Working with the Pathfinder Commands

Pathfinder commands let you take one vector shape and use it to modify the shape of another object. With these commands, it's easy to combine a rectangle and triangle into a house, cut a hole out of a circle to create a new moon, or divide and recolor circles into Olympic rings. As powerful as the original Pathfinder commands were when first released in 1993 in Illustrator 5, today's Pathfinders are even more amazing.

Pathfinders in Illustrator

Illustrator CS2 has several types of Pathfinder commands. The most obvious are the ones in the Pathfinder palette (see Figure 5-13), which is divided into two groups. The Shape Modes allow you to merge and combine objects without actually changing the original vector artwork. These are called non-destructive changes. The six Pathfinder command buttons on the bottom make actual cuts and changes to the objects. These are called destructive changes. You can convert an object from its non-destructive Pathfinder state to a permanent, destructive state by using the Expand button in the Pathfinder palette or pressing Option/Alt as you click the Shape Modes buttons. See Table 5-4 at the end of this section for a review of all the Pathfinder commands in the Creative Suite applications.

Figure 5-13. Illustrator CS2 Pathfinder palette

Table 5-4. Pathfinder Commands in CS2 Applications

To do this	Command in Illustrator	Command in InDesign	Command in Photoshop	Notes
Add shapes together	Add	Add	Add to Shape Area
Subtract frontmost object from backmost object	Subtract	Subtract	Subtract From Shape Area
Subtract backmost object from frontmost object	Minus Back	Minus Back	(N/A)
Create new object based on shape of intersection of objects	Intersect	Intersect	Intersect Shape Areas
Punch hole based on shape of intersection of objects	Exclude	Exclude Overlap	Exclude Overlapping Shape Areas
Divide objects into discrete shapes where they overlap	Divide	N/A	N/A
Remove parts of objects that are not visible	Trim	N/A	N/A	Does not merge objects with the same color
Remove parts of objects that are not visible and merge objects with the same colors	Merge	N/A	N/A
Divide objects where they overlap and remove any objects that lie outside the boundary of the top object	Crop	N/A	N/A
Divide object into individual line segments	Outline	N/A	N/A
Convert object into effect	N/A	Convert Shape commands	N/A	Applies effect to change shape of rectangular bounding box Shapes include rectangles (regular, rounded, beveled), ellipse, triangle, polygon, and lines

Illustrator CS2 also has Pathfinder commands in the Effects menu. These are similar to the commands in the Pathfinder palette, but they can be applied to single objects, groups, or all the objects on a layer. These effects are also non-destructive but can be expanded into permanent changes using the Object > Expand command.

Pathfinder Commands in InDesign

Compared to the non-destructive commands in Illustrator, InDesign's Pathfinder commands are a step back into the Dark Ages. However, InDesign's Pathfinder palette does contain a few extra goodies that you will need sooner or later (see Figure 5-14).

Figure 5-14. InDesign CS2 Pathfinder palette

The top five Pathfinder buttons work similarly to Illustrator's Pathfinder commands. But InDesign doesn't have live Shape Modes. Here, applying a Pathfinder command to objects permanently changes the shape of the path. There is no way to edit the original objects unless you invoke the Undo command.

However, the twelve Convert Shape buttons are similar to the Shape Modes in Illustrator, except that they only work on individual objects. When you apply any of the first nine Convert Shape buttons (Rectangle, Rounded Rectangle, Beveled Rectangle, Inverse Rounded Rectangle, Ellipse, Triangle, Polygon, Line, and Orthogonal Line), you apply an effect to change the shape of the object. The actual object is a rectangular bounding box. The shape of the object comes from the effect applied to that rectangular box. The other three buttons will open a path, close a path, or reverse the direction of a path.

What if you want to expand these premade shapes into actual vector paths, with honest-to-goodness anchor points instead of electronic instructions? No problem! One of the advances in InDesign CS2 is that the Pathfinder commands now honor the shape effects applied to objects.

Tip: Expanding a single shape into a discrete object

InDesign Pathfinder commands expand the shape effects into paths, but the commands require two shapes to work. What if you want to expand a single shape? Simply click the Open Path button and then the Close Path button. This expands the shape effect into an ordinary path.

Pathfinder Commands in Photoshop

Strictly speaking, Photoshop does not have Pathfinder commands or a Pathfinder palette. Using the default setting, Photoshop always creates a new shape layer as you draw with the vector-drawing tools. You can change this behavior using the shape-layer options in the Options bar (see Figure 5-15). These are similar to the Illustrator Shape Modes in the Pathfinder palette.

Figure 5-15. Photoshop CS2 Pathfinder-type controls

To use these Pathfinder-type controls, select the control before you draw. The default is to create a new shape layer each time a shape is created. The other options automatically add new shapes to the same layer. The options control whether the shapes combine with each other, subtract from each other, create an intersection where they overlap, or create a hole where they overlap.

You can change the control for each new object as you draw on the layer. For example, you can have two objects added together that a third object subtracts from the shape.

You can also change existing objects from one Pathfinder control to another. Use the Selection tool to select the objects, and then click the Pathfinder controls on the Options bar. You can mix and match these controls on the same layer so that, for example, some objects combine and others show intersections or exclusions.

The Pathfinder-type controls in Photoshop are non-destructive (similar to Illustrator's Shape Modes). You can move the paths around as needed to create new shapes. However, to make the effect permanent, click the Combine button in the Options bar.