When Is a Line Not a Line?

When is a line not a Line? When it is a Pline or a Spline!

So, we all know what a Line is. It’s the most basic of elements in a DraftSight drawing. As you can see below, each segment of a line is its own individual entity. You can erase any segment of the lines in the image below without earasing the others.

So, what is a Pline or Polyline? Well, a Pline is a series of connected Lines, so, unlike in the example above, each segment of it is not and individual entity. If you click on one segment of the Pline below and erase it, the whole Pline will be erased.

Finally, we are on to Splines. So, just what is a Spline? To quote the DraftSight help file, “A Spline is a smooth curve that is fit to a set of points. You can create a non-uniform rational B-spline or NURBS curve for any number of fit points. You can also fit the Spline to the specified points within a specified tolerance value.”

Like a Pline, all segments of a Spline are connected, what ever you do to one segment, affects the others.

A Spline should not be confused with an Arc. An Arc has only 3 points and has a uniform radius. You can see the difference in the animation below.

So that, very briefly, is the difference between a Line, Pline and a Spline in DraftSight. 

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MJ Smyth
The first time I used CAD, it was on a DOS PC with an 8088 processor, 640K of memory and a Hercules Mono Graphics Card... That, well that was a long long time ago. I switched to DraftSight the day it was released and haven't looked back!