Stereoscopic Vision
Each eye gets a slightly different view of the world
The brain fuses the two views to get depth information
Artificial Stereo
Create two distinct images - one for each eye
Used since early 1800s
Stereoscopy
Stereoscopy
Stereoscopy
Stereoscopy
Stereoscopy
Stereo Viewing
Present each image separately to each eye
e.g. stereoscope, HMD
Stereo Viewing
With a projection screen, images must overlap
Glasses filter images - each eye sees only one
Crosstalk becomes a concern
Active Stereo
- Shutter glasses with liquid crystal lenses
- One lens clear, one lens dark at any time
- Left- / right-eye images displayed alternately
(by single projector)
- Glasses synchronize with video
Active Stereo
Problems:
- Glasses are expensive
- Glasses are relatively fragile
- Requires high video frequency to prevent flicker
- LCD projectors not capable of high frequencies
- Affordable DLP projectors don't support high frequencies
Passive Stereo
Uses polarization to separate images
Two projectors - one for each eye
Each eye's image is polarized differently
Linear Polarization
Linear Polarization
Problems:
- Tilting one's head diminishes stereo
- Screen must preserve polarization
- LCD projectors polarize light
- Mirrors can affect polarization
Circular Polarization
Linear polarizer + quarter-wave retarder = circular polarization
Polarization is left-handed or right-handed
(clockwise or counter-clockwise)
Immune to head-tilt problem
Circular Polarization
VR Screen
Circular Polarization
Problems:
- Filters & glasses harder to find
- Moderately more expensive
- Glasses cannot be flipped
- Same screen, projector, & mirror problems as linear
Other Methods
- Anaglyphic
- Chromadepth
- Pulfrich effect
- Autostereo
Anaglyphic Stereo
Uses colored filters
One image is red, other is blue/green/cyan
Only requires one projector (any type)
Anaglyphic Stereo
Anaglyphic Stereo
Chromadepth
Filters make different colors appear at different depths
Red appears close, blue appears distant
Chromatek gallery
Pulfrich effect
Images viewed through dark lens reach brain slower
Pulfrich glasses have one dark lens, one clear lens
When objects move, brain fuses images from slightly different times
Autostereo
Glasses-free
Different eye-views are interleaved vertical strips
Barrier screen blocks all but one image from any viewpoint
or lenticular lenses direct a different image to each eye
Stereo in OpenGL
Display
- Active stereo
- Quad-buffering: glDrawBuffer() etc + special hardware
- Polarized stereo
- One display: Quad-buffering + polarizing modulator
- Two projectors: glViewport()
- Anaglyph
- glColorMask()
Perspective
- gluPerspective() + glTranslate()
- glFrustum() + glTranslate()
glFrustum
glFrustum
glFrustum
glFrustum
This document is by Dave Pape, and is released under a Creative Commons License.