Illustrator Layer Highlights

Because it's designed to create complex vector artwork, Illustrator handles layers in some unique ways. You can create template layers for tracing images, toggle a layer between Outline and Preview modes, and set layer printing.

Creating Template Layers

Sometimes you may want to use a piece of bitmapped artwork as the basis for creating a vector drawing. For example, you've captured an image with a digital camera or scanned a photograph, but you want to render the bitmap as line art. One way of utilizing the bitmapped artwork is to use the Live Trace command in Illustrator CS2. (We describe this feature in "Special Vector Tools in Illustrator" in Chapter 5, "Getting to the Point of Vector Graphics.") But the more traditional way is to place a bitmapped file onto an Illustrator template layer and manually trace the image with the Pen tool. If you're good with the Pen tool, this method may still produce the best result.

To create a template layer, choose File > Place, and choose the image file you want to trace, placing it on the currently selected layer. Then double-click the layer in the Layers palette. In the Layer Options dialog box, check Template, and then click OK (Figure 12-15, left). By default, all images on this layer are dimmed to 50% opacity (which can be adjusted), and the layer is locked. Create a new layer and use the Pen tool to trace the outlines of the image (Figure 12-15, right). Note that the Template layer shows a special layer icon in the left column of the Layers palette.

Figure 12-15. You can turn any layer into a template layer to trace an image (left). The image will be dimmed and locked to allow tracing on a layer above it (right).

Previewing and Outlining Layers

Just as Illustrator provides two modes of viewing entire artwork files Preview and Outline you can toggle the view status of individual layers, sublayers, and objects. Check the Preview check box in the Layer Options dialog box to toggle this status.

(For more on the value of switching between these views, see "Highlights of the Illustrator Interface" in Chapter 7, "Managing and Customizing the Interface.")

Printing and Not Printing Layers

Turning on and off the printing status of layers is useful when you're creating versioned files. At the time of printing, only layers with the Print status turned on will print. You can control the printing status of Illustrator artwork on a layer-by-layer basis. To make a layer nonprinting, uncheck the Print check box in the Layer Options dialog box.

Tip: Create Animations and Sequences

Illustrator allows distributing multiple objects each onto their own layer. This may be useful for creating Flash animations, for example. Highlight a group or layer in the Layers palette. To release each object to its own layer, choose Release To Layers (Sequence) from the palette menu. To release objects to layers and create a cumulative sequence, choose Release To Layers (Build) from the palette menu.