Chapter VI

Stereo advanced rules: windows

In anaglyphs, and more generally in all stereo images, we find that they are not images but volumes.
Specific rules, which are not in use with flat images, have to be respected to display the volumes.

Unless you are standing alone with nothing more than the horizon and the sky around you, space appears relative to some frontiers.
This is what happens when you look through a window.
In the case of a stereo image displayed on a computer screen, the four physical sides of the screen (Left, right, up and down) are absolute frontiers.
They build a window through which you can see the stereo reconstructed space.
That introduces the following specific restriction:

That means that you cannot see in front of a window something that is too large to go through this window.
The spatial coherency has to be respected between the stereo scene and the screen that displays it.

Very often you will have to move your stereo image back into the screen.
If you don't do it, you will produce stereo images that viewers will not be able to fuse.
A typical reason is that points that normally should be at the infinity (Or at least far away) will lie just on the screen surface.
They will have quite no parallax.
This will make an aberrant springing stereo image, completely out from the screen.