How to Turn Dimensional Constraints into Annotational Constraints in AutoCAD 2014 - dummies

How to Turn Dimensional Constraints into Annotational Constraints in AutoCAD 2014

By Bill Fane, David Byrnes

After all the hard work of adding dimensional constraints to a drawing in AutoCAD, it would be a downright shame to have to go back and apply regular dimensions, wouldn’t it? Well, you don’t have to. You can make dimensional constraints look and behave like regular dimensions. You can go the other way, too, and make your regular dimensions act like dimensional constraints.

Dimensional constraints are available in two flavors:

  • Dynamic: In this default form, a dynamic constraint is gray, with a padlock icon next to it in the drawing area. You can make the constraint appear and disappear by clicking Show All in the Dimensional panel. Dynamic constraints don’t plot, and they’re always legible because they resize as you zoom in and out of the drawing.

  • Annotational: This form is controlled as an object property, so you have to set it in the Properties palette. Though annotational constraints plot, they don’t resize as you zoom in and out, and they don’t disappear as you toggle the Show All button on and off. Annotational constraints conform to dimension style settings.

The dimension name format of annotational constraints can be set to Name, Value, or Name and Expression, just like dynamic constraints. If you want to plot a drawing with annotational constraints, reset the format so that it doesn’t show the dimension name or the expression.

Here’s how to turn dynamic dimensional constraints into annotational constraints:

  1. Open a drawing that contains some geometry with dimensional constraints.

    You can also start a new drawing, draw some simple geometry, and add a dimensional constraint or two.

  2. Select a dynamic constraint, right-click, and choose Properties.

    The Properties palette opens with the object properties of the selected dimensional constraint listed in table form.

  3. Click in the Constraint Form field, and in the drop-down list, change Dynamic to Annotational.

    The dynamic constraint becomes annotational and takes on the appearance of the current dimension style. If you change the dimension style in the Properties palette, the annotational constraint updates to the new dimension style format.


    You can go the other way, too — from regular dimension objects to dimensional constraints to convert an existing dumb drawing to an intelligent parametric one.

  4. Add a linear, radius, diameter, aligned, or angular dimension (that is, a regular dimension, not a dimensional parameter) to your drawing geometry.

    Nearly every type of dimension object has a parametric analog; the exceptions are arc length, jogged radius, jogged linear, and ordinate dimensions.

  5. Click Convert in the Dimensional panel, select a dimension type (refer to Step 4), and press Enter.

    The Dimensional Constraint text box displays as soon as you click an associative dimension, and the dimension becomes a dynamic constraint as soon as you press Enter.

The only clue that a dimension is an annotational constraint rather than a regular associative dimension is the padlock icon that appears next to the dimension value. You can turn off the display of the padlock from the Constraint Settings dialog box, but you should leave it on. It doesn’t plot anyway, and you might decide to delete the dimension without realizing that it’s controlling your object geometry.

Annotational dimensions can also be annotative so that they size themselves automatically to the drawing scale. Annotative and annotational dimensions are also associative, so you can have annotative annotational associative dimensions. (Try saying that quickly after a few drinks.)

You get the most mileage from this feature when you incorporate both geometric and dimensional constraints with other precision techniques. In fact, if you start a drawing by using Snap, Ortho, Osnap, and other precision techniques before you add dimensional and parametric constraints, you’ll be well on your way to creating a library of intelligent drawings that maintain your design intent.

Geometric and dimensional constraints can be equivalent. For example, a 90-degree-angle dimensional constraint is equal to a perpendicular geometric constraint, and AutoCAD doesn’t let you apply both.

Geometric constraints apply “to infinity,” so you can synchronize objects from one orthographic view with objects in another.

For example, coincident and collinear constraints can link objects in the front view with their equivalents in the top and right-side views, and liberal use of the equal constraint means that you should never have to measure or dimension anything twice, you should never need more than minimal construction geometry, any changes in one view reflect through to the others, and your views always remain orthogonally aligned.