If you were to ask me what the best feature in Illustrator is, I would tell you the Pathfinder functions. One of the greatest time-saving features in Illustrator, the Pathfinder commands are a set of powerful path-editing functions found under the Object menu (see Figure 13.1). In this hour we cover these functions, including:
Once a set of filters (since version 5.5), the Pathfinder commands enable you to quickly perform complex path functions on multiple objects. Later, we describe each function, as well as present an example to demonstrate what each command does.
The first group of Pathfinder commands is used to make complex shapes out of simple ones (see Figure 13.2). You can quickly create unique art by using Illustrator's basic drawing tools, and then modify them using these Pathfinder commands.
Choosing the Pathfinder commands.
The first set of Pathfinder commands.
The most commonly used Pathfinder command, Unite simply takes all selected objects and combines them into one object. Unite doesn't just group the objects together; it "glues" them all together, leaving just one large shape, removing all paths that overlap (see Figure 13.3). When running the Unite command, the final object is automatically brought to the front. Whatever color the front-most object in your selection is becomes the color of the final, united object.
The Unite command combines objects.
The Intersect function is used on two objects that overlap each other. After you choose Intersect, the area in which the objects overlap remains as one combined path, and the rest of each object is deleted (see Figure 13.4). This command won't work if you have more than two objects selected.
The overlapping portion remains.
The exact opposite of the Intersect command, Exclude takes two objects that overlap each other and deletes the areas where they overlap (see Figure 13.5). The remaining objects are grouped together. This command won't work if you have more than two objects selected.
Removing the overlapping portion.
Minus Front takes two objects and subtracts the front-most object from the object behind it (see Figure 13.6). This command is great for cutting little shapes or bits out of larger objects. If the front image fits within the back image, Minus Front creates a compound path for you. It works a lot like a cookie cutter, only what you end up seeing is what's left of the dough, not the cookie. This command won't work if you have more than two objects selected.
Removing the front object, and whatever is behind it.
The reverse of Minus Front, Minus Back subtracts part of an image based on the image behind it (see Figure 13.7). Going back to the cookie cutter example, this filter would produce the cookie. This command won't work if you have more than two objects selected.
Removing the rear object and taking whatever is in front of it with it.
The next group of Pathfinder commands deals with splitting objects into parts or deleting unwanted parts of objects (see Figure 13.8).
The second batch of Pathfinder commands.
Divide takes any overlapping shapes and cuts them up into separate shapes wherever they overlap (see Figure 13.9). An invaluable tool, Divide enables you to quickly split up objects without once having to use the Scissors tool. Also, using the precision of drawn shapes, you can perform careful slices and divisions without using the clumsy Knife tool.
Divide turns each intersecting part into a separate image.
Divide looks at each object and divides each overlap individually, so it makes no difference if you're dividing compound paths, groups, or whatever--they all become individual shapes. After Divide runs, all objects are grouped together. You have to ungroup them if you want to work with each piece separately.
Choosing the Outline command converts all shapes to outlines (see Figure 13.10), and also divides the lines where they intersect (similar to a Divide command for strokes).
The Outline command.
The Trim command removes the parts of the back object that are behind the front objects. It also removes the stroke (see Figure 13.11).
Running the Trim command.
The Merge command operates differently, depending on the fills of the selected objects. If they're all the same, it's similar to Unite, making them one object. If they're all different, it works like the Trim command, mentioned above. If some of the objects are filled the same, the like objects are united, and the rest are trimmed (see Figure 13.12).
Running the Merge command.
The Crop command removes any parts of selected objects that are not directly underneath the front-most object (see Figure 13.13). The final result of the Crop command is exactly what a mask would do. The only difference is, the Crop command actually deletes the art that is not visible, unlike a mask, which just covers it up. Be careful before you run this command, because you cannot retrieve the artwork that is cropped out.
The Crop command.
One of the most common uses for these two commands is for simulating transparency effects. These filters mix overlapping colors.
The Hard command takes overlapping objects and mixes the values of the colors where the shapes overlap (see Figure 13.14).
Mixing colors with the Hard command.
The Soft command is identical to the Hard command, except for the fact that you can control how the colors are mixed by specifying a percentage. Although Hard might produce an image that looks transparent, Soft might be used to create an object that appears translucent (see Figure 13.15).
Creating a translucent effect with the Soft command.
The Trap command takes selected art and traps it as specified (see Figure 13.16). Many printers today require that you provide artwork that is trapped properly. It is best to speak with your printer and discuss your options. If you need to trap your own artwork, make sure your printer provides you with the settings he needs.
The Pathfinder Trap dialog box.
A computer is perfect. When you draw a square of one color and place it right up against another square of another color, you get two squares touching each other, with one color ending where the next one begins.
Out in the real world, however, this is not always so easy. A printing press is (usually) a large machine, and it's nearly impossible for every color to print in the exact same place every time. What usually happens, in our case with the squares, is that there is a slight shift between the colors that enables a sliver of white, or whatever color the paper is, to sneak through between the two squares.
To get around this problem, printers rely on a process called trapping. By slightly extending the colors (called choking and spreading) and having them overprint each other, the squares do not just touch each other, but actually overlap a bit. Now, if the press shifts a bit, there is enough of an overlap of color that a white sliver won't show through. By setting a color to overprint, you are instructing the colors to print over each other, achieving the trap. Because the Trap command makes changes to your artwork, it's a good idea to save a copy of your file before you use it. Also, save it for the last step to make for easier editing.
Because we're mentioning traps, I thought I'd also show you how you can specify overprints through Illustrator's Attributes palette (see Figure 13.17). After you select an object, you can choose to overprint the fill or the stroke by checking the appropriate box.
The Attributes palette.
Before we wrap things up, I'd just like to point out that (Command-4)[Control-4] performs the last-used Pathfinder command. Many times when editing multiple objects, you need to apply Pathfinder commands over and over again, and it's a bit of a pain going all the way into the Pathfinder submenu so often. (Extensis VectorTools 2.0 has a floating palette with all of Illustrator's Pathfinder commands).
Pathfinder rules! Today we learned how the Pathfinder commands slice, dice, mince, chop, and mix together all of our favorite vector recipes. We even dived right into a conversation about trapping and overprinting. And if all this wasn't enough for you, the next hour talks about using text in Illustrator.
Trapping--The process of spreading or extending colors to compensate for printing press error.
Overprinting--Technical term for forcing one color to print on top of another.
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