Illustrator has no single drawing tool similar to Photoshop’s airbrush. You can add transparency and Gaussian Blur effects to an existing stroke or add them to a stroke that uses a brush to get a similar appearance. For more advanced airbrush techniques, try using a blend between two circles, then using Object > Blend > Replace Spine to make that blend follow a drawn path. You can then change the colour, size, transparency, or blur on either end of the blend to change the brush stroke at any time.
See this PDF for one approach. The subject was really more about exploring ways to exploit Isolation Mode, but it does so in the context of a poor-man's "airbrush" effect.
I want the clean, vector lines of Illustrator with the yummy fuzzy airbrush tool.
In reality, then, you're not wanting vector artwork to look like vector artwork. Here's the thing:
Vector artwork, is by its fundamental nature "hard edged." That's one of its advantages and one of its disadvantages. Soft-edged fuzzy effect (and its sister, texture) is one of the mainstays of raster imaging. It's one of the main reasons why there are two primary kinds of computer graphics.
Historically, soft edges and graduations are primarily done with Blends and Graduated Fills. A Blend is really just a semi-automated stack of multiple paths with incrementally changing color. Grad fills are mathematically-defined variations of a path's fill color across the path. Generally speaking, grad fills are limited to a small set of geometric shapes. For most of Illustrator's history that was a very limited set: linear or radial. So when you needed to render tonal graduations in more elaborate shapes, you employed Blends.
More recently, programs have acquired a newer construct, which is an elaboration of grad fills: Mesh Grads. Mesh Grads are also mathematically-derived and remain as such up to print time--that is, they are vector. They offer more control over the shape of the color transitions. But that control is quite tedious, and is not at all like painting with an airbrush.
That's about the extent of it when it comes to maintaining "clean, vector edges". With skill and discernment, the results can look just as realistic as airbrush work, and it can be entirely vector. But the interface for doing it is not an emulation of painitng with an airbrush.
Far more common than a purely vector tool in a vector drawing program that tries to act like an airbrush is the workaround of applying filters or effects to vector paths. Doing that is not purely vector: It's actually rasterization that is re-applied whenever you edit the paths. If you set such an effect as the current default, then you can draw paths with the Brush tool, the Pencil Tool, or really, any of the vector path tools, and that's about as close to emulating an airbrush in a vector program as you'll get. The PDF mentioned above employs that kind of approach. But you should understand, you're really creating raster images when you do that. It's just that, rather than the raster images being "nailed down", they are effectively deleted and re-created on-the-fly if you edit the paths to which the effect is applied.
Illustrator isn't great at this. Other programs--Xara Xtreme in particular--do it much faster and responsively. But again, even though it retains the lossless editability advantage of vector art, the soft-edged effects are not really vector art. The are on-the-fly rasterizations of vector art.
Look up Blends, Grads, and Mesh Grad in Illustrator's Help files.
Wow. I will be deciphering this for a week. Thanks for the explanation.
Sent from my Verizon Wireless BlackBerry