Perspective Projection - Transformations and Projections in Computer Graphics - page 128

Figure 3.48: Stereoscopes.
RLL
At this point, your right eye sees the right image and your left eye sees the left image.
Try to ignore them and concentrate on the central image. When you are successful, the
center image will feature depth; it will be stereoscopic.
If you are one of those who find this technique di cult in practice, try the following
aid.
R
L
Place a finger here
1. Observe the image above with the R and L targets.
2. Place a finger on the paper, right under the two targets, as indicated.
3. Stare at your fingertip and, while still looking at it, slowly move your finger
away from the image pair and toward your eyes.