Ken Wittlief, a senior engineer at Vuzix (formerly Icuiti Corp), “makers of VideoEyewear and other micro display systems”, has written an excellent article about do’s and don’ts when creating a stereoscopic entertainment. Here are some highlights of the article, but I highly recommend you to read it all :
(…) our depth perception is only good out to approximately 200 yards. Beyond that distance everything appears to be flat, and we use sideways motion to judge distances. (…)
The first rule of getting it right: you have to know how the images will be viewed. You are creating a virtual space in front of the viewer and you must know what that space is, before you can start placing shapes and objects at different distances. The reward for your attention to this detail is that it is possible to create images that will appear to exist in real space, across the front of the theater, extending halfway out the screen towards the viewer, and receding back for 200 yards or more.
(…) Focus is an issue with no easy solution. The best we can do with existing systems is to not violate the convergence/focus lock the viewers eyes have learned over their lifetime too harshly. [Don’t] push objects off the screen more than half the distance to the viewer (…).
(…) The average person has an Inter Pupil Distance (IPD) of 2.5 inches. (…) limit the separation on the screen to the minimum IPD that might be present in the audience: around 2 inches.
(…) The second rule for getting it right: don’t turn the audience into giants! You must use the correct camera separation for the camera field of view. For animation this means that first you must put your viewer into the virtual space itself. If you are animating bugs then how tall is your viewer? Do you want it to feel like the person watching the film is 6 feet tall, looking at bugs on the ground? Or do you want to bring your viewer down to bug size, so his eyes (your cameras) are the same distance apart as the bugs eyes?
(…) The third rule for getting it right: set your cameras to converge on the most distant objects in view, and adjust your separation so that infinity is 2 inches apart at the screen, and let the foreground objects find their own place in that space. Resist the temptation to converge your cameras on the center of attention. If you really want to lock the viewers attention on one area, then use a depth of focus effect to blur the rest of the image, so the viewer will not be inclined to look around the area at other things.
(…) The fourth rule for getting it right: you must know the timing of the projection system. (…) But when objects move quickly there comes a point when your brain sees the left view in one place, and the right view in another place, but then the left view has moved considerably and your brain cannot pull them together. The result is you see two objects: the stereoscopic 3D effect is lost.