Aligning Objects Using Object Snap Tracking and Tracking Points


Osnaps are great for selecting exact locations directly on existing objects, but what if you want to find a point that is aligned with an object but not necessarily on the object? Object snap tracking, or osnap tracking, is like an extension of object snaps that allows you to align a point to the geometry of an object instead of just selecting a point on an object. This alignment point is referred to as a tracking point since the cursor "tracks" from the selected osnap point.

With osnap tracking you can select a point that is exactly at the center of a rectangle. In the following exercise, you'll place a circle in a rectangle to see how osnap tracking works firsthand.

The osnap tracking feature is not available in AutoCAD LT 2008. If you are using LT, you can use the temporary tracking feature described later in this chapter.

First, make sure running osnaps are turned on and that they are set to the Midpoint option. Then make sure osnap tracking is turned on. The following steps describe how to do this:

  1. Right-click the Otrack button in the status bar, and choose Settings from the shortcut menu to open the Drafting Settings dialog box (see Figure 2.23) at the Object Snap tab.

  2. Make sure the Midpoint option in the Object Snap Modes group is checked. Other osnap modes might also be checked. You can leave them on.

  3. Also make sure that Object Snap On and Object Snap Tracking On are both checked. Click OK.

image from book
Figure 2.23: The Drafting Settings dialog box

Now you're ready to draw:

  1. Draw a rectangle large enough to fill most of the drawing area with some margin around the outside, as shown in Figure 2.24.

  2. image from book Click the Circle tool in the 2D Draw control panel, or enter C.

  3. At the Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: prompt, enter C, or right-click and choose Center from the shortcut menu.

  4. Move your cursor to the top, horizontal edge of the rectangle, until you see the Midpoint ToolTip.

  5. Move the cursor directly over the Midpoint osnap marker. Without clicking, hold the cursor there for a second until you see a small cross appear. Look carefully because the cross is quite small. This is the osnap tracking marker.

    image from book

    You can alternately insert and remove the osnap tracking marker by passing the cursor over it.

    Now as you move the cursor downward, a dotted line appears, emanating from the midpoint of the horizontal line. The cursor also shows a small x following the dotted line as you move it.

    image from book

  6. Move the cursor to the midpoint of the left vertical side of the rectangle. Don't click, but hold it there for a second until you see the small cross. Now as you move the cursor away, a horizontal dotted line appears with an x following the cursor.

    image from book

  7. Move the cursor to the center of the rectangle. The two dotted lines appear simultaneously, and a small x appears at their intersection.

    image from book

  8. With the two dotted lines crossing and the x at their intersection, click to select the exact center of the rectangle.

  9. At the Specify radius of circle or [Diameter]: prompt, click a point anywhere to finish the circle. The radius doesn't really matter here. The circle appears in the exact center of the rectangle, as shown in Figure 2.25.

image from book
Figure 2.24: Draw this rectangle to practice using osnap tracking.

image from book
Figure 2.25: The completed circle centered on the rectangle

Although you used the Midpoint osnap setting in this exercise, you are not limited to only one osnap setting. You can use as many as you need to in order to select the appropriate geometry. You can also use as many alignment points as you need, although in this exercise, you used only two. If you want, erase the circle, and repeat this exercise until you get the hang of using the osnap tracking feature.

As with all the other buttons in the status bar, you can turn osnap tracking on or off by clicking the Otrack button. You can also press F11.




Introducing AutoCAD 2008
Introducing AutoCAD 2008
ISBN: 0470121505
EAN: 2147483647
Year: 2007
Pages: 147
Authors: George Omura

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