Normal human vision gives us the ability to perceive scenes and objects with depth, so that we know whether parts of a scene are nearer or farther away than other parts. We use many cues to help our sense of depth perception, but one of the most important is our "stereoscopic vision." Each of our eyes views a scene from a slightly different angle. Each eye sends its own image to the brain, which the brain then combines into a single, three-dimensional scene.
In principle, generating stereo 3D is quite simple: since we humans perceive depth using two eyes spaced about two inches apart, all we have to do is display a different image to each eye containing the correct cues for depth perception, and then the brain can fuse the two images into one and will perceive that it is, indeed, looking at a 3D object or scene.
There are at least three ways to achieve this separation and channeling of information to the proper eye:
- Anaglyph - using colored images (normally red and blue) and filters worn over the eyes.
- Polarized - using vertically and horizontally polarized images with corresponding polarizing filters worn over the eyes, projected onto a screen that maintains reflected polarity of the images.
- LCD shutters - Special eyeglasses consisting of LCD shutters controlled in sync with the presentation allow each eye to view the proper image at the proper time.
There are both advantages and drawbacks to each method. These are:
- Anaglyph -
- Advantages: any full color projector equipped with 3D software should be able to produce this, and the glasses are inexpensive.
- Drawbacks: Color information lost.
- Polarized -
- Advantages: inexpensive glasses, images retain their full colors.
- Drawbacks: Special screen required; extra hardware to provide another image at opposite polarity required; some "bleedthrough" of images between eyes is inevitable.
- LCD Shutters -
- Advantages: perfect separation of images with full color.
- Drawbacks - Complex and relatively expensive eyewear required for each viewer, along with software and hardware to drive eyewear in sync with projections.
For programming, software is necessary that allows two views of the same object or frame to be presented at one time. The object must be located in a virtual 3 dimensional world and the two views should correspond to the views that left and right eyes would see. The software must allow these two views to be specified along with the distance between the eyes and the distance to the projection screen.
Fortunately, on the Lasergraph DSP, stereoscopic 3D is "built in." Every DSP is ready to control an XY-RGB scanner head normally, and by adding two simple commands at the beginning of your film script, the film will be projected in anaglyph 3D. You even have parameters to adjust the ratio of red to blue/green colors in each eye, so that the original color information in the pictures is not totally lost. With red/blue or red/green glasses, you can enjoy stereoscopic 3D right out of the box.
