Module: Illuminated Streamlines Surface ()

Description:

This module visualizes a surface vector field using so-called illuminated streamlines (ISL). The streamlines are sparsely seeded on the surface such that the underlying surface is still visible. This enables one to compare several vector fields on the same surface by applying Stream LIC Slice for one vector field and the Illuminated Streamlines Surface module for the second vector field.

To compute the streamlines, the algorithm uses the orthogonal vector field. Because the primal and its orthogonal vector fields are used, the method is called dual streamline seeding. The method was developed at ZIB and is published in the following article:

O. Rosanwo, C. Petz, S. Prohaska, I. Hotz and H.-C. Hege, Dual Streamline Seeding, Proceedings of the IEEE Pacific Visualization Symposium, 2009, pp. 9-16.

To prevent z-fighting artifacts when rendering the surface stream lines on a surface, one needs to enable polygon offset for the respective Surface View via the following command: Surface View setPolygonOffsetMode on.

Press the Apply button to start the computation. If no stream lines have been computed yet, nothing will be seen. Note that this button needs to be pressed whenever the streamline parameters have changed. For changing color, lighting etc. this is not required.

Connections:

Surface [required]
Surface on which the streamlines are to be computed and visualized.

VectorField [required]
Surface vector field or 3D vector field to be visualized.

Ports:

Color

This port determines the diffuse color of the streamlines.

View options

Lighting: Controls illumination of lines. If off, constant colored lines are drawn (flat shading).
Animate: Activates particle-like animation. The animation speed may be controlled via the command setAnimationSpeed.

Fade factor

Values smaller than 1 have the effect that line segments become more and more transparent in backward direction.

Transparency

Base transparency of the line segments.

Advanced

Options

If the first option is selected, the separatrices of the surface vector field will be explicitly added to the streamlines. Note that without this option the separatrices will only be used to improve the streamline seeding, and hence, the separatrices are not included in the set of streamlines. By selecting the second option, the streamlines will be pruned when they get too close to each other.

Separation distance

This parameter determines the closeness of the streamlines.

Line width

This port determines the resolution of the underlying triangular grid and thereby the smoothness of the lines.

Seed

Seed value for the random number generator that distributes the seedpoints. Seed value of 0 triggers a different distribution each time.