AutoCAD 2005 for Dummies

drawing area:

 • Right-clicking displays menu options for the current command (or common commands and settings when no command is active).

 • Shift+right-clicking always displays the same object snap cursor menu.

  AutoCAD 2005 includes a new Mid Between 2 Points (M2P) object snap mode, which finds the point lying exactly halfway between two other points. You should use precision techniques, such as other object snaps, to select the two points.

Run with object snaps

Often, you use an object snap mode (such as endpoint) repeatedly. Running object snaps address this need. These steps set a running object snap:

1. Right-click the OSNAP button on the status bar.

2. Choose the Settings option.

The Object Snap tab on the Drafting Settings dialog box appears, as shown in Figure 4-13.

Figure 4-13: Grabbing multiple object features is an osnap.

3. Select one or more object snap modes by checking the appropriate boxes.

4. Click OK to close the dialog box.

You click the OSNAP button on the status bar to toggle running object snap mode off and on. After you turn on running object snap, AutoCAD hunts for points that correspond to the object snap modes you checked in the Drafting Settings dialog box. As with single-point object snaps, AutoCAD displays a special symbol — such as a square for an endpoint object snap — to indicate that it has found an object snap point. If you keep the cursor still, AutoCAD also displays a ToolTip that lists the kind of object snap point.

Use single point or running object snaps to enforce precision by making sure that new points you pick coincide exactly with points on existing objects. In CAD, it’s not good enough for points to almost coincide or to look like they coincide. AutoCAD knows the difference between “looks the same” and “is the same,” and will cause you untold amounts of grief if you try to make do with “looks the same.” You lose points, both figuratively and literally, if you don’t use object snaps or one of the other precision techniques covered in this chapter to enforce precision.

Other precision practices

The following are some other AutoCAD precision techniques (refer to Table 4-2, earlier in this chapter):

? Snap: If you turn on snap mode, AutoCAD constrains the cursor to an imaginary rectangular grid of points at the spacing that you’ve specified. Follow these steps to turn on snap mode:

 1. Right-click the SNAP button on the status bar.

 2. Choose the Settings option.

The Snap and Grid tab on the Drafting Settings dialog box appears.

 3. Enter a snap spacing in the Snap X Spacing field and then click OK.

Click the SNAP button on the status bar or Press F9 to toggle snap mode off and on. To use snap effectively, change the snap spacing frequently — changing to a smaller spacing as you zoom in and work on smaller areas. You often need to toggle snap off and on, because selecting objects and some editing tasks are easier with snap off.

? Ortho: Ortho mode constrains the cursor to move at right angles (orthogonally) to the previous point. Click the ORTHO button on the status bar or Press F8 to toggle ortho mode off and on. Because technical drawings often include lots of orthogonal lines, you’ll use ortho mode a lot.

? Direct distance entry: This “point and type” technique is an easy and efficient way to draw with precision. You simply point the cursor in a particular direction, type a distance at the command line, and press Enter. AutoCAD calls it “direct distance entry” because it avoids the indirect command line method of specifying a distance by typing relative or polar coordinates. (I describe this older method earlier in this chapter.) You can use direct distance entry any time the crosshair cursor is anchored to a point and the command line prompts you for another point or a distance. You’ll usually use direct distance entry with ortho mode turned on, to specify a distance in an orthogonal direction (0, 90, 180, or 270 degrees). You also can combine direct distance entry with polar tracking to specify distances in non-orthogonal directions (for example, in angle increments of 45 degrees).

? Object snap tracking: This feature extends running object snaps so that you can locate points based on more than one object snap point. For example, you can pick a point at the center of a square by tracking to the midpoints of two perpendicular sides. (AutoCAD LT lacks the object snap tracking feature.)

? Polar tracking: When you turn on polar tracking, the cursor jumps to increments of the angle you selected. When the cursor jumps, a ToolTip label starting with Polar: appears. Right-click the POLAR button on the status bar and choose the Settings option to display the Polar Tracking tab on the Drafting Settings dialog box. Select an angle from the Increment Angle drop-down list and then click OK. Click the POLAR button on the status bar or press F10 to toggle polar tracking mode off and on.

? Polar snap: You can force polar tracking to jump to specific incremental distances along the tracking angles by changing the snap type from Grid snap to Polar snap. For example, if you turn on polar tracking and set it to 45 degrees and turn on polar snap and set it to 2 units, polar tracking jumps to points that are at angle increments of 45 degrees and distance increments of 2 units from the previous point. Polar snap has a similar effect on object snap tracking.

To activate polar snap, follow these steps: 

 1. Right-click the SNAP button on the status bar.

 2. Choose the Settings option.

The Snap and Grid tab on the Drafting Settings dialog box appears.

 3. Click the Polar Snap radio button, type a distance in the Polar Distance edit box, and then click OK.

When you want to return to ordinary rectangular snap, as described at the beginning of this list, select the Grid Snap radio button in the Drafting Settings dialog box.

  If you’re new to AutoCAD, its wide range of precision tools probably seems overwhelming at this point. Rest assured that there’s more than one way to skin a cat precisely, and not everyone needs to understand all the ways. You can make perfectly precise drawings with a subset of AutoCAD’s precision tools. I recommend these steps:

1. Get comfortable with typing coordinates, ortho mode, direct distance entry, and single point object snaps.

2. Become familiar with running object snaps and try snap.

3. After you have all these precision features under your belt, feel free to experiment with polar tracking, polar snap, and object snap tracking.

  It’s easy to confuse the names of the snap and object snap (osnap) features. Remember that snap limits the cursor to locations whose coordinates are multiples of the current snap spacing. Object snap (osnap) enables you to grab points on existing objects, whether those points happen to correspond with the snap spacing or not.

Chapter 5 Where to Draw the Line

In This Chapter

? Drawing with the AutoCAD drawing commands

? Lining up for lines and polylines