The basics of opacity masks in Adobe Illustrator
Masking is an incredibly powerful tool for making textures and fades in the Creative Suite. Both Photoshop and Illustrator can create these effects, but there are pros and cons to using each. Making textures in Photoshop can often become cumbersome and tedious, due to both the interface and the nature of its graphics. In Illustrator however, textures are a breeze to make and edit, as well as being highly flexible vector graphics. In this tutorial I will show you how to use opacity masks in illustrator to create textured effects with ease.
First, a little bit of theory
Opacity masks are simple. Basically you have an object or layer, and a mask is applied on top, allowing layers below to show through. Masks are made of black, white or shades between (colors work too, but I would not advise it). By default, the black part of a mask will show through, and white will not, but this can be changed to suit different situations. Often I like to invert the mask, making my texture black, as you will see. Shades of gray lower the opacity of the object below in correspondence with the amount of black (ex. K=20 means 20% opacity). With these basic principles in mind, three patterns of mask emerge.
The first pattern is of a solid black or white texture applied over the object, as seen on the left in the example below. The second is of multiple textures with different shades of gray, creating multiple colors in the object. The last is of a gradient, which creates a fade.
Putting said theory into practice
Open a new document, whatever size you like, and paste your vector object and the texture into the art board. You should adjust the size of the texture depending on how you would like to overlay it on the object. In my case I’ve made it about the same size, so it will fill the shape nicely, while still allowing the texture to show. The size and appearance of the texture is up to you, so go wild, but remember to use black, white or gray. Here I’m using on of my scribble textures from the Life Under Glass Vector Pack. The icon is the Creative Commons Icon, available here.
Select your texture and cut it from the art board, cmd+x or ctrl+x. Now select your object and double click on the empty window in the transparency palette. If you don’t see the window, make sure all of the options are displayed by clicking the drop-down in the top-right corner. The left window is the object, and the right window is the mask, just like in Photoshop.
You will also need to make sure that “Clip” has been checked. As a personal preference, I like to keep my textures filled with black before pasting, so I invert the opacity mask to make black the opaque part of my object. If I did not invert the opacity mask, my shape would still be invisible, unless I switched the texture’s fill to white. Either way works the same, so choose whichever you like best.
You may think your object has disappeared, but it has not. Paste your texture back into the artboard and move it over where the object was before. In the example below my texture is filled with black; gray would work too, but not white because my mask is inverted.
When you are done positioning the mask object, deselect it to see how the object looks, and then click back on the left window of the transparency palette. Now you have an object with texture. The best part is that you can easily change the fill or stroke, or even use some effects, and the same mask applies. If you want to edit the mask again, all you have to do is click the mask window.
There you have it, a textured vector object that’s easy to edit and change with only a few clicks. Because this is vector art, you can pull it into any of the Creative Suite applications without worrying about image loss. In the download you will find my original Ai file, complete with all the vectors used in the tutorial. As an added bonus, I’m including my new hand-drawn stamp vector. If you have any questions, or I have been unclear, please leave a comment.