Routines (alphabetical) > Routines: F > FLOW3

# FLOW3

The FLOW3 procedure draws lines representing a 3D flow/velocity field. Note that the 3D scaling system must be in place before calling FLOW3. This procedure works best with Z buffer output device.

This routine is written in the IDL language. Its source code can be found in the file `flow3.pro` in the `lib` subdirectory of the IDL distribution.

## Examples

; Create a set of random three-dimensional arrays to represent
; the field:
vx = RANDOMU(seed, 5, 5, 5)
vy = RANDOMU(seed, 5, 5, 5)
vz = RANDOMU(seed, 5, 5, 5)
; Set up the 3D scaling system:
SCALE3, xr=[0,4], yr=[0,4], zr = [0,4]
; Plot the vector field:
FLOW3, vx, vy, vz

## Syntax

FLOW3, Vx, Vy, Vz [, ARROWSIZE=value] [, /BLOB] [, LEN=value] [, NSTEPS=value] [, NVECS=value] [, SX, SY, SZ=vector]

## Arguments

### Vx, Vy, Vz

3D arrays containing X, Y, and Z components of the field.

## Keywords

### ARROWSIZE

Size of arrowheads (default = 0.05).

### BLOB

Set this keyword to draw a blob at the beginning of each flow line and suppress the arrows.

### LEN

Length of each step used to follow flow lines (default = 2.0). Expressed in units of largest field vector (i.e., the length of the longest step is set to len times the grid spacing.

### NSTEPS

Number of steps used to follow the flow lines (default = largest dimension of Vx / 5).

### NVECS

Number of random flow lines to draw (default = 200). Only used if Sx, Sy, Sz are not present.

### SX

### SY

### SZ

Optional vectors containing the starting coordinates of the flow lines. If any of SX, SY, and SZ are specified, all three vectors must be specified. If omitted random starting points are chosen.

## Version History

Pre 4.0 | Introduced

## See Also

VERT_T3D, VERT_T3D