Adobe Illustrator CS2 – Working with Layers

Layers are nearly identical to groups in concept, but they offer more flexibility and functionality. Whereas groups are used to combine design elements in a file, layers also allow you to organize and combine elements within a file. Just as groups can be nested within each other, so can layers. And just as groups are containers that hold contents within them, layers are containers as well. In addition, layers, just like groups, can also have attributes applied to them. As we explore the power of layers in Illustrator, all of these concepts will come to light.

The Layers Palette

You’ll start learning to use layers by taking a look at the Layers palette and learning some of its simple functions. Then you’ll put together everything that you’ve learned in this chapter to take full advantage of the power found in the Layers palette.

The Significance of Layers

Don’t be fooled into thinking that layers are just for making files neat and organized. Quite the contrary, a file that takes advantage of using layers can benefit from many other features as well.

  • Layer clipping masks. Illustrator has the ability to make the topmost object in a layer a mask for all items within that layer.
  • PDF layers. Illustrator can export PDF files with layers intact, allowing users in Adobe Acrobat or Adobe Reader to interactively turn on and off those layers. Additionally, InDesign CS2 has the capability to control the visibility of PDF layers.
  • Photoshop export. When exporting an Illustrator file to a PSD file, you can choose to have layers preserved, thus making your file easier to edit when you bring it into Photoshop.
  • Transparency. There are times when artwork with transparency can result in files that look less than perfect when printed on a high-resolution press—if the file is built in a certain way. Using layers can significantly reduce the number of issues you might encounter when using transparency features.
  • Animation. When creating art for frame-based animations, like those used in GIF and SWF (Flash) animations, Illustrator layers serve as frames. Layers are also integral when you are creating art that will be animated in programs like Adobe After Effects.
  • CSS (Cascading Style Sheets). Illustrator layers can be exported as CSS Layers when you’re creating web layouts and SVG graphics, allowing for greater flexibility and better support for browser standards.
  • SVG (Scalable Vector Graphics). Illustrator layers serve as basic building blocks when you’re creating files that are going to be saved as SVG. Providing structure for SVG files can help make it easier to animate and edit the SVG files in a web or wireless environment.
  • Variables. Illustrator’s XML-based variables feature relies on the organization of layers in your document. Object visibility and naming conventions are all done through the Layers palette.

There are plenty of other good reasons to use layers in Illustrator, and you’re sure to find yourself using layers more and more.

By default, all Illustrator documents are created with a single existing layer, called Layer 1. The buttons across the bottom of the palette are used to activate clipping masks (which we’ll cover in detail in Chapter 5, Brushes, Symbols, and Masks), create new layers and new sublayers, and to delete layers. To the left of each layer are two boxes—the box on the far left controls layer visibility, whereas the other box enables locking.

Double-clicking a layer enables you to specify several settings for that layer:

  • Name. Every layer can have its own distinct name. Layer names are important when you’re creating SVG files and generally make files easier to work with. Naming layers is especially important when you’re designing templates. A file littered with layers named Layer 1, Layer 2, Layer 3, can make editing a challenging task.

    Note

    Option-click (Alt-click) the visibility icon of a Layer to hide all other layers with one click. Option-click (Alt-click) once more to show all layers again. The same shortcut applies to the lock icon as well. To change layer visibility for multiple layers, you can click and drag across several layers.

  • Color. This setting is a bit deceiving because it doesn’t add a fill color to the layer but instead defines the selection color used for the layer. When you select an object in Illustrator, the path of that object is highlighted so that you see what is selected. By assigning different colors to each layer, you can tell what objects belong to which layer by selecting the object and observing the highlight color. Setting a layer color to black or really light colors generally isn’t a good idea because you won’t be able to differentiate a selection from a regular path.
  • Template. This setting is used specifically when you want to manually trace placed images. Setting a layer as a Template automatically locks the layer and sets the Dim Images setting to 50 percent. Although this makes it easier to see and draw over placed images, the new Live Trace feature makes this option less important.
  • Show. This setting controls layer visibility (whether the art on a layer is shown or hidden) and performs the same function as clicking the show/hide icon in the Layers palette.
  • Preview. This setting controls the preview setting for the chosen layer. By default, Illustrator’s Preview mode is turned on, but unchecking this option displays the layer in Outline mode.
  • Lock. This setting controls layer locking and performs the same function as clicking the lock/unlock icon in the Layers palette itself. Locking a layer effectively prevents you from selecting any object on that layer.
  • Print. By default, all layers in a file will print. However, Illustrator allows you to uncheck this option to create a nonprinting layer. This can be useful when you want to add instructions to a template file or to explain how a file should be folded or printed, but you don’t want those instructions to print. Layers that have the Print option turned off appear italicized in the Layers palette.
  • Dim Images to. This option allows you to define an opacity setting for placed images. By making placed images dim, you can make it easier to manually trace them. This feature is often used in tandem with the Template function.

The Layer Options dialog allows you to specify settings for each layer—most notably, the name of the layer.