2011

underconstrained geometry Objects with unsolved degrees of freedom are
underconstrained.
underlay A DWF, or DGN file used to provide visual context in a drawing
file. Underlays cannot be edited, and do not provide the full range of
notification. Underlays cannot be bound to a drawing. See also external
reference (xref).
up direction A vector defining what direction is Up. By default this is the
positive Z – axis (0,0,+1).
The up direction and the north direction are always constrained such that
they are perpendicular to each other.
user coordinate system (UCS) A user-defined coordinate system that defines
the orientation of the X, Y, and Z axes in 3D space. The UCS determines the
default placement of geometry in a drawing. See also world coordinate system
(WCS).
user parameter Named user-defined variable (real number or an expression)
that can be used in expressions for dimensional constraints or other user
parameters.
UVW The material’s coordinate space. Used instead of XYZ because that is
usually reserved for the world coordinate system (WCS). Most material maps
are a 2D plane assigned to a 3D surface. The U, V, and W coordinates parallel
the relative directions of X, Y, and Z coordinates. If you look at a 2D map
image, U is the equivalent of X, and represents the horizontal direction of the
map. V is the equivalent of Y, and represents the vertical direction of the map.
W is the equivalent of Z and represents a direction perpendicular to the UV
plane of the map.
vector A mathematical object with precise direction and length but without
specific location.
vertex A location where edges or polyline segments meet.
vertical ribbon
The ribbon when it is oriented vertically, usually on the left or right of the
file window.
1410 | Glossary