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As always, we will be using Pixels as our units of measure. Right click on the screen and select Page Options... from the pop up menu. In the Units tabbed section, select Pixels for the Units and 0-255 for the Color Units. In the Grid and Ruler tabbed section set the Major Spacing to 100pix (key it in exactly like this please) and the Number of Subdivisions to 10. Press OK to close the dialog and apply the changes.

NOTE: You will notice from time to time I apply arbitrary colors to objects. I do this to make the objects easier to see. If I do not specify a fill for an object, you do not have to apply a fill or outline color.

When I show an ellipse or rectangle that has just been created, that has no fill, it is because I have set the fill to none before I exported the illustration. By default, all ellipses, rectangles and Quick Shapes have a black outline and a black fill. There is nothing wrong with your copy of Xara.

Naming Conventions. I use bold face to indicate the names of tools, galleries, keyboard shortcuts, and dialogs. Items such as unnamed icons and drop down lists, which have names when you let your cursor rest over them for a moment, are displayed in italics. Enough small talk, let's get on with the tutorial.

Stereograms are images that appear to be nothing more than a random assortment of dots or patterns as shown above. However hidden inside the random dot pattern is a 3D image that when you stare at the Stereogram for a little while, appears. The most common type of Stereogram is called a SIRD (single image random dots). All but the image above in the lower right corner are SIRDS. The image in the lower right is called a Color Field, Wallpaper, or repeating panel Stereogram which is what we will create in this tutorial..

Stereograms use what is called a Depth Field image to determine the shape of the hidden 3D image. The Depth Field image uses 256 shades of gray to determine depth. White comes forward while black goes to the back. The other 254 shades of gray represent the steps in between.

The Depth Field image (the circle and rectangle) produces a very distorted sphere, almost a cone shape, as it incorporates all 256 shades of gray. It is placed over a rectangle that is 50% black right in the middle of the sphere. The Stereogram created with this image is of a circular hole in the background with part of the sphere in front of the rectangle and part of it behind the rectangle.

Color Field stereograms (also called repeating panel or wallpaper) use a repeating panel in which to hide the image as shown in the example above. If you look at the Stereogram on the bottom carefully, you will see that the pattern repeats about 6 times. While each panel appears the same, in fact they are not. Subtle shifts in the pattern are what the eye and brain reassemble as the hidden 3D object. In the Stereogram above half of the sphere (cone) is in front of the background and half appears receding behind the rectangle. This is the kind of Stereogram we will create in this tutorial.

We will use Xara to create the Depth Image and the Colorfield panel. We will use a freeware program called GP PopOut to create the Stereogram using the images we provide. GP PopOut is a simple and easy to use application. I will explain how it works when we come to that part of the tutorial.

Click here to download GP PopOut (298K).

GP PopOut is an old application that was written for Windows 3.1 (which tells you how old it is). It works fine with all versions of Windows although the limit of 8 characters to a file name brings back unpleasant memories.

Instructions: Create a Directory on your hard drive and call it PopOut. Extract this Zipped file to that directory. Double click on Popout.exe to launch the application.

Here is a website that Dale Landry brought to my attention that has a lot of technical information about how stereograms work and how to view them. www.cs.waikato.ac.nz/~singlis/sirds/general.html The design of the page suggests it was designed about the same time as GP PopOut!

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