Creating Transitions with Blends in Adobe Illustrator CS4
In Illustrator, a blend is a set of at least two objects that morph into each other. For example, when you're blending two objects, Illustrator generates new shapes between the two objects, making it seem as if one of the objects is turning into the other. The iterations that are created between the two main objects (also referred to as key objects) are called steps, and Illustrator gives you control over how many steps make up each blend (see Figure 1).
Figure 1 A blend in Illustrator consists of key objects and blend steps.
Although creating blends may seem like something reserved for highly specialized tasks, the reality is that you can use blends for many reasons. In fact, before gradients were introduced to Illustrator, blends were the only way you could create color gradations. Here's a list of some other common uses for blends in Illustrator:
- Creating shading effects. You can use blends to create photorealistic shading effects. Because blends can be created using any vector shape, you can create customized gradations not only in color but in shape (see Figure 2). This feature gives blends a distinct advantage over gradients.
Figure 2 By blending two shapes, you can get realistic shading in a way that's impossible with linear or radial gradients.
- Creating animations. When creating animations in Illustrator, you can use a blend to tween steps between objects, which saves you from having to create the necessary keyframes yourself (see Figure 3). Tweening is a term used in animation to define the steps that appear when showing movement, or one object morphing into another.
Figure 3 By blending two symbols with different opacity levels, Illustrator creates the necessary steps to create an animation.
- Distributing objects. If you need to repeat art across an area or along the curve of a path, you can use a blend to distribute a specific number of steps evenly.
You can't blend images or Area Type objects (text enclosed within a shape), but you can blend just about anything else—including symbols and groups. In fact, you can even blend between objects that have different Live Effects settings.
Creating a Blend
You can generate a blend in either of the following ways:
- Menu method. The quickest way to create a blend is to use the menu. Select at least two objects and choose Object > Blend > Make, or press Command-Option-B (Windows: Ctrl-Alt-B). With this method, Illustrator blends the bottom object in your selection with the next object up in the stacking order.
- Blend tool method. Creating a blend by using the Blend tool takes a few extra clicks of the mouse, but gives you extra ability to control the blend. Select the objects you want to blend, and then click the Blend tool in the Tools panel or press W. Click an anchor point in the first object to define where you want the blend to start, and click an anchor point in the second object where you want the blend to end. If you have more than two objects to blend, keep selecting an anchor point from each object until the blend is created.
This method allows you to control the order in which key objects appear in the blend. Additionally, if you click an anchor point near the top of one object and then choose an anchor point toward the bottom of the next key object, Illustrator rotates and modifies the intermediate steps of the blend to match the orientation of the anchor points.
Illustrator can have a maximum of 256 steps in a blend. The number of steps that appear in a blend has a direct impact on screen redraw speed, print performance, and file size.