What is the Polyline Command?
Very few people remember what it was like to do mechanical drafting before AutoCAD hit the market. When I talked to a colleague a few days ago it was amazing how much things had changed since the manual days. I took a mech drafting class or two in college, but, honestly, if you handed me a T square and a French curve, I’d probably wonder where the mouse buttons are.
One of the things that really brought home the difference between mechanical drafting the old way and AutoCAD is line segments and polylines. The Polyline tool is up on the Drawing toolstrip, next to the Draw tool., and looks sort of like a fish hook with dots along its length.
What does the Polyline Command do?
What polylines do is create line segments that have some level of automation and object awareness in them. You use the Polyline tool to draw shapes – each time you “complete” a shape, or part of a shape (and deselect it) it automatically groups all the segments into one item that can be clicked on, resized and dragged around. You can identify objects made by polylines by the blue “handles” or “grips” on the corners in the drawing area.
However, there’s more to polylines than grips and handles – remember the reminiscing about mechanical drafting? Well, one of the things that eats time for draftsmen doing it the old fashioned way is erasing and adjusting line segments, and getting those changes propagated across an entire drawing.
With polylines, that becomes much simpler – albeit a bit counter-intuitive. Because AutoCAD gives you the ability to enter coordinates to start polylines with, you can specify arcs, tangential segments, and stroke widths. Sometimes, this is much more efficient than drawing with the mouse – sometimes, you need to do some trial and error to make it work.
When you specify the start point, you’re given a choice for the next point on the line – an Arc/Halfwidth/Length/Undo/Width choice. You’ll be selecting the first letter of the word, in Upper Case text. To draw a blob (like a lake), enter A for Arc. The line segment immediately turns into an arc. You can select a bunch of other segments until it’s close to the shape you want; to close off the polyline object, enter CL to close the segments (note that this is a two letter command, and is case sensitive!)
Note also that when the Arc command is selected, you get a choice of options that pops up. You can play with the Radius, miter limits and a number of other options. The best way to find out what to do is to just play with the tools for a bit. It’s the equivalent of being a kid with magic markers all over again. Don’t worry about getting something productive out of it – learn where everything is and see what everything does for now.
Moving past Arcs, there are other traits that polylines have. One of the more useful ones is Width. After selecting the polylines command again, draw an object with a polyline, and hit W. You have the option to select the width of the polyline numerically. This is comparable to the stroke of the line with a pen nib (something else I’d forgotten about mechanical drafting!), and allows you to get almost calligraphic with your line weights. One of the neat things is that AutoCAD will ask you for the width of the start of the line, and then ask for the width of the end of the line – you don’t have to use the same width. This is a great way to get a lot of flexibility in drawing your line segments with this program, and the more you use it, the more uses you’ll see for it.
So what are you waiting for?
Start using the polyline command in your drawings today and stop wasting your precious time drawing things manually that don’t need to be.
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