Apple Motion 2 - Manual (Page 269)

Chapter 3 Basic Compositing 269
The Premultiplied Mix blend mode performs an unpremultiply composite—the
foreground image is assumed to be premultiplied. Artifacts may appear as a result of
unpremultiplying pixels whose RGB and alpha values are very small (resulting in pixels
with values of 255). In some cases, the hardware performs bilinear filtering and then
the blend mode unpremultiplies the alpha.
Drop Shadows
A drop shadow, by default, is a dark, translucent, offset shape that falls behind an
object, as if a light was shining on the object. Drop shadows are the same size as the
object to which they’re applied, although blurring a drop shadow may enlarge it
somewhat.
They create the illusion of depth, with the result that the foreground object seems to
pop out at the viewer. For this reason, drop shadows are frequently used to create the
impression of space between two overlapping layers.
01112.book Page 269 Sunday, March 13, 2005 10:36 PM