Polylines - creating and editing, Revision Clouds | ||||||||||||||||||||||
A polyline is an object in AutoCAD that consists of one or more line (or arc) segments. A rectangle is an example of a polyline that you are already familiar with. As you've seen, it is one object that can be modified and worked with easier than four separate lines. Polylines are created using the POLYLINE command, invoked by typing PL at the command line. To draw a simple polyline, draw it as though you are using the line command. The only difference is that it is one object instead of many. Polylines have some unique qualities that make them very useful:
Command: PL PLINE Remember that any time you want to choose an option, you type in the Capitol letter of that option. One important tool is the Close option. This truly closes a polyline, which is different that just having two ends meeting at the same point - it's like welding the ends together. A closed polyline is required for extruding into 3-D space and other modifications. If you use the C option while drawing to complete your polyline, it will automatically be closed. The Spline option allows you to draw a shape of lines using arcs and/or straight lines and then change them into one flowing curve. (Spline is also a separate command on its own.) Also by changing the width of a polyline, you can get some different looks to your lines. Look at the examples below and then practice drawing polylines and try some of the options available. Below is a sample drawing you can reproduce using a polyline (it could represent a slot to be cut out with a CNC router. First, think about how you would draw it using lines, arcs and circles. Here's how you draw it using one polyline:
Command: PL PLINE Remember DDE? Start by entering your first point, then (with Ortho or Polar on) move your cursor to the right and type 5 <ENTER>then A <ENTER> for arc and move your cursor up and type 2 <ENTER> then type L <ENTER> (to go back to straight lines) and more your cursor to the left and type 5 <ENTER> then back to arc (A <ENTER>) and then type CL to close the polyline. Wow! That was easy! To edit a polyline, use the PEDIT command or type PE at the command line. Command: PE PEDIT Select polyline or [Multiple]:Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype gen/Undo]: One of the most common editing tools is the Join (J) option. Use this to combine two or more polylines and their endpoints. Use the LINE command to draw a line from 0,0 to 5,5. Now use the line command to draw a line from 5,5 to 8,5. This will leave you with 2 line objects that share a common point (5,5). Start the PEDIT command (PE) and select one of the lines. AutoCAD will ask you if you want to turn it into one, select Y <enter>. Command: PE PEDIT Select polyline or [Multiple]:
Select objects: <select the other line>
Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype Now you have one object (a polyline). This is a handy tool to use for editing. Now the shape is complete and you can offset it, scale it, etc., as one object. In 3D, you could also extrude it (if it is closed). Once you have a polyline, it is sometimes useful to break it into the individual segment. For example, you might want to offset segments by varying distances.. To do this, use the Explode command. It is used to separate many other AutoCAD objects as well such as blocks. Polylines are useful - try to use them whenever possible. Sometimes you can draw the outside walls of a building, offset the polyline for the wall thickness, then explode both of them for more versatility.
Revcloud (Revision Cloud) Another version of the Polyline command is the Revcloud (Revision Cloud) command. This is something you don't want to see on your drawings when the boss reviews your work. A Revcloud is used to highlight problems or errors in a drawing. You might also want to create a Revcloud to highlight a question you have with your own work. To create a revcloud, start the command. Then set the arc length to about 12 for an architectural drawing, or test out different arc lengths. Command: REVCLOUD Minimum arc length: 96' Maximum arc length: 96' Style: Normal Specify minimum length of arc <96'>: 12 Specify maximum length of arc <1'>: <ENTER>
Specify start point or [Arc length/Object/Style] <Object>: You might have ended up with something like this:
One thing with revclouds is that it can be hard to define a specific area clearly. Therefore, you have another option for creating accurate, clean revclouds like the one in the first example. Start by drawing a rectangle over the area you want to highlight, then start the Revcloud command and choose the Object option. Select the rectange and press enter to end the command. This will work on most AutoCAD objects. |