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.
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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.
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.
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
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).
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.
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.