## 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.

### 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 omitted random starting points are chosen.

### 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
```

### Version History

Introduced: Pre 4.0