Stereograms, also known as autostereograms, are optical illusions that depict an image within a picture that can be viewed while crossing your eyes. While staring at the 2D stereogram, you can detect a hidden image that will appear as a 3D object. Although a well-crafted stereogram takes time to accomplish, there has been an influx of graphic rendering software applications that make designing graphics such as stereograms easy. Find an autostereogram to practice viewing. If you can’t find one readily available, you can find stereograms to view for free at www.eyetricks.com/3dstereo.htm. As you look at the image, gently begin to cross your eyes inward, which will cause the single image to appear as two images overlapping each other. Continue to view the image for approximately ten seconds in this manner, gently adjusting your eyes’ focal points, until you begin to see a shape appear in the background; this is why many people call it “looking past the picture.” Continue to fine tune your focus until your brain registers the 3D image. Open your word processor. Use whatever software you’re most familiar with, but the most basic word processing application will work. At the top of your image, type two asterisks ten spaces apart. You may need to return later and fine tune this, depending on the size of your image. Press ‘Enter’ to skip ahead a few lines and then type any character, such as the letter ‘X’. Type the X and then move ahead a number of spaces in the line and type another X. Type as many Xs as you can in this manner, spacing each X evenly, until you reach the right margin. Skip ahead another few lines and type a new character, such as the letter ‘Y.’ Fill the line with evenly-spaced Ys in the same manner that you completed the line of Xs, but increase or decrease the Y spacing as compared to the X spacing by at least two spaces. If there are ten spaces between Xs, you can put eight spaces between Ys. If you want, you can print this image, but you will be able to view the stereogram properly using your computer. Allow your focal points to diverge, crossing your eyes slowly until two of the asterisk doubles converge, creating the appearance of three total asterisks. As the letters begin to converge, the Ys will appear to be on a higher level than the Xs. If the stereogram was unsuccessful, go ahead and tweak your image to get the desired effect. Using this technique, you can experiment with advanced stereogram displays to create a more complex perception of 3D depth. GIMP, or GNU Image Manipulation Program is another software application available under the GNU General Public License. GIMP can be used to create the texture necessary to hide the 3D rendering created in Blender. A simple texture can be created by selecting the ‘Tools’ menu from the top margin, and then selecting ‘Fill’ to bring up an option menu of different texture patterns. A ‘Pattern Fill’ option available in the ‘Tool Options’ dialog box will expand the texture to fill the entire background. This texture can be saved as a *.png file, where the asterisk is any given filename. These .tga and .png files can be compiled into a stereogram by using stereogram generating software. Stereogram Maker is a free program available for download through a number of Internet download portals, such as freewareapp.com. Stereogram Explorer is another program that will create stereograms from .tga and .png files, and a free trial is available at www.aolej.com/stereo. When looking for software, make sure to choose a download that is compatible with both .tga and .png files. These stereogram generators contain the proper algorithms for superimposing the .tga image into the .png textured background. This process will differ based on the software you choose.
