2012

adaptive degradation A method of controlling performance that turns off
features in a certain order when performance falls below a specified level.
adaptive sampling A method to accelerate the anti-aliasing process within
the bounds of the sample matrix size. See also anti-aliasing.
adjacent cell selection A selection of table cells that share at least one
boundary with another cell in the same selection.
affine calibration A tablet calibration method that provides an arbitrary linear
transformation in two-dimensional space. Affine calibration requires three
calibration points to allow a tablet transformation that combines translation,
independent X and Y scaling, rotation, and some skewing. Use affine calibration
if a drawing has been stretched differently in the horizontal or vertical
direction. (TABLET)
alias A shortcut for a command. For example, CP is an alias for COPY, and Z
is an alias for ZOOM. You define aliases in the acad.pgp file.
aliasing The effect of discrete picture elements, or pixels, aligned as a straight
or curved edge on a fixed grid appearing to be jagged or stepped. See also
anti-aliasing.
aligned dimension A dimension that measures the distance between two
points at any angle. The dimension line is parallel to the line connecting the
dimension's definition points. (DIMALIGNED)
alpha channel Alpha is a type of data, found in 32-bit bitmap files, that
assigns transparency to the pixels in the image.
A 24-bit truecolor file contains three channels of color information: red, green,
and blue, or RGB. Each channel of a truecolor bitmap file is defined by 8 bits,
providing 256 levels of intensity. The intensity of each channel determines
the color of the pixel in the image. Thus, an RGB file is 24-bit with 256 levels
each of red, green, and blue.
By adding a fourth, alpha channel, the file can specify the transparency, or
opacity, of each of the pixels. An alpha value of 0 is transparent, an alpha
value of 255 is opaque, and values in between are semi-transparent. An RGBA
file (red, green, blue, alpha) is 32-bit, with the extra 8 bits of alpha providing
256 levels of transparency.
To output a rendered image with alpha, save in an alpha-compatible format
such as PNG, TIFF, or Targa.
ambient color A color produced only by ambient light. Ambient color is the
color of an object where it is in shadow. This color is what the object reflects
when illuminated by ambient light rather than direct light.
2288 | Glossary