Reference and Constraints with AutoCAD - Section 3

12.3 Restriction parameters

The dialog box in the “Geometrics” section of the “Parametric” tab allows us to establish which constraints we can display. You also have an option for Autocad to automatically infer and apply what constraints can be applied to an object as you draw.

In this same dialog box we activate or deactivate the restrictions that can be applied to an object automatically with the button of the same name of the ribbon.

12.4 Restriction by dimensions

As we defined before, the restrictions by dimensions allow to establish specific values ​​for distances, angles and radii of the objects. The advantage of this restriction is that it can be dynamic, that is, we can modify the value of the dimension and the object will modify its dimensions. Likewise, it is possible to express the value of constraints by dimension as a result of a function and even of an equation.
The restrictions by dimension are: Linear, aligned, radius, diameter and angular. Let's see some examples.

As you can see, each dimension receives a specific name, which can be called in an expression to establish a restriction by dimension defined by the values ​​of another object.

We can add custom variables to these expressions through the Parameter Manager, which will also help us to know the current value of an expression.

In conclusion, the parametric constraints allow you to apply all the design ideas that come to mind without worrying (or caring) if those ideas escape or not to the geometric or dimensional specifications that must have what you are designing, since will already be indicated in the drawing itself. If you experience a change that is not possible, the restrictions will let you know immediately.
Finally, as we noted above, we will return to the parametric constraints once we see object editing.