Freud User Manual

CHAPTER 5 Vectors

Instantiating a vector object
Loading data
Vector values
Other attributes
Spacing and style attributes
Color
Vector example

Instantiating a vector object

A new vector object is instantiating by clicking on the Vector button in the overlays panel; a new vector button will appear in the instance bar of the base window. The window associated with the popup window will appear once you click on the newly created button (see Fig. 15).

Loading data

Note that there are two data fields that need to be determined. One field specifies the U component of the vectors, and the other specified the V component. Both fields must be on the same grid.

The data browser can be connected to the U or V component by choosing the appropriate item in the Data menu, or by pressing control-U or control-V. Once you have connected to the component you want, data is loaded in the same manner as for the contour object.

Vector values

Once you have loaded in two vector variables, you must set the minimum and maximum vector magnitudes to be associated with the smallest and largest drawn vectors. You can automatically set them by choosing Autoset Vector Values from the Edit menu, or pressing control-A, or you can set them yourself. If they are set automatically, the values are set to bracket the minimum and maximum magnitude of the vectors in the data sets as determined by the equation

A vector that has a magnitude equal to the maximum magnitude will be drawn with a shaft that is the size specified by the Max vector length slider. A vector will not be drawn if its magnitude is less than the value determined by the Smallest vector slider.

Note that if you want all of the vectors to be the same size (to just indicate direction), set the minimum magnitude to a very large negative number.

Other attributes

Spacing and style attributes

The appearance of other vector attributes are controlled by selecting Spacing/Styles from the Properties menu

.. You can adjust the following items:

U grid-this determines the spacing in grid units between neighboring vectors for the U coordinate; a value of 1 implies that a vector will be drawn at every U grid point, a value of 2 implies every other grid point will have a vector.
V grid-similar to U grid, except that the V coordinate spacing is determined.
Angle-this item specified the angle between the head of the arrow, and the shaft of the arrow representing a vector.
Head filled-determine whether or not to fill the head of the arrow.
Style-determine the line style of the arrow shaft.
Color-determine the color of the arrow

Color

There are two ways of specifying the color of the vector arrows. The arrows can either be one color, or they can be colored as a function of a scalar field.

The color of the vectors is changed by selecting Color from the Properties menu.

By default, the color source is static; the arrow color is determined by selecting a color from the Static color menu.

If you wish to set the color of the vectors as a function of a scalar field, click on the Scalar field button. Connect the data browser to the scalar field by selecting Connect browser to scalar color field from the Data menu. Once you have selected and accepted a dataset, click on Set range limits to set the color intervals for the scalar field. Colors are selected in a manner similar to contour areas.

Vector example

This example contains the same overlays as Fig. 14, but with an additional vector overlay showing the surface winds.

Freud User Manual - 02 FEB 96

[Next] [Previous] [Top]

Generated with CERN WebMaker