Remember Magic Eye images? At first glance they appear to be a random pattern, but when you look at them a certain way, a 3d effect occurs and a separate image pops out and appears to float on top of the pattern. I saw one the other day and wondered if it might be possible to reproduce the effect in Photoshop.
Here's what you will be creating. It is a type of stereogram. For a quick intro on what stereograms are and how they work, view this link. Try this page if you need help seeing the 3d effect. See if you can find Pacman in this image:
Ready to move on? Let's see how it's done.
Create a new 600 x 250px image. Using the Rectangular Marquee Tool, draw a 150 x 250px selection starting from the left egde of your image. I like to use the Info window to help get the correct dimensions (press F8 to toggle the info window).
Go to "Edit > Fill" in the top menu, select Pattern. When the pattern swatches pop up, click the arrow in the upper-right corner and select "Patterns."
Select the Nebula pattern and click OK to fill your selection. Some patterns work better than others - this one is good because it has a lot of texture.
Add some noise to make the background more varied. Go to "Filter > Noise > Add Noise" and use the following settings:
Duplicate your background layer (ctrl+j) and move the new layer 150px to the right. You can do this by eye or hold shift then hit the right arrow key 15 times.
Repeat this process to fill the entire background. Merge all of your layers (ctrl+click each layer in the Layers window, then right-click and select "Merge Layers").
Draw a 140 x 140px selection with the Elliptical Marquee Tool approximately as shown. You don't have to use an exact size or line it up perfectly, but make sure it is less than 150px wide or your end result will be messed up. The white border is only there to show where the selection is.
Copy your selection (ctrl+c) and create a new layer from it (ctrl+j). Move the new layer 10px to the right (hold shift and press the right arrow key). You can now hopefully see your stereogram starting to materialize. You should be able to see a circle popping out near the center of the image and a circle to the left which is sunken in.
At this point I was stumped and couldn't figure out how to get rid of the sunken circle. I found a tutorial for Paint.NET that addresses this problem. Thanks to the author for this clever solution.
Duplicate your circle layer and move it 150px to the left. This will cover up the sunken circle perfectly, leaving you with just the circle popping out. And you have yourself a stereogram.
Once you get the basic idea, you can start experimenting with more advanced cutouts and multiple layers of depth. To create multiple cutouts, complete the tutorial, then merge all layers and use the merged layer as the background for the next cutout. Then repeat the process. For this image I added the 2 small circles and shifted them to the right 5px instead of 10, which makes them pop out less. Here's Pacman again:
You can still apply filters and adjustment layers to change the look of your image after it's done. Here's one with "Filter > Brush Strokes > Dark Strokes" applied:
It is also possible to make the cutouts have a 3d appearance (instead of just a flat shape popping out), but I haven't figured out how to control the results enough make a tutorial about it. Maybe someday...
More Tutorials: 
