Note: Please see the STREAMLINE function, which provides enhanced functionality and offers an interactive interface.
The STREAMLINE procedure generates the visualization graphics from a path. The output is a polygonal ribbon which is tangent to a vector field along its length. The ribbon is generated by placing a line at each vertex in the direction specified by each normal value multiplied by the anisotropy factor. The input normal array is not normalized before use, making it possible to vary the ribbon width as well.
Examples
The program show_stream.pro, located in the examples/doc/objects subdirectory of the IDL distribution, demonstrates the use of the STREAMLINE routine. To generate and display streamline ribbons with a sample dataset:
SHOW_STREAM
To display the same sample dataset using tubes rather than ribbons:
SHOW_STREAM, /TUBES
To view the IDL code used to create this display, enter
.EDIT SHOW_STREAM
at the command line in the IDL workbench.
Syntax
STREAMLINE, Verts, Conn, Normals, Outverts, Outconn [, ANISOTROPY=array] [, SIZE=vector] [, PROFILE=array]
Arguments
Verts
Input array of path vertices ([3, n] array).
Conn
Input path connectivity array in IDLgrPolyline POLYLINES keyword format. There is one set of line segments in this array for each streamline.
Normals
Normal estimate at each input vertex ([3, n] array).
Outverts
Output vertices ([3xn] float array). Useful if the routine is to be used with Direct Graphics or the user wants to manipulate the data directly.
Outconn
Output polygonal connectivity array to match the output vertices.
Keywords
ANISOTROPY
Set this input keyword to a three-element array describing the distance between grid points in each dimension. The default value is [1.0, 1.0, 1.0]
SIZE
Set this keyword to a vector of values (one for each path point). These values are used to specify the width of the ribbon or the size of profile at each point along its path. This keyword is generally used to convey additional data parameters along the streamline.
PROFILE
Set this keyword to an array of two-dimensional points which are treated as the cross section of the ribbon instead of a line segment. If the first and last points in the array are the same, a closed profile is generated. The profile is placed at each path vertex in the plane perpendicular to the line connecting each path vertex with the vertex normal defining the up direction. This allows for the generation of streamtubes and other geometries.
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