Module: Stream Surface ()

Description:

This module computes stream surfaces of an arbitrary 3D vector field. A stream surface consists of multiple interconnected streamlines started along a predefined line source. The algorithm automatically inserts new streamlines in divergent regions of the field. Likewise, in convergent regions streamlines are automatically removed. The resulting stream surfaces can be accumulated in a separate Surface object. In this way further post-processing is facilitated, for example, computation of a LIC texture using Stream LIC Surface.

Connections:

Data [required]
The 3D vector field to be visualized.

Colormap [optional]
Optional colormap. By default, the current stream surface will be display in wireframe mode and will be colored according to the arc-length of the streamlines forming the stream surface. This port is hidden if the Data port is connected to an Unstructured Model Field. In that case, the colormap of the data set is used for the display.

Ports:

Colormap

Port to select a colormap. See Connections section.

Origin

This port defines the seed point of the stream surface. By pressing the menu button options a crosshair dragger can be activated which allows you to change the seed point interactively in 3D.

Actually, in order to compute a stream surface not only a seed point but a seed line is required. Starting from the seed point, such a line will be defined automatically taking into account the seed selection mode chosen in port Action.

Resolution

Controls the resolution of the discretized stream surface or, more precisely, the preferred edge length of the triangulation. Smaller values results in more details.

Length

Value n determines how far the surface should be traced in backward direction. Value m determines how far the surface should be traced in forward direction. Value width determines the extent of the seed line. The actual lengths in physical space depend on the value of port resolution. All values may be changed using the right mouse buttons by means of a virtual slider.

Action

This port provides push buttons allowing you to store the current stream surface in a surface object (add to result), respectively to remove all triangles from this surface again (clear result). Moreover, the port provides an option menu allowing you to select the mode used for automatic seed line definition. The following modes are supported:

Binormal: The seed line will be traced in a direction perpendicular to both the streamline's tangent and normal (curvature) direction. Often this gives quite meaningful results. However, note that in general the stream surface's normal vectors do not coincide with the streamline's curvature vectors except at the seed line.

Normal: The seed line will be traced along the field line's normal (curvature) direction.

X-axis: The seed line is chosen in x-direction

Y-axis: The seed line is chosen in y-direction.

Z-axis: The seed line is chosen in z-direction.

Commands:

setLineWidth <width>
Sets line width of wireframe model.

setTolerance <eps>
Sets relative tolerance used for field line integration. The default is 0.001 times the sampling width set in port resolution.

doLineSet {0|1}
If argument is 1 only streamlines will be displayed instead of the stream surface's triangulation.

setDrawStyle {1|2}
Allows you to set the draw style used in surface mode, i.e., when doLineSet is off. A value of 1 denotes wireframe mode, while a value of 2 denotes shaded surface mode. In order to display the surface in a more fancy way convert it into a surface object and use Surface View.