Autodesk AUTOCAD 2010 - PREVIEW GUIDE Manual page 15

AUTOCAD 2010 PREVIEW GUIDE
formulas to set the values of other constraints. For example, if you have a rectangle with constraints named
"length" and "width," you could define the value of "width" as "length/3" to constrain the rectangle's width to 1/3
of its length.
User-Defined Parameters
The Parameters Manager, available from the ribbon, enables you to manage dimensional parameters as well
as create and manage user-defined parameters. You can provide a meaningful name for the parameter and
then assign a numeric value or formula as its expression. A parameter's expression can reference other
parameters so that its value automatically updates when the other parameter values change.
Figure 24. Parameters Manager
Constraint Forms
Dimensional constraints can take one of two forms: Annotational or Dynamic. Both forms control geometry in
the same way, but they differ in their appearance and they way they are managed.
Dynamic dimensional constraints are not intended to be used as plotted annotation and they have a predefined
style that cannot be modified. The display height is controlled by the BPARAMETERSIZE system variable. The
visibility of dynamic constraints can be controlled in a variety of ways. First, you can show or hide all dynamic
constraints with two icons on the ribbon. Second, even if dynamic constraints are hidden, you can choose to
display them when a constrained object is selected, by using the checkbox in the Constraint Settings dialog or
the DYNCONSTRAINTMODE system variable. Finally, even if dynamic constraints are set to "Show All," they
will only appear if at least one of the constrained objects is visible (on a layer which is On and Thawed).
Annotational constraints look just like dimension objects, and are managed the same way. They have all the
same properties as regular dimensions, including Style. Annotational constraints are intended to be used for
plotted dimensional constraints.
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