2004

848 | Glossary
block definition table The nongraphical data area of a drawing file that stores block
definitions. See also named object.
block instance See block reference.
block reference A compound object that is inserted in a drawing and displays the
data stored in a block definition. Also called instance. See also block and block defini-
tion. (INSERT)
B-spline curve A blended piecewise polynomial curve passing near a given set of
control points. See also Bezier curve. (SPLINE)
bump map A map in which brightness values are translated into apparent changes
in the height of the surface of an object.
button menu The menu for a pointing device with multiple buttons. Each button
on the pointing device (except the pick button) can be defined in the AutoCAD menu
file acad.mnu in the BUTTONSn
and AUXn sections.
BYBLOCK A special object property used to specify that the object inherits the color
or linetype of any block containing it. See also BYLAYER.
BYLAYER A special object property used to specify that the object inherits the color
or linetype associated with its layer. See also BYBLOCK.
circular external reference An externally referenced drawing (xref) that references
itself directly or indirectly. AutoCAD ignores the xref that creates the circular
condition.
clipping planes The boundaries that define or clip the field of view. (DVIEW)
CMYK For cyan, magenta, yellow, and key color. A system of defining colors by specify-
ing the percentages of cyan, magenta, yellow, and the key color, which is typically
black.
color map A table defining the intensity of red, green, and blue (RGB) for each
displayed color.
command line A text area reserved for keyboard input, prompts, and messages.
construction plane A plane on which planar geometry is constructed. The XY plane
of the current UCS represents the construction plane. See also elevation and user coor-
dinate system (UCS).
continued dimension A type of linear dimension that uses the second extension
line origin of a selected dimension as its first extension line origin, breaking one long
dimension into shorter segments that add up to the total measurement. Also called
chain dimension. (DIMCONTINUE)
control frame A series of point locations used as a mechanism to control the shape
of a B-spline. These points are connected by a series of line segments for visual clarity
and to distinguish the control frame from fit points. The SPLFRAME system variable
must be turned on to display control frames.
control point See control frame.
coordinate filters Functions that extract individual X, Y, and Z coordinate values
from different points to create a new, composite point. Also called X,Y,Z point filters.