Game Development Reference
These two cameras, offset from the monocular camera, generate a left and right frus‐
tums. As you can see, there is a location where these two frustums intersect; this is called
the convergence distance . Objects that are placed at the convergence distance will have
the same appearance to both cameras. Note that the cameras are all pointed in the same
direction; this is called the off-axis method . This requires the frustums to be asymmetric,
which most modern graphics libraries support. Now, at first glance, it might be tempting
to toe-in the two frustums so that each camera's frustums are symmetrical, as shown in
Figure 24-4 .
Figure 24-4. Toe-in method (incorrect)
This will create workable stereopairs, but along with the horizontal parallax will intro‐
duce some vertical parallax. This can cause eyestrain to the viewer and should be avoi‐
ded. Instead, the off-axis technique should be used; it is illustrated in Figure 24-5 . One
of the objects is beyond the screen in the background, and one is in front of the screen.