Apple Motion 4 - Manual (Page 635)

Size: This parameter is available when Rectangle or Box is chosen in the Shape pop-up
menu. Defines the size of the rectangle or cube from which particles are emitted. This
parameter is available whether the Arrangement is set to Outline, Tile Fill, or Random Fill.
When Rectangle is the selected shape, the Width and Height parameters are available.
When Box is selected, an additional Depth parameter is available.
Note: The Height is measured in project pixels; however, the Width is measured in square
pixels. This is done so that a shape that is numerically square will look square when Correct
for Aspect Ratio is turned on (checkmarked) in the View pop-up menu in the top-right
corner of the Canvas.
Columns: This parameter is available when one of the following is chosen in the Shape
pop-up menu: Rectangle, Circle, Image, Box, or Sphere; in addition, Arrangement must
be set to Tile Fill. This parameter specifies the number of horizontal emitter points on a
grid over the selected emitter shape. In the case of an irregular shape (nonrectangular),
grid points that fall outside of the shape are ignored.
Rows: This parameter is available when one of the following is chosen in the Shape
pop-up menu: Rectangle, Circle, Image, Box, or Sphere; in addition, Arrangement must
be set to Tile Fill. This parameter specifies the number of vertical emitter points on a grid
over the selected emitter shape. In the case of an irregular shape (nonrectangular), grid
points that fall outside of the shape are ignored.
Ranks: This parameter is available when Box or Sphere is chosen in the Shape pop-up
menu and Tile Fill is the selected Arrangement. This parameter specifies the number of
points in Z space on a grid over the selected shape from which particles are emitted.
Tile Offset: This parameter is available when one of the following is chosen in the Shape
pop-up menu: Rectangle, Circle, Image, Box, or Sphere; in addition, Arrangement must
be set to Tile Fill. Values from 0 to 100% offset the rows toward the right, and values from
0 to –100% offset the rows toward the left. A value of 50 or –50% creates a “brickwork”
pattern.
Image Source: This parameter is available when Image is chosen in the Shape pop-up
menu, and lets you 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.
Shape Source: This parameter is available when Shape is set to Geometry. This image
well allows you to specify an object that defines the shape of the emitter. Spline objects
may be dropped onto this well to assign the desired shape.
Emission Alpha Cutoff: This parameter is available when Image is chosen in the Shape
pop-up menu. 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.
635 Chapter 11 Working with Particles