Apple Motion 3 - Manual (Page 723)

Chapter 8 Working with Particles 723
Start Point (Line, Wave): Two sliders that define, in X and Y coordinates, the first point
of the line used as the emitter shape. Click the disclosure triangle to modify the Z
position of the start point. You can adjust these values in the Canvas using the
onscreen controls (with the Adjust Item tool).
End Point (Line, Wave): Two sliders that define, in X and Y coordinates, the second
point of the line used as the emitter shape. Click the disclosure triangle to modify the Z
position of the start point. You can adjust these values in the Canvas using the
onscreen controls (with the Adjust Item tool).
Shape Source (Geometry): An image well where you can specify an object that defines
the shape of the emitter. Spline objects may be dropped onto this well to assign the
desired shape.
Image Source (Image): An image well where you can specify the object used to define
the shape of the emitter. Any image or movie clip can be dropped onto this well to
assign the desired shape.
Emission Alpha Cutoff (Image): When the Image Source object contains an alpha
channel, this slider defines the minimum opacity value that is necessary to create
particles at that point on the source image. For example, when set to 25%, particles
appear only where the alpha value of the image is equal to or greater than 25%
opacity. The lower the Emission Alpha Cutoff value, the more particles appear. In order
for this parameter to be effective, the alpha channel needs to have areas of varying
transparency.
Emission Angle (all 2D shapes): Available for 2D emitter shapes, this dial sets the
direction in which particles travel. This parameter works in conjunction with the
Emission Range parameter. It is equivalent to one of the functions of the graphical
emission control in the Emitter HUD.
Note: When using an emitter shape other than a point, such as a line, circle, rectangle,
spiral, burst, or wave, and Outline is chosen from the Arrangement pop-up menu,
setting the Emission Angle parameter to 180 degrees and the Emission Range
parameter to 0 degrees restricts the emission of particles to the inside of the shape.
Setting the Emission Angle parameter to 0 degrees and the Emission Range parameter
to 0 degrees restricts the emission of the particles to outside of the shape.
Emission Range (all shapes): A dial that restricts the area around the center of each
emission point from which particles are generated, in the direction of the Emission
Angle. It is equivalent to one of the functions of the graphical emission control in the
Emitter HUD.
Note: When using a line, circle, rectangle, spiral, burst, or wave (but not geometry),
setting the Emission Range parameter to 0 degrees keeps particles perpendicular to
the emitter when they emerge.