Modifying a Locus

You can change the color and line width of a locus just as you do with other objects, and you can show the label of a point locus. There also are some special modifications you can make which apply only to loci.

When a locus is first constructed, the number of samples it uses is determined by a value on the Sampling Preferences panel of Advanced Preferences.

Determining the Number of Samples

After a locus has been constructed, you can use the Plot Properties panel of Properties to change the number of samples. In general, the higher the number of samples, the better the quality of the locus, but the slower it is to drag.

Continuous and Discrete Point Loci

If the locus is a point locus, you can use the Plot Properties panel of Properties to determine whether the locus is displayed in continuous form (with the samples connected to each other) or in discrete form (with a separate dot for each sample).

A point locus is simply the locus of a point, as opposed to the locus of a circle or line or other object.

Resizing a Point Locus

If a point locus is based on a closed path (such as a circle) or a finite path (such as a segment or arc), the domain of the driver is fixed. But if the drive path is infinite and open (such as a ray or line), the domain of the driver—and therefore, the potential size of the locus—is infinite! If possible, Sketchpad limits the domain based on the portion of the path that is visible on the screen. Such a point locus (on an infinite open domain) displays an arrowhead on the end of the locus.

If you wish to change the displayed size of a point locus, use the Arrow tool to drag the arrowhead at either end of the locus. Drag in the direction that the arrowhead points to increase the size of the locus; drag in the opposite direction to decrease the size of the locus.