Using Opacity Masks to Create Gradients on Gradients
Create gradient “swoops” that blend into other gradients.
Create the Base Artwork
One of the hardest effects to achieve in Illustrator has always been to create a gradient that intersects another gradient. Although this effect can easily be done in Photoshop using layer masks, the downside is that the artwork isn’t scalable because it’s raster-based. The problem with an Illustrator gradient is that it must have a “starting” color and an “ending” color. A gradient cannot start or end with a value of “no fill,” and consequently the gradient must blend into a solid background color. With the introduction of opacity masks this “blend on blend” is not only easy to achieve but very flexible too.
In this project we’ll create a series of solid colored “swoops” that overlap and interact with each other, and with background gradients and rendered spheres as well. But first we need to create the basic artwork including the “striped” planet and flying saucer (see Chapter 2, “Create 3D Planets”) A. For the “swoops” we’ll use two overlapping circles and Live Paint to give us the greatest flexibility. B
Create the Opacity Mask
Draw a rectangle on top of one of the swoops. Fill the rectangle with a simple black and white gradient A. Remember, although you can create an opacity mask with any color, it’s preferable to use black and white.
After making the gradient, select both the gradient and the swoop B, go to the Transparency palette and in the palette menu choose Make Opacity Mask C.
Tweak the Opacity Mask
In the Transparency palette either click or Option (Alt)-click the opacity mask thumbnail A to modify the gradient so that there is a nice transition from the lower left corner to 3/4 of the way toward the rocket ship B. Then create another gradient at the opposite end of the swoop to make it fade off at the end of the rocket C. When you’re done, click the artwork thumbnail D to go back to the regular artwork mode. The result should be a gradient that fades off on both ends to no fill while also showing the background planet gradients behind it E.
Repeat the preceding steps as many times as you like, and then position the swoops in front or in back of each other by changing the stacking order F.
Make the Rocket Engine Blast
Create the “blast” coming from the rocket’s engine with another opacity mask. Draw a circle and fill it with a Radial Gradient from white in the center to black at the outer edge A. Using the Free Transform tool or Selection tool bounding box, squeeze the circle so that the gradient “flattens” out a bit B. Now create a simple white rectangle and cut and paste in back of the gradient you just made. Select them both and create an opacity mask from the two objects C. The result is a graduated white “blast” that fades to nothing at the edges. All that’s left to do is to cut and paste the blast in back of the rocket and move it into position D.
Add the Final Touches
To complete the image, drop a gradient fill into the background, bring back the other artwork, and then add some final touches such as stars, spatial anomalies, and so on.