COMS W4172 Perception, Displays, and Devices 3

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1 COMS W4172 Perception, Displays, and Devices 3 Steven Feiner Department of Computer Science Columbia University New York, NY February 20, What s wrong with these pictures? 2

2 Spatial multiplexing VR: Stereoscopic viewer for smartphone/tablet AR: Separate left/right stereoscopic views of virtual objects combined with shifted copies of a monoscopic camera view Commercial versions (w/o camera support): vr.google.com/daydream/ Stereo viewer used with Goblin XNA and Nokia Lumia Google Cardboard Stereo viewer for Nokia Lumia 800 courtesy of USC ICT MxR Lab Build your own: 3 Autostereoscopic Viewing Spatial multiplexing Parallax barrier approaches Parallax stereogram (F. Ives, 1901) Viewer s eyes need to be positioned properly 4

3 Autostereoscopic Viewing R L R L R L Spatial multiplexing Parallax barrier approaches Parallax panoramagram (C. Kanolt, 1915) Presents different stereo pairs at different locations Can use physically moving mechanical or virtually moving liquid crystal barrier to create active display for tracked user mrl.nyu.edu/~perlin/demos/autostereo.html Y B Y G 5 Autostereoscopic Viewing Spatial multiplexing Lenticular approach (H. Ives, 1930) Array of cylindrical lenses Brighter than barrier Note: Refraction not modeled properly in figure! 6

4 Autostereoscopic Viewing Reconfigurable from mono to stereo Goal: Display that can switch from autostereoscopic 3D to 2D Solution: Parallax barrier made from switching LC panel that can be turned on or off HTC Evo 3D Nintendo 3DS Was used in SHARP 3D desktop displays and laptops 7 Red cyan (earlier red-blue ) anaglyph stereo Display overlapped left/right images in red/cyan Can create by Combining red channel of left image with green/blue channels of right image Converting left (right) image to greyscale and displaying as red (cyan) 8

5 ColorCode 3-D Display overlapped left/right images in amber/blue Left eye provides color (mostly) Right eye provides second eye s geometry (mostly) Better color rendition than red/cyan anaglyph Imagery looks better without eyewear Other color pairs used by other vendors 9 Infitec Display overlapped left/right images using different RGB primaries for each eye Special narrow bandpass filters used on projector and in eyewear eyewear (expensive) Metallized screen not needed Very low crosstalk Slight L R color shift

6 (single image) Chromostereoscopy Different colors focus at slightly different points on retina (red closer to temple than blue for most people) Caused by chromatic aberration Perceived fused depth (blue) Perceived fused depth (red) Left eye seen from above Actual position of object (black) and optically shifted positions due to red and blue focusing at different offsets on retina. Exaggerated! Optical axis Fovea is off center relative to eye s optical axis. Index of refraction varies with wavelength (red < blue) 11 (single image) ChromaDepth TM stereo Inspired by chromostereoscopy Refractive/diffractive optics over right eye shift colors differentially to the left (red > blue) Actual position (black) and optically shifted positions Perceived fused depth (blue) Perceived fused depth (red) Exaggerated! Optics Effect is more extreme if optics are used for both eyes 12

7 (single moving image) Intensity multiplexing Pulfrich effect Dark filter over one eye causes perceptual delay Note: Moving images only (e.g., Dark filter on eye at leading edge of horizontal motion brings it forward Perceived depth Left right motion Optics Actual position (black) and perceived position (grey) Perceived depth Right left motion Optics Actual position (black) and perceived position (grey) 13 Polarization state multiplexing Linear (horizontal/vertical) Circular (lefthanded/right-handed) Polarized light has the tip of the electric field vector following a particular path 14

8 Polarization state multiplexing Linear (horizontal/vertical) Circular (lefthanded/right-handed) Linearly polarized Circularly polarized 15 Polarization state multiplexing Linear (horizontal/vertical) Circular (lefthanded/right-handed) Robust to head roll Screen must preserve polarization (metallized) Linearly polarized Circularly polarized 19

9 Stereo Content Caveats Geometry Avoid window violations: Objects at screen edges that extend in front of the screen and are cut off by the edge Avoid extreme parallax Avoid rapid/discontinuous changes in depth over time Color coding for anaglyph Avoiding objects whose light is sent to only a single eye after filtration (e.g., red or blue objects) Some anaglyph approaches ( allow slight leakage of red into the cyan filter to support redness cues in both eyes Image with front of landscape protruding from screen, violating window edges (NASA Mars Pathfinder) Image after shifting L and R views horizontally (and cropping out edge portions with only one view) to adjust front of landscape to be behind screen 20 Active Temporal multiplexing Liquid crystal shutter eyewear Right/left lenses alternatively opacify in synchrony with display of left/right views L R L R Synchronized to wireless (e.g., infrared, Bluetooth) emitter CrystalEyes LC shutter eyewear 21