The LINE command and the line entity

by Will on November 17, 2010

It doesn’t get much simpler than this does it. Does it…?

Well, no not really. But there are a few things that people generally don’t know, and there are some misconceptions about the LINE command that you should know about.

Normal Usage

After starting the LINE command you are prompted for a start point and an end point. Enter them as requested, and you’ve got yourself a swanky new line in your drawing. The LINE command repeats until cancelled by the user, assuming the end point of the last line is to be the start point of the new line. During a chain of lines you have the option to press ‘U’ for undo, which deletes the last line drawn, or ‘C’, which ends the command by joining the ends of the string of lines to form a closed loop.

Special Usage

Did you know that you do not have to give a start point? This is a fairly standard AutoCAD® thing, but if you press return at the prompt AutoCAD® will assume you want to start from the last point you entered. So if you drew some lines, ended the command but then wanted to continue drawing from the endpoint of the last line you drew, start the LINE command and press return at the first point prompt.

Ok its not that special, but it leads me to the extension of this idea. Lets assume the last object you drew was an ARC. If you now invoke the LINE command and press return at the first prompt, the start point is at the end point of the ARC, as you’d expect. But, the line is constrained to the tangent of the ARC, which could indeed be quite useful.

Other Information

There is often debate on whether it is better to by default use the LINE command or the PLINE command. The PLINE command offers additional functionality but at the cost of file size. I want to dispel the notion that polylines result in bigger file sizes, because it simply is not true. Yes, if you compare one polyline with one line, the polyline contains more information and therefore takes up more space. But, compare a string of lines to the same string of lines represented by a single polyline and you’ll get a different story. The reason for this is that a polyline stores the points as a list of coordinates. While its true that lines do the same, a string of lines means that there are many repeated coordinates because the ends of the lines are on top of each other. So in this instance the overhead of having a polyline is worthwhile because it stores the points more efficiently.

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