When you use a Wacom stylus and tablet to create paint strokes with the Paint Stroke tool, the Apply Pen Speed behavior controls the width, opacity, spacing, angle, or jitter of the paint stroke based on the speed of your stylus on the tablet. (A paint stroke created using a mouse or trackpad can also be affected by the Apply Pen Speed behavior.)
Note: In the Paint Stroke Tool HUD, you can select how the speed of the stylus affects the stroke before the stroke is created. Use the Pen Speed setting in the HUD in combination with a Pen Speed behavior to affect more than one parameter of the stroke (such as Opacity, Width, or Jitter) using the same pressure data. The Pen Speed parameter also appears in the Advanced pane of the Shape Inspector.
You can adjust the Apply Pen Speed behavior using the following controls in the Behaviors Inspector:
Apply To: A pop-up menu that sets how your paint stroke is affected by pen speed. There are five options:
Width: The faster you move the pen, the more narrow the stroke; the slower you move the pen, the wider the stroke.
Opacity: The faster you move the pen, the less opaque the stroke.
Spacing: The faster you move the pen, the greater the spacing between stroke dabs.
Angle: The faster you move the pen, the greater the angle of the stroke dabs.
Jitter: The faster you move the pen, the greater the amount of jitter on the stroke. Jitter randomizes the position of the paint dabs so they appear more like particles.
Min Speed: A slider that adjusts the minimum threshold of speed sensitivity. Speed values below the minimum value are remapped to 0. For Opacity and Width, those values do not appear. For Spacing, Angle, and Jitter, the values are not modified. If the Min Speed and Max Speed (described below) parameters are plotted on a graph, Min Speed represents the minimum value, or 0. The area of the graph between Min Speed and Max Speed is remapped to the output values.
Max Speed: A slider that adjusts the maximum threshold of speed sensitivity. Speed values above the maximum value are remapped to 1. For Opacity, Width, Spacing, Angle, and Jitter, those values will have the greatest effect. If the Min Speed and Max Speed parameters are plotted on a graph, Max Speed represents the maximum value, or 1. The area of the graph between Min Speed and Max Speed is remapped to the output values.
Scale: A slider that determines the magnitude of the effect. The Scale slider defines the output range for the dabs based on the mapped values between minimum (0) and maximum (1) speed, multiplied by the value defined in the slider (or adjacent value slider). This amount is then applied to the channel (width, opacity, and so on) by multiplying (for width, opacity, spacing, and jitter) or adding (for angle). This control is independent of the Scale parameter in the Stroke pane of the Shape Inspector.
Invert: A checkbox that, when selected, inverts the attributes of the stroke created by the behavior. For example, if pen speed is set to affect the width of the stroke, thin areas of the stroke become wide and wide areas become thin when the checkbox is selected.