left-to-right direction — if you move the cursor above or below the line. It draws a
AutoCAD prompts you:
Specify dimension line location or
[Mtext/Text/Angle/Horizontal/Vertical/Rotated]:
7. Move the mouse to generate the type of dimension you want, horizontal or vertical, and then click wherever you want to place the dimension line.
When you’re specifying the dimension line location, you usually
AutoCAD draws the dimension.
If you want to be able to align subsequent dimension lines easily, turn on Snap and set a suitable snap spacing — more easily done than said! — before you pick the point that determines the location of the dimension line. See Chapter 4 for more information about snap.
8. Repeat Steps 4 through 7 to create another linear dimension of the opposite orientation (vertical or horizontal).
9. Choose Dimension>Aligned or click the Aligned Dimension button on the Dimension toolbar.
The prompt includes an option to select an object instead of picking two points (you can use this technique with the Linear Dimension command, too):
Specify first extension line origin or <select object>:
10. Press Enter to choose the select object option.
AutoCAD prompts you:
Select object to dimension:
11. Select the line or other object that you want to dimension.
AutoCAD automatically finds the endpoints of the line and uses them as the extension line origin points, as shown in Figure 10-9.
Figure 10-9: Drawing a linear dimension by selecting an object.
AutoCAD prompts you:
Specify dimension line location or
[Mtext/Text/Angle]:
12. Click wherever you want to place the dimension line.
AutoCAD draws the dimension.
After you have the hang of ordinary linear dimensions, you should be able to master other common dimension types quickly. Draw some lines, arcs, and circles, and try the other dimension commands on the Dimension toolbar or menu.
Although AutoCAD includes special commands for dimensioning the diameter or radius of a circle or arc, you can use the linear dimension techniques described in the previous section to dimension these objects.
To draw a series of side-by-side dimensions whose dimension lines are perfectly aligned, use the DimCOntinue command. To draw an overall dimension above one or more smaller dimensions, use DimBAseline. If you use these commands often in your work, you may find that the QDIM (Quick DIMension) command provides a quick way to draw lots of dimensions in one fell swoop.
Figure 10-10 shows some results of using the more common additional dimensioning commands.
Figure 10-10: Examples of additional dimensioning commands.
Trans-spatial dimensioning may sound like the latest New Age fad — after all, most of Autodesk’s programmers do work in California — but actually it’s just a relatively new (circa AutoCAD 2002) dimensioning feature. There’s an age-old argument about whether to draw dimensions in model space, where the geometry that you’re dimensioning usually resides, or paper space. (See Chapter 3 for information about model space and paper space.) Most people have settled on dimensioning in model space, but sometimes dimensioning in paper space offers advantages — for example, when you want to dimension different parts of the same geometry in different paper space viewports.
Since AutoCAD 2002, the program works much better for dimensioning in paper space layouts — when you set the DIMSCALE system variable to 1.0 and then draw dimensions in paper space, AutoCAD can associate them with objects in model space.
Get comfortable with dimensioning in model space first. If you later want to try dimensioning in paper space, look up “dimensioning, methods” in the AutoCAD online help system.
Editing Dimensions
After you draw dimensions, you can edit the position of the various parts of each dimension and change the contents of the dimension text. AutoCAD groups all the parts of a dimension into a single object.
The easiest way to change the location of dimension parts is to use grip editing, which I describe in Chapter 6. Just click a dimension, click one of its grips, and maneuver away. You’ll discover that certain grips control certain directions of movement. Experiment a few minutes to see how they work.
If you want to change the look of a dimension part (for example, substitute a different arrowhead or suppress an extension line), use the Properties palette. (See Chapter 6 for more on the Properties palette.) All the dimension settings in the New/Modify Dimension Style dialog box (see “Adjusting style settings,” earlier in this chapter) are available in the Properties palette when you select one or more dimensions.
If you select one or more dimensions and right-click, the cursor menu displays a number of useful options for overriding dimension settings or assigning a different style.
When you change a setting in the Properties palette, you’re
You can use the Properties palette to turn on AutoCAD 2005’s new background mask feature, described in Chapter 9, for the text of individual dimensions: Select the dimensions, display the Text area in the Properties palette, and choose either Background or a specific color from the Fill Color dropdown list. Note that turning on background mask in the Multiline Text Editor window, as Chapter 9 tells you to do for regular (nondimension) text, does
The AutoCAD eXplode command on the Modify toolbar will blow a dimension apart, into a bunch of line and multiline text objects. Don’t do it! Exploding a dimension makes it much harder to edit cleanly and eliminates AutoCAD’s capability of updating the dimension text measurement automatically.
