8

Aliasing/Antialiasing 1001
there are periods with no feet on the ground,
causing the biped to become airborne, or ballistic.
For example, running, hopping, and jumping are
ballistic gaits with airborne periods.
Aliasing/A ntia liasing
Pyramidisaliasedonleft,antialiasedonright.
Aliasingisthestaircaseeffectattheedgeofaline
or area of color when it’s displayed by an array of
discrete pixels.
Antialiasing smoothes the st a ircase effect that
occurs when diagonal or curved lines or borders
are drawn on raster displays consisting of square
or rectangular pixels. Antialiasing can be either on
or off. Turn this off only when you’re rendering
test images and want greater speed. Leave it on at
all other times.
You can also turn antialiasing off for the Material
Editor sample slots to speed up redraw of the
sample objects. Click the Options button in the
Material Editor and turn on the Antialias toggle on
the Material Editor Options dialog. Defau lt=off.
Note: To control whether or not a background
image is affected by the renderer’s antialiasing
filter, choose Customize > Preferences >
Rendering and then turn on Filter Background in
the Background group. Default=off.
Alpha Channel
Alpha channel shown in black, on the right
Alpha is a type of data, found in 32-bit bitmap
files, that assig ns transparency to the pixels in the
image.
A 24-bit truecolor file contains three channels of
colorinformation:red,green,andblue,or
RGB
(page 3–1095)
. Each channel has a particular
intensity or value at each pixel. The intensity of
each channel determines the color of the pixel in
the image.
Byaddingafourth,alphachannel,thefilecan
specify the transparency, or opacity, of each of the
pixels. An alpha value of 0 is tr ansparent, an alpha
value of 255 is opaque, and values in between are
semi-transparent. Transparency is important for
compositing (page 3–1016) operations, such as
those in Video Post, where several images are
blended together in layers.
An alpha channel is particularly useful for the
partly tr ansparent pixels around the
aliased (page
3–1001)
edge of an object in a rendered image.
These pixels are used for compositing. An image
suchastheoneshownabovecanbecomposited
smoothly on to a different background if an alpha
channel is produced and saved with the image.
Each channel of a truecolor bitmap file is defined
by 8 bits, pro viding 256 levels of intensity. Thus, an
RGB file is 24-bit with 256 levels each of red, green,
and blue. An RGBA file (red, green, blue, alpha)