Adobe Illustrator’s Blend Tool

Was a time, Uncle Luc used a lot of blending in his work. The Blend Tool, in Adobe Illustrator, is something that allows you to create complex gradient effects by blending (duh) one shape into another. It can be used to suggest shading, highlights, movement, and thus dimension.

I don’t use it much anymore; I’ve been making efforts in the past two years to simplify my work as much as possible, and the use gradients and blends often runs counter to that desire for simplicity. I find many illustrators (me included) have used them as crutches sometimes; solving a complex visual problem with a fancy digital effect.

But when I did use them a lot, I posted a how-to on my site, which got linked to A LOT. Eventually I took it down, but I still get requests for it to this day. I didn’t have a copy on my computer nor my server, but I was able to find a cached copy using Archive.org’s Wayback Machine (the whole thing was intact, save one of the JPGs, which I’ve replaced). The info may be a tad out of date (this was written when I was using a copy of Illustrator 8.0, and on a PC) but the basic idea is the same. Click below to read the whole thing, unedited. (Speaking of which, if you find errors or omissions, please let me know, and I’ll correct it toot sweet.)

Using the Blend Tool in Adobe Illustrator

I started using this feature a few months back and have experimented quite a lot with it with very nice results. I had always ignored it before because it didn’t seem terribly useful or impressive. Basically, it does exactly what it says it does: It blends two separate elements together. Period.

This can look really cool if you know what you’re doing. Or it can look so crappy and useless that you never bother using it again and wonder what the heck Adobe was thinking. 

The end result, depending on what effect you’re trying to achieve, can look like a blurred or airbrushed shape, almost as if you’ve created it in Photoshop, except it doesn’t eat up nearly as much memory, and you don’t need to rasterize any of your artwork. It also remains editable, which we all like.

It may also reduce the number of times you need to create bitmap elements in Photoshop and then import them into your Illustrator document, by allowing you to create it all in Illustrator.

(fig. A)

…or it can almost look like animation inbetweens (which might be useful for creating those inbetweens for later use in Flash):

(fig. B)

In (fig. B), I’ve high-lighted the selected paths of the objects themselves and of the little invisible path that indicates the blend between the two, and I’ve also coloured the objects differently so you can see the progression made from one to the next. It not only blends the shapes, but colours as well.

Why does the one on the far right look all warped and hideous, you ask? Because the paths were too twisted and extreme to blend smoothly. There are two ways to fix this. You could try simplifying the two objects, which might not be a good option if it ends up changing the look of your illustration.

You could try reversing the start and end points of one of the two images. I have found that for line-blends, like these above, that trick almost always works. I don’t know why.

A third option is to try blending three objects. Add a third line between the two you drew (you’ll have to approximate what it would look like), then blend the first with the new line you just added. Now select the line you just added along with the final line, and blend those two as well. The three lines will be joined as one grouped object, and you can fiddle around with it to create the look you need.

There’s another way to smooth out your blends. You can add anchor points to the shapes to blend. Look at this example below (FIG. 1a, and FIG. 1b, which show both adding a third shape, and adding anchor points) and you can see differences in each one:

(FIG. 1a)

Here it is again, but with the paths selected so you can see how many anchor points were added:

(FIG. 1b)

Now, look at the two blended lines on the left in (fig. B) again:

You’ll see that, while the blended objects are the same, the blend itself is different. You’ll notice that I curved the invisible “blend-line” between the two. I did this using the pen’s “Convert Direction Point Tool” (if you select the pen’s sub-menu, it’s the little upside-down “V” on the far-right end):

Experiment with that. You’ll see that if you only curve one end of the path, the blends will bunch up at that end. If you curve both ends evenly, the blends even out as well.

Now back to (fig. A):

(fig. A)

I’ve created a purple blob using the pencil tool (N), copied it (CTRL+C), pasted it exactly in front of the original so they’re both perfectly aligned to one another (CTRL+SHIFT+F), shrunk it down, coloured it yellow, and blended it with a “4 step” blend (you know it’s four steps, because you can see four separate shapes between the purple and yellow ones; more on that below).

Then I had an iced tea, because that was hard work.

Now, the top ones are kind of pretty, even and smooth… But what’s up with the bottom one?! It’s butt-ugly!

That’s because I tried blending two very different shapes, with varying numbers and shapes of path-points. The two top ones are blends made of two identical shapes, even though in the second example on the right, they’re not aligned together. If you want your blends to work, you have to try to remember to keep the two shapes fairly similar.

I’ve noticed that even when I think my two shapes are similar, they may actually be made of different numbers of path points because I created them separately. This causes the blend to look very different than what I’d intended or hoped. I find the best way to achieve a smooth blend between two objects is to paste a copy of the first object on top, and shrink it to the size you need. That way, you’re blending identical objects, and most likely will get the effect you’re after.

(fig. C — Click to see a larger version of it in a new window)

I managed to achieve a somewhat smooth airbrushed or watercolour effect on the clear green plastic case through the use of several simple blends. I’ve isolated two of the blends above. I’ve dissected the gradient elements (yes, the blend tool does a fine job of blending gradients, too) and exaggerated the colouring on them so you can see the blend. The blends were composed of about 40 steps, not just 4 like you see above. Again, that’s just so you can see what I did. 

“Hey! How to I blend stuff?!” you ask. I usually use keyboard shortcuts while working, so I select the two objects I want to blend and then click CTRL+ALT+B (or whatever on a MAC), but you can do it through the main menu too. You can set the options of the blend by selecting “Blend Options” first, or double-clicking on the blend tool in the tool bar:

…or this:

(fig. D)

You can always change the blend options by selecting the object and typing in different settings. I won’t go into too much detail about it, but I usually I choose “Specified Steps” for “Spacing”, and set a number in the box next to it to create the exact number of blended objects between the originals.

The actual number I type in will depend on how large the object is, but I usually type in 24 or 36, and that’s enough. If you make more objects than that, the file becomes larger and more memory intensive of course. Too few, and the blend will look choppy and just plain yucky.

That’s not the end, though. To prevent potential problems with my clients’ printers, I “expand” the blends in an illustration when I’m finished and like how everything looks. You do this by selecting the blends (you can do them individually or all at once) and again going into the Blends sub-menu, and selecting “Expand.”

This converts the blend into several individual objects, grouped together (fig. F) and prevents any printing problems your client might have after delivering the final (I know the Gradient Mesh Tool can create major problems if the printer doesn’t have the drivers or whatever to support this feature; I once used the Gradient Mesh feature on some objects for a promotional postcard, and the objects turned out solid grey, no gradient, no colour… I don’t want to repeat that!).

(fig. E)

The illustration of the PowerBar above (fig. E) makes extensive use of blending (not to mention masks, gradients, and pattern fills) to help give the wrapper a 3-dimensional feel, and to add a shadow against the white background. Let’s look at it more closely (sorry for the choppy-looking JPG):

(fig. F)

This also shows you the “Blend Options” palette I mentioned earlier. Well, that’s pretty much it. If you still have questions, refer to the Help file in Illustrator’s menu, or to your manual, or just experiment on a tmeporary file and see what you can discover by yourself. Because I’m done here!

cheers,
Luc