AutoCAD For Dummies - Ralph Grabowski

Скачать книгу

width means, “Display this segment using the normal, single-pixel width on the screen, and print as thin as possible.” How can you tell when your pen has run out of invisible ink? You can see the writing.

      4 Specify additional points by clicking or typing.After you specify the second point, AutoCAD adds the Close option to the prompt. The command line showsSpecify next point or [Arc Close Halfwidth Length Undo Width]: What you do next can get a little weird. If you invoke the Close option after selecting only the first and second points, PLine doubles back on itself and creates the second segment back over the first, unlike the Line command, which won’t. Normal practice would be to not invoke Close until you have created at least two non-collinear segments.

      5 Pick several points to create several line segments, and then enter W to start the Width option. Then set a new width, as shown in this command line sequence: Starting width <0.0000>: 5Specify ending width <5.0000>: Press Enter

      6 Pick several more points and note the line width of the new segments.

      7 Set the Width option again: Starting width <5.0000>: 15Specify ending width <0.0000>: 0

      8 Pick another point.You just created a cool arrowhead! Any time AutoCAD prompts for a length or distance, you can either type a value or you can show it what you want by picking two points in the drawing.

      9 After you finish drawing segments, press Enter to leave the figure open, or type C and press Enter to close it back to the start.AutoCAD draws the final segment and miters all the corners perfectly.

Schematic illustration of the optional extras.

      FIGURE 6-2: The optional extras.

      

After you create a polyline, you can adjust its segments by grip-editing any of the vertex points. See Chapter 11 for details on grip editing.

      In the following steps, I spice things up by adding an arc segment to a polyline.

      ALTERNATIVES TO THE LINE AND PLINE COMMANDS

      The Line and PLine commands work well for drawing a series of end-to-end single lines, but you may want to draw a series of double lines to represent, for example, the edges of a wall or roadway. Here are some options:

       Use the AutoCAD MLine command to draw multilines, which are a series of two or more parallel straight lines. The AutoCAD Multiline feature was full of limitations when it debuted way back in 1994 (in the notorious Release 13), and despite minor tweaks in AutoCAD 2006, it hasn’t improved significantly since then. It exists mostly for compatibility with MicroStation files. Look up the MLine and MLStyle commands in the AutoCAD online help system if you want to tangle with this feature, but be prepared to spend time experimenting, struggling, and (possibly) cursing. Don’t let small children near you.

       Use the PLine command to draw a single set of connected line or arc segments or both, and then use the OFFset command (described in Chapter 11) to create one or more sets of parallel segments.

       In AutoCAD LT only, use the DLine, or Double Line, command to draw pairs of parallel line or arc segments or both. Unlike MLine, DLine works well. AutoCAD LT doesn’t have the MLine command, which is more of a blessing than a limitation. AutoCAD, on the other hand, doesn’t have the DLine command. (Score one for the little brother!)
Curved segments in polylines are circular arcs that you can create while running the PLine command. AutoCAD can draw other kinds of curves, including ellipses and splines, but not in the PLine command.

      To draw a polyline that includes curved segments, follow these steps:

      1 Repeat Steps 1–4 in the preceding step list.

      2 To add one or more arc segments, type A, and then press Enter to select the Arc option.The prompt changes to show options for drawing arc segments. Most of these options correspond to the many ways of drawing circular arcs in AutoCAD; see the section on arcs in Chapter 7. The command line shows:Specify endpoint of arc or [Angle CEnter/CLose Direction Halfwidth Line Radius Second pt Undo Width]:

      3 Specify the endpoint of the arc by clicking a point or typing coordinates.AutoCAD draws the curved segment of the polyline. The prompts continue to show arc segment options.Specify endpoint of arc or [Angle CEnter/CLose Direction Halfwidth Line Radius Second pt Undo Width]:The options at this point are toSpecify additional points to draw more arc segments.Choose another arc-drawing method, such as CEnter or Second point.Return to drawing straight-line segments with the Line option.In this example, you draw straight-line segments. Perhaps the most useful of the alternative arc-drawing methods is Second pt. It gives you more control over the direction of the arc but at the cost of losing tangency of adjacent segments. (Sometimes, it’s best not to go off on a tangent, anyway.) If you want both ends of the arc segments to be tangent to the adjacent line segments, draw the polyline as straight-line segments and then use the Fillet command (described in Chapter 11) to add the arcs later.

      4 Type L and then press Enter to select the Line option.The prompt reverts to showing straight-line segment options.Specify next point or [Arc Close Halfwidth Length Undo Width]:

      5 Specify additional points by clicking or typing.

      6 After you’re finished drawing segments, either press Enter or type C and press Enter.

 Schematic illustration of a plethora of polylines.

      You could use the PLine or Line command to draw a rectangle, segment by segment. In most cases, though, you’ll find that using the special-purpose RECtang command is easier. The following steps show you how:

      1 Click the Rectangle button on the Draw panel of the Home tab, or type REC and press Enter. Can’t find a command? Some commands may be hidden in slideout panels on the Ribbon interface. Many Ribbon panels display a down-facing arrowhead beside the name of the panel. Click the arrowhead to see a collection of related but less-used commands. Still can’t find the command? Some Ribbon command buttons may be hidden under others in the same category. AutoCAD remembers the last one you used. For example, you may find POLygon under RECtangle or vice versa. AutoCAD starts the RECtang command and prompts you to specify a point for one corner of the rectangle. The command line displays the prompt:Specify first corner point or [Chamfer Elevation Fillet Thickness Width]: You can add fancy effects by using additional command options. The default options work best for most purposes. Look up RECTANG in the AutoCAD help system if you want to know more about the options.

      2 Specify the first corner by clicking a point or typing coordinates.AutoCAD prompts you to specify the corner of the rectangle that’s diagonally opposite from the first one.Specify other corner point or [Area Dimensions Rotation]:

      3 Specify the other corner by clicking a point or typing coordinates.The rectangle is drawn after you specify the second corner point. If you know the size of the rectangle that you want to draw (for example, 100 units long x 75 units high), type D to enter the Dimensions option, and

Скачать книгу