Apple Motion 4 - Manual (Page 617)

For particle systems containing multiple cells, the Emitter HUD parameters simultaneously
modify the effect of each cell’s parameters relative to one another. This means that for a
particle system consisting of two cells with different scale values, changing the scale in
the HUD resizes both cells simultaneously. For example, increasing the scale in the HUD
by 200% does not change the scale of both cells to 200%, but resizes the cells relative to
their original scale values.
Original particle system Particle system scaled to 200 percent
For this reason, in emitters with multiple cells, the HUD parameters are displayed as
percentages. When you modify the parameters of a single cell, the cell parameters are
adjusted directly.
Birth Rate: A slider that defines how many particles are created every second.
Life: A slider that defines how long each particle remains onscreen (in seconds) before
disappearing from existence.
Scale: A slider that defines the size of each particle, relative to the original size of the cell.
Emission Control: A graphical control that lets you modify several parameters.
• Emission Range (2D only): Drag the two points on the outer ring of the graphical emission
control to define the range of degrees at which particles are generated. In other words,
the Emission Range parameter defines the size of the “slice” of the pie graph that the
particles fill when generated.
• Emission Angle: Drag inside the emission control to change the direction in which
particles are emitted, inside the area defined by the Emission Range.
617 Chapter 11 Working with Particles