The Automatic AEC Dimensioning System first appeared in Autodesk Architectural Desktop 3 and was originally designed for the European version of the program. Now these dimensioning routines have become a hit with ADT users everywhere.

In this tutorial you'll learn how to use this system, which should improve your efficiency and your productivity. And if you're more comfortable dimensioning objects with standard AutoCAD dimensions, you still have those options.

How It Works
Automatic dimensioning is a variant of standard AutoCAD dimensioning and to use this tool effectively, you should have a good understanding of the standard system first.

You can only use automatic AEC dimensions to dimension such AEC objects as walls, windows, stairs, and structural members.

When you create automatic AEC dimensions, you pick AEC objects, and dimension logical points on them. There are a number of logical points—for example, center of openings, width of walls, dimensioning to outside boundary of windows, and so on—to choose from for every object. Before adding a dimension, you must decide which of those points are relevant for your purposes.

Once you've selected these logical points, you can apply styles to them. These logical dimension points are associated with the AEC building objects. If you move, add to, delete, or otherwise change the dimensioned object, the dimension points are automatically updated.

Setting Up Automatic Dimensioning
To access the Dimensioning System, for your drawings, you must select it during program installation. At some point during the software setup procedure, the screen shown in Figure 1 appears. Just select the Install radio button on the International Extensions pane to turn on automatic dimensioning and then proceed with the installation. If you have already installed Architectural Desktop without this option, just call for uninstall which will allow you to add or change features.

Figure 1: Select the Install radio button under International Extensions when installing ADT.
(click image to enlarge)

Accessing the AEC Dimension Toolbar
To access the AEC Dimension toolbar:

1. Select View >Toolbars > from the main Architectural Desktop menu, which opens the Customize dialog box.

2. In this dialog box, select the Toolbars tab.

3. Select AECARCHX in the menu group and then select the AEC Dimension check box. The AEC Dimension toolbar displays (see Figure 2).

Figure 2: The AEC Dimension toolbar.

Chaining AEC Objects
In Architectural Desktop, chains (levels) hold dimension data for the AEC object. So, for example, Figure 3 has two chains.

Figure 3: Chains of dimension data.

Autodesk Architectural Desktop can have up to 10 chains.

Setting Automatic AEC Dimension Styles
1. Start a new Autodesk Architectural Desktop 3.3 drawing using the Aec arch [imperial] template, and select the Model layout.

2. Select Format > Text Style from the main toolbar menu and create a new style named StylusBT using the TT Stylus BT font.

3. Select the AEC Dimension Styles icon on the AEC Dimension toolbar (see Figure 4), which opens the Style Manager dialog box (see Figure 5).

Figure 4: Select the AEC Dimension Styles icon.

4. In the Style Manager dialog box, double-click the Standard (2 chains) style to bring up the AEC Dimension Style Properties dialog box.

Figure 5: Double-click the Standard (2 chains) style.

5. In the AEC Dimension Style Properties dialog box select the Display Props tab.

6. Click the Edit Display Props button to open the Entity Properties dialog box (see Figure 6).

During software development, an override was added to the Standard (2 chains) AEC Dimension Styles. If you open it, you will see that the overide has been applied.

7. In the Entity Properties dialog box, select the Contents tab (see Figure 6).

You will set the automatic dimensioning characteristics from this tab.

Figure 6: In the Entity Properties dialog box select the Contents tab.
(click image to enlarge)

9. Select Opening/Door/Window from the Apply to list box, and select the Center check box.

10. Select the Chain2 check box, select Wall from the Apply to list box, and select the Outer Boundaries Complete check box on the Wall pane.

11. Reselect Opening/Door/Window under Apply to, and clear all check boxes.

12. Select the Other tab and then from the Dimension Style drop-down list box, choose AEC Dimension [Small] (see Figure 7).

Figure 7: Select the Other tab and set the Dimension Style to AEC Dimension [Small].

13. Click the Edit button to open the Dimension Style Manager dialog box (see Figure 8), which is the default style manager for AutoCAD dimensions.

Figure 8: The default AutoCAD Dimension Style Manager.
(click image to enlarge)

14. In this dialog box, click the Modify button to open the Modify Dimension Style dialog box (see Figure 9).

15. In this dialog box select the Lines and Arrows tab.

16. Make Extend beyond ticks (under Dimension Lines) 1/8" and Baseline spacing 1/8".

17. Make Extend beyond dim lines 1/8" (under Extension Lines), Offset from origin 1/16", and then select the Text tab.

18. On this tab, make the settings shown in Figure 9 and then select the Fit tab.

Figure 9: On the Text tab, make the settings shown in this figure.
(click image to enlarge)

19. On the Fit tab set the Use overall scale of option to 48 (under Scale for Dimension Features), and select the Primary Units tab.

20. On this tab set the Unit format to Architectural and Precision to 1/32".

21. Close all the dialog boxes by clicking OK until you return to the Entity Properties dialog box.

22. In this dialog box set the distance between Chains to 2'-0". (This distance is relative to real-world distance since you are dimensioning in Model Space, which is in real-world units.)

23. Make sure the Use Fixed Length Extension Line check box is cleared, and then click the OK button.

24. Close all the dialog boxes.

Now you are ready to test the automatic AEC Dimension Styles.

25. In the Model layout, insert a 20'-long-by-12"-wide Standard wall. Add another wall perpendicular to this wall, and insert three 3'-0"-wide windows (see Figure 10).

Figure 10: Insert a 20'-long-by-12"-wide Standard wall.

26. Select the AEC Dimension Styles icon on the AEC Dimension toolbar; select the walls and windows you created with a selection marquee, and then press the Enter key.

27. Pick a point above the wall where you want the first chain to appear, and then pick a second point below the first point in the direction of 270 degrees. Turn on POLAR to make this easier (see Figure 11).

Figure 11: Pick a point above the wall where you want the first chain to appear, and then pick a second point below.

Your dimensions should appear as shown in Figure 12.

Figure 12: The final dimensioned wall.

28. Move, Modify, and delete objects. Notice that the AEC Dimensions will automatically update. (Figure 13)

Figure 13: When you move, modify, or delete AEC objects, dimensions are automatically updated y update the dimensions.

Conclusion
This tutorial reveals just a small example of the power of the Autodesk Architectural Desktop 3.3 AEC Dimensioning System. If you wish, you can manually adjust this system, or if you prefer you can work in standard AutoCAD dimensions. Although the system only works with certain AEC objects now, its speed and efficiency will surely increase your productivity.

Good Luck, Ed Goldberg AIA