Game Development Reference
In-Depth Information
Figure 24-5. Off-axis method (correct)
You can see that if you wish to move something to greater than screen depth, the object
must be shown farther to the left than if it were at screen depth for the left eye image.
For the right eye image, the object must be shown farther to the right. If you want to
show something coming out of the screen, the opposite is true. The left eye will see the
object as farther to the right than if it were at screen depth. Also note that each object
will have a slightly different angle as well. Again, the distance between the right eye
image placement and the left eye image placement is referred to as parallax. The amount
and relative orientation of parallax is the chief way your brain creates 3D images. In
fact, the most important aspect of the physics of stereoscopic display for programmers
to understand is that there is a parallax budget that they must use wisely in developing
programs that take advantage of 3D display. This budget defines the ranges of parallax
that your viewer's brain will be able to accept comfortably. We'll discuss this in detail at
the end of the chapter.
For now, we'll consider that if we were to just show the right and left images on a screen
without further work, you'd end up seeing two images with both eyes and no 3D effect
would be produced. It is paramount that the image intended for the left eye is seen only
by the left eye and vice versa. These two channels, the left and right eye, must be kept
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