Visualizing Vector Volume Data :: Volume Visualization Techniques (3-D Visualization)

3-D Visualization

Visualizing Vector Volume Data

Vector volume data contains more information than scalar data because each coordinate point in the data set has three values associated with it. These values define a vector that represents both a magnitude and a direction. The velocity of fluid flow is an example of vector data.

MATLAB supports a number of techniques that are useful for visualizing vector data:

Stream lines trace the path that a massless particle immersed in the vector field would follow.
Stream particles are markers that trace stream lines and are useful for creating stream line animations.
Stream ribbons are similar to stream lines, except that the width of the ribbons enables them to indicate twist. Stream ribbons are useful to indicate curl angular velocity.
Stream tubes are similar to stream lines, but you can also control the width of the tube. Stream tubes are useful for displaying the divergence of a vector field.
Cone plots represent the magnitude and direction of the data at each point by displaying a conical arrowhead or an arrow.

It is typically the case that these functions best elucidate the data when used in conjunction with other visualization techniques, such as contours, slice planes, and isosurfaces. The examples in this section illustrate some of these techniques.

Using Scalar Techniques with Vector Data

Visualization techniques such as contour slices, slice planes, and isosurfaces require scalar volume data. You can use these techniques with vector data by taking the magnitude of the vectors. For example, the wind data set returns three coordinate arrays and three vector component arrays, u, v, w. In this case, the magnitude of the velocity vectors equals the wind speed at each corresponding coordinate point in the volume.

```
wind_speed = sqrt(u.^2 + v.^2 + w.^2);
```

The array wind_speed contains scalar values for the volume data. The usefulness of the information produced by this approach, however, depends on what physical phenomenon is represented by the magnitude of your vector data.

Defining Isocaps Specifying Starting Points for Stream Plots