first video visualizes the flow using standard LIC, whereas the second video uses our approach of orthogonal vector field visualization. Note that it is much harder to perceive the vector flow in the first video compared to the second one.

Automotive CFD simulation

These videos show the animated flow visualization of a CFD simulation data set from the automotive industry. In both videos, orthogonal vector field visualization is used. Screenshots of that scene are shown in the color plate of the paper as well (see Figures 10a and 10b). Car geometry and vector field were kindly provided by the BMW Group.

Combined LIC

In these two videos the new combined LIC approach is shown. The left video shows interweaved LIC for the 2D case. The second video on the right shows an example of engraved LIC for the 2.5D case.

These two videos show variations of the combined LIC approach. On the left side, the orthogonal LIC lines are four times shorter than the conventional LIC lines. The second video on the right side shows short conventional LIC lines and orthogonal LIC lines that are four times longer.