Apple Motion 3 - Manual (Page 701)

Chapter 8 Working with Particles 701
2 In the HUD, click anywhere along the outer edge of the emission control and drag to
define a narrow segment that limits the range of the angle at which particles are
created (the emission range).
Both points defining the emission range rotate around the center of the emission
control symmetrically, so your initial wedge points to the right. As you adjust the
emission range, the particles rearrange themselves in the Canvas, enabling you to see
the resulting effect.
3 To make the particles drift upward, drag in the middle of the Emission Range segment,
rotating the arrow counterclockwise until it points up and slightly to the right of the
center control.
The emission angle of the particles updates in the Canvas to reflect the new setting in
the HUD.