Contributed by Brenda Sutherland, Illustrator Team Rowing Captain
I know we’ve all had this experience. You take on a project that looks so simple you’re confident you’ll knock it out in no time. Then it turns out to be far more complicated then you ever expected, and you realize that to do it well is going to take a lot more time and effort. That’s exactly what happened when we implemented the Blob Brush in CS4. We thought it would be a pretty simple thing to do, as we had already implemented the Eraser tool back in CS3, and the idea behind the Blob Brush was to use Pathfinder to create shapes like the Eraser does, but instead of erasing them, fill them with color. What could be simpler than that?
I suppose if we had left it at that, it just might have been that simple, but there was another piece that seemed essential to making this tool complete, and that was merging. If you’ve been following my series on Pathfinder and the features in Illustrator that use the Pathfinder Engine, then you’ll recognize the connection here. The Blob Brush works in a very similar way to the Eraser tool in that is starts off by creating a Calligraphic Brush object, expands it into simple paths, then runs Pathfinder to create either a simple or compound path, eliminating all the overlapping brush strokes as well as the original path.
Because it starts out as a Calligraphic Brush object, it has all of the same functionality available that Calligraphic brushes have. If you are using a pressure sensitive tablet, you can even vary its settings just as you can with a brush. And like the Brush and Eraser tools, you can increase and decrease the size with the square bracket keys.
So one question you might have is, if the Blob Brush is so similar to the Calligraphic Brush, why did we go through all this trouble to create a new tool in the first place? The answer is that as cool as brushes in Illustrator are, there are times when all you want to do is create a simple path, a blob so to speak, that doesn’t have editable brush attributes after it’s been created, but can easily be erased, have gradients or live effects applied, and if it’s not the right shape, can be added on to without having to expand and then run pathfinder on.