How to Create and Use Dynamic Area Fields in AutoCAD

Fields are dynamically linked properties in AutoCAD that update automatically when the associated object properties change. A common example of a field is the current date. When you add a date field to an AutoCAD drawing, it always displays the current date without requiring manual text editing.

Similarly, many other fields can be utilized to make your drawings smarter. Most of these fields are widely implemented in blocks containing attributes, title block texts, and sheet sets. In the AutoCAD Sheet Set Manager, fields are extensively used to create label blocks, callout blocks, and automated title blocks.

This article explores a specific and practical use case of fields in AutoCAD: displaying an area dynamically within a floor plan.

Setting Up the Area Field

Suppose you want to display the area of a room in a floor plan so that the value updates automatically whenever the room boundaries are modified. To achieve this, you can insert an area field.

In this example, the door layer has been deactivated temporarily to establish a clean, continuous room boundary. The door can be reactivated after the field has been placed.

To add the area field to the room, start by configuring your text style, as fields inherit the properties of the active text style.

1. Type ST on the command line and press Enter to launch the Text Style window.
2. In the Text Style dialog box, select the “Simplex” font (or any other font required by your drafting standards).
3. Set the text height to 6″ for proper visibility on the drawing, click Apply, and then close the window.

The next step involves creating a closed boundary around the room perimeter using the BOUNDARY command.

1. Type BOUNDARY on the command line and press Enter.

2. Select “Polyline” from the object type dropdown menu within the Boundary Creation dialog box.

3. Click the “Pick Points” button.

4. Click anywhere inside the empty area of the room and press Enter to generate the closed polyline boundary.

With the boundary established, you can now insert the dynamic field.

1. Type FIELD on the command line and press Enter.

2. Select “Objects” from the Field Category dropdown menu, and then select “Object” from the Field Names list.

3. Click the “Select Object” icon next to the Object Type field, and select the polyline boundary created previously. The Field window will refresh to display specific object properties.

4. Select “Area” from the Property panel and choose your preferred architectural format from the Format list.

5. Click OK, then click inside the room to position the dynamic text field.

After unhiding the door layer, the final room layout containing the dynamic area field will display as shown below.

Customizing Field Display Settings

By default, fields display with a light grey background in the drawing workspace. This background acts as a visual guide to distinguish fields from standard multiline text (Mtext), but it does not appear when the drawing is plotted or printed.

If you prefer a clean workspace without the grey background, you can disable it through the Options menu.

1. Type OP on the command line and press Enter to open the Options window.
2. Navigate to the User Preferences tab.
3. Locate the Fields section and uncheck the “Display background for fields” checkbox.
4. Click OK to apply the changes.

Alternatively, you can control this visibility using the FIELDDISPLAY system variable. Setting FIELDDISPLAY to 1 keeps the background visible, while setting it to 0 removes it completely.

Managing Field Updates and System Variables

When you modify the geometry of the polyline boundary associated with your field, the underlying data updates automatically. However, these changes might not reflect immediately in your workspace view.

To force the text to display the updated information, regenerate the drawing workspace by typing RE and pressing Enter. You can also execute the UPDATEFIELD command to manually select and update specific fields across your drawing.

To automate how frequently fields evaluate and refresh, configure the FIELDEVAL system variable. You can specify a custom bitcode value by summing any combination of the following update triggers:

• 0: Disables all automatic updates; fields must be refreshed manually.
• 1: Updates fields automatically when the drawing file is opened.
• 2: Updates fields automatically when the drawing file is saved.
• 4: Updates fields automatically when plotting or printing the drawing.
• 8: Updates fields automatically when utilizing the eTransmit command.
• 16: Updates fields automatically whenever the drawing is regenerated using REGEN.