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Autocad for dummies - Byrnes D.

Byrnes D. Autocad for dummies - Wiley publishing, 2007. - 435 p.
Download (direct link): autocad2006.pdf
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Unlike a lot of AutoCAD drawing commands, LINE doesn’t offer a bunch of potentially confusing options. There’s a Close option to create a closed polygon and an Undo option to remove the most recent segment that you drew.
Like all drawing commands, LINE puts the line segments that it draws on the current layer and uses the current color, linetype, lineweight, and plot style properties.
^ Make sure that you’ve set these properties correctly before you start drawing. (We recommend that you set color, linetype, lineweight, and plot style to ByLayer.) See Chapter 5 for information on setting the current properties with the Properties toolbar.
^ When you’re doing real drafting as opposed to just experimenting, make sure that you use one of AutoCAD’s precision tools, such as object snaps, typed coordinates, or tracking, to ensure that you specify each object point precisely. Chapter 5 describes these tools.
Follow these steps to draw a series of line segments by using the LINE command:
1. Set the desired layer current, and set other object properties that you want applied to the line segments that you’ll draw.
2. Click the Line button on the Draw toolbar.
AutoCAD starts the LINE command and prompts you.
Specify first point:
138 Part II: Let There Be Lines
3. Specify the starting point by clicking a point or typing coordinates.
Remember to use one of the precision techniques described in Chapter 5 if you’re doing real drafting. For the first point, object snap, snap, tracking, and typing coordinates all work well.
AutoCAD prompts you to specify the other endpoint of the first line segment. The command line shows:
Specify next point or [Undo]:
You can also see command prompts at the Dynamic Input tooltip beside the crosshairs by pressing the down-arrow key. The arrow icon on the dynamic cursor tooltip is your indicator that there are options available.
4. Specify additional points by clicking or typing.
Again, use one of the AutoCAD precision techniques if you’re doing real drafting. For the second and subsequent points, all the techniques mentioned in the previous step work well, plus ortho and direct distance entry.
After you specify the third point, AutoCAD adds the Close option. The command line shows:
Specify next point or [Close/Undo]:
5. When you’re finished drawing segments, end with one of these steps:
• Press Enter, or right-click anywhere in the drawing area, and choose Enter to leave the figure open.
• Type C and press Enter, or press the down arrow on your keyboard and choose Close from the menu (as shown in Figure 6-1), to close the figure.
AutoCAD draws the final segment. The command prompt indicates that the LINE command is finished:
Command:
Connect the tines with polyline
The LINE command is fine for some drawing tasks, but the PLINE command is a better, more flexible choice in many situations. The PLINE command draws a special kind of object called a polyline. You may hear CAD drafters refer to a polyline as a pline because of the command name. (By the way, PLINE is pronounced to rhyme with beeline — in other words, it sounds like the place you stand when you’ve drunk a lot of beer at the ball game.)
Chapter 6: Where to Draw the Line 139
Figure 6-1:
Line it up — drawing line segments with the LINE command.
The most important differences between the LINE and PLINE commands are these:
The LINE command draws a series of single line segment objects. Even though they appear on the screen to be linked, each segment is a separate object. If you move one line segment, the other segments that you drew at the same time don’t move with it. The PLINE command, on the other hand, draws a single, connected, multisegment object. If you select any segment for editing, your changes affect the entire polyline. Figure 6-2 shows how the same sketch drawn with the LINE and the PLINE commands responds when you select one of the objects.
Use the PLINE command instead of LINE in most cases where you need to draw a series of connected line segments. If you’re drawing a series of end-to-end segments, there’s a good chance that those segments are logically connected — for example, they might represent the outline of a single object or a continuous pathway. If the segments are connected logically, it makes sense to keep them connected in AutoCAD. The most obvious practical benefit of grouping segments together into a polyline is that many editing operations are more efficient when you use polylines. When you select any segment in a polyline for editing, the entire polyline is affected.
The PLINE command can draw curved segments as well as straight ones.
140 Part II: Let There Be Lines
You can add width to each segment of a polyline. Polyline segment width is visually similar to lineweight, except that polyline segment width can be uniform or tapered. The ability to create polyline segments with line widths was more important in the old days before AutoCAD had lineweight as an object property. People used to draw polylines with a small amount of width to show the segments as somewhat heavier than normal on plots. Nowadays, it’s easier and more efficient to achieve this effect with object lineweights (as described in Chapter 5) or plot styles (as described in Chapter 13).
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