The VECTOR_FIELD procedure is used to place colored, oriented vectors of specified length at each vertex in an input vertex array. The output can be sent directly to an IDLgrPolyline object. The generated display is generally referred to as a hedgehog display and is used to convey various aspects of a vector field.

## Syntax

VECTOR_FIELD, *Field*, *Outverts*, *Outconn* [, ANISOTROPY=*array*] [, SCALE=*value*] [, VERTICES=*array*]

## Arguments

### Field

Input vector field array. This can be a [3, *x*, *y*, *z*] array or a [2, *x*, *y*] array. The leading dimension is the vector quantity to be displayed.

### Outverts

Output vertex array ([3, *N*] or [2, *N*] array of floats). Useful if the routine is to be used with Direct Graphics or the user wants to manipulate the data directly. If you are creating an IDLgrPolyline object, this output argument can be used as the input to the IDLgrPolyline::Init X argument.

### Outconn

Output polyline connectivity array to be applied to the output vertices. If you are creating an IDLgrPolyline object, this output argument can be used as the input to the IDLgrPolyline::Init /POLYLINES keyword.

## Keywords

### ANISOTROPY

Set this keyword to a two- or three-element array describing the distance between grid points in each dimension. The default value is [1.0, 1.0, 1.0] for three-dimensional data and [1.0, 1.0] for two-dimensional data.

### SCALE

Set this keyword to a scalar scaling factor. All vector lengths are multiplied by this value. The default is 1.0.

### VERTICES

Set this keyword to a [3, *n*] or [2, *n*] array of points. If this keyword is set, the vector field is interpolated at these points. The resulting interpolated vectors are displayed as line segments at these locations. If the keyword is not set, each spatial sample point in the input Field grid is used as the base point for a line segment.

## Version History

5.3 |
Introduced |