Nearly once a week in the Illustration forum, somebody posts a message asking about “Open Paths.” Although the Illustration Training Manual contains a section on open paths (or shapes), the topic always comes up for clarification. This article will attempt to be the definitive word on the subject (see you in the forums). We’ll tell you why it matters, how to avoid open paths, and what the exceptions are. For designers and buyers, we’ll let you know what it all means to you.
Many a seasoned illustrator has never had to think twice about open shapes. As long as it looks the way it’s supposed to, who cares, right? If you’re happily using your own vectors on your web pages and print projects, and nothing funky happens, then it’s all good. Problems can arise, however, when you hand off that vector file to someone else. Say, for example, when you put it up for sale on iStock. Contributors have no control over who downloads our files, but we do need to control how we construct them, so there are no surprises on the buyer’s end.
All of the paths in this example are open, and have a thick black stroke. As you can see, even open paths can be “filled” with colors, gradients or patterns. It’s not a big deal if that’s the look you’re going for and only you are using the file. But here’s where it gets problematic.
Open paths becoming filled
This light blue square looks like a closed path, but once a heavier stroke is applied, you can see that the points don’t meet. Remember that a designer may want to enlarge the illustration or change the stroke width. If the shapes aren’t closed, an unexpected appearance may result. There are also some effects that behave differently on open shapes. Fixing all those paths on the designer’s or printer’s end can be time-consuming and costly.
Open paths become apparent with a heavier stroke
Unfilled open shapes are okay. That is, any path that has a stroke color but no fill color can remain open. Here is an example where I think it makes sense to leave the strokes as strokes:
The graph paper lines are .25 point thick, which is just about the smallest that will print. If a designer decides to scale down the illustration, those lines may become unprintable. Leaving them as strokes lets the designer/printer easily adjust the line weight. Keep the designer in mind when choosing to leave unfilled paths open.
Lines can remain open because they have a fill of "none"
IMPORTANT NOTE TO DESIGNERS: If you work with Illustrator®, be sure to check “Scale Strokes & Effects” in your Preferences. That way, when you enlarge or reduce an illustration, the strokes will remain proportionate.
Now that you know all about open paths and why they’re bad (and when they’re not), how do you find them in your illustration?
The easiest way is to use the free Select Menu plug-in by Graffix Software. Choose Select>Open Paths from the menu (better yet, assign a keyboard shortcut to it) and all of the open paths will show up. The plug-in won’t distinguish between filled and non-filled paths, it just shows you where they are.
Er, not so fast. If any open paths are locked or hidden, the plug-in won’t select them. Also, ruler guides are actually open paths, but the plug-in won’t select those for you either. (Guides shouldn’t be a problem in approving your files, but if you’re the persnickety type, you might want to delete all guides before submitting your file.)
The one iron-clad, fail-safe way to know whether there are open paths in your file is to use the Document Info panel (Window>Document Info) in Illustrator®. Here you will see a wealth of information about your file, including the number of paths, closed and open. From the flyout menu on the panel, check “Objects” and uncheck “Selection Only” to see the whole file at a glance.
Check “Selection Only” if you want to examine a particular selected piece of the file. If you’re having difficulty tracking down the offending path, you can use a process of elimination, using the Document Info panel. Select an object or layer of the file. If the panel shows that all paths are closed, hide those then move on to the next selection. And remember to delete the guides.
Okay, you’ve hunted them down, now how do you close them? If there are just a couple, most people use the Pathfinder functions to close the paths one-by-one. A newly-discovered trick is to select the Knife tool (the one with serrated edge), then drag a big circle around your illustration. Filled shapes will close; paths with a fill of “none” will remain open.
There are also various plug-ins and scripts for closing paths. Point Control (Mac only) is a plug-in that includes a “Close Paths” function.
There are a couple of scripts here (note: download will begin immediately), though they contain no documentation. Scripts must be installed in the Adobe Illustrator/Presets/Scripts folder. Once there, scripts will appear in the Scripts menu under the File menu. For more info on Illustrator scripting, there are several documents in the Scripting folder inside the Adobe Illustrator folder.
There are several things that will cause open paths even though you think they shouldn’t. And this often happens after saving the version 8 EPS. These include:
An expanded custom brush leaves behind an open path
We’ve all had this happen, and it burns every time. There are three reasons:
For one of the reasons above, or just a ghost in the machine, some paths became open when you saved the file. The only thing to do is save the EPS, close it, reopen it and check again. I know it’s an extra step, but it beats having to re-submit. Once you know where to look for open shapes and how to prevent them, your approval rate will increase!