Stereogram Autostereogram Tutorial – by Ego Eram Reputo 29 March 2009
This tutorial is available as a free PDF. Click here to open or download the PDF
Warning, this tutorial assumes:
1. You know how to MOVE an entire layer by a number of pixels left or right
2. You have installed & can use WEAVE and DENTS (not absolutely essential if you can create some other nice pattern for the background)
3. You can DUPLICATE , RENAME and MERGE layers
4. You know how to view a stereogram image
What is a stereogram/autostereogram?
An (auto)stereogram is an image which contains a hidden 3D image within it. Viewing the image in a certain way tricks the eyes into seeing the 3D image which appears to “pop out” of the original image. For more information: Stereogram (Wiki this) and/or Autostereogram (Wiki this)
How do I view an (auto)stereogram?
There are several ways to view the image in order to see the 3D image within. For more information: http://en.wikipedia.org/wiki/Autostereogram#Mechanisms_for_viewing
Your background needs to be a pattern that repeats across the horizontal width of the image. Preferably the pattern should repeat four or more times across the width. In this tutorial I’m going to call the width of the repeating pattern (in pixels) the Phase. The phase determines the maximum width of an element that you can have “floating” in the foreground over the background. So you cannot have a floating element that is wider than the phase (well actually you can, but that is beyond this simple tutorial).
If your floating image is say, text, make sure that each character is no wider than the width of the background phase.
Here’s the background we’ll be using in this tutorial, (530 x 142 pixels)
1.Weave @ size 10 & 25 degrees
2.Dents @ Scale:156, Amount:16 & Quality:2
Now we make the background repeat across the horizontal width. To do this we are going to tile a strip 128 pixels wide across the width of the image. Here’s how:
3. Duplicate the layer
4. Select the top layer and move it to the right by 128 pixels (128 is our Phase = P).
5. Duplicate the top layer
6. Select the new top layer and move it right by 128 pixels
7. Repeat the duplication & moving steps (5 & 6) until the whole image has been tiled left to right in 128 pixel wide strips.
8. Merge all the layers from the top down into a single layer
9. Name this layer “Background”
Now we need something to “float” over our background (“They all float down here” – Pennywise ). For this simple example I’m going to use the characters ABC.
10. Add a new layer & rename it “Text”.
11. Select the text tool and a fairly large font and type the characters in black onto this new layer. Pick a font that is fairly thick and also a reasonable size. I’m using a font named Plump MT @ about 90px. Position the text slightly left of centre. Remember, the width of a letter should not exceed the image phase.
12. Select the letter C with the wand (Shift+S selects the wand tool then click on the letter C).
13. Invert the selection with Ctrl+I.
14. Duplicate the background layer and select the top of these two identical layers.
15. Rename this layer “Right-C”
16. Press delete to remove the previously defined selection.
17. Select the Move tool and move the Right-C layer to the right by 6 pixels. 6 pixels is an amount that can be varied later when you get familiar with this technique. Smaller shifts (say 3 or 4 pixels) will make your floating foreground elements appear nearer the background. 10 pixels would make the foreground appear further away from the background. Stick with 6 pixels for the duration of this tutorial.
Now your stereogram will actually work. Turn off the visibility of the TEXT layer and view your stereogram with parallel eyes (tip: focus on the wall behind your monitor, or alternatively, focus on your reflection in the monitor surface). Keep at it until you can see the C floating above the background.
But wait! There’s something wrong, right? :? Yep, there is a funny “inverted” C to the left of the floating foreground one. It should look like it’s sunken into, or is behind the background. Well spotted ? The technique I use to remove these artifacts is called “Backfilling”.
18. Duplicate the Right-C layer.
19. Rename the lower of the two identical layers “Left-C x 1”
20. Select the Left-C x 1 layer
21. Move this layer left by the same number of pixels as the phase. In this case 128 pixels to the left.
All done? Good, try viewing the image again.
There still may be an artifact visible to the left, but further left that it was before. We need to backfill again, by another 128 pixels. So….,
22. Duplicate the Left-C x1 layer.
23. Select the bottom of these two identical layers.
24. Rename this layer “Left-C x 2”.
25. Move this layer to the left by 128 pixels (one phase).
That should take care of the last artifact. View your image to make sure all the sunken in artifacts are really gone.
That’s just so cool isn’t it?
You can now merge the Right-C layer and all the Left-C layers together.
26. Select the Right-C layer and keep merging down until you have only the Text and Background layers remaining.
Time for a B
Now you need to repeat the right shift for the character B.
27. Make the text layer visible, and select that layer.
28. Select the letter B with the wand (Shift+S selects the wand tool then click on the letter .
29. Invert the selection with Ctrl+I.
30. Duplicate the background layer and select the top of these two identical layers.
31. Rename this layer “Right-B”
32. Press delete to remove the previously defined selection.
33. Select the Move tool and move the Right-B layer to the right by 6 pixels
34. Backfill the artifact B that appears in the image by first duplicating the Right-B layer
35. Rename the lower of the two identical layers “Left-B x 1”
36. Select the Left-B x 1 layer
37. Move this layer left by the same number of pixels as the phase (128 for this tutorial image).
38. If you’re really unlucky, you may have to backfill once more (creating and moving a layer called “Left-B x 2” in exactly the same way you did for the “Left-C x 2” layer [steps 22 to 25]).
39. Select the Right-B layer and keep merging down until you have only the Text and Background layers remaining.
Now you should have a floating stereogram image of a B and C.
Lastly, A Time
40. Make the text layer visible
41. Select the letter A with the wand (Shift+S selects the wand tool then click on the letter A).
42. Invert the selection with Ctrl+I.
43. Duplicate the background layer
44. Select the top of these two identical layers.
45. Rename this layer “Right-A”
46. Press delete to remove the previously defined selection.
47. Select the Move tool and move the Right-A layer to the right by 6 pixels
48. Backfill the artifact A that appears in the image by first duplicating the Right-A layer
49. Next rename the lower of the two identical layers “Left-A x 1”
50. Select the Left-A x 1 layer
51. Move this layer left by the same number of pixels as the phase. In this case 128 pixels to the left. As A is the left most letter, you shouldn’t need to backfill it. But check by viewing the stereo image just to be sure. If you do have an artifact, repeat the backfilling technique [steps 22 to 25 but for the letter A this time ]
52. Select the Right-A layer and keep merging down until you have only the Text and Background layers remaining.
53. Deselect the Text layer visibility.
54. Save the finished image!
How uber-cool is that?
Notes for the Wicked:
1. You can vary the depth of the letters by one or two pixels to make them appear at different depths from each other.
2. Don’t feel that your background has to be colorless either:
Wicked or what?