Stereoscopic Imaging

Stereo Terms

• Interocular (Interpupillary) Distance -- the distance between the two axis of the two cameras/eyes -- 65mm is the average distance between the adult male eyes
• Stereo Base -- distance between the two cameras
• Interaxial Distance -- variable distance between two cameras
  • Hyperstereo -- >65mm
  • Orthostereo -- 65mm
  • Hypostereo -- <65mm
• Parallax -- difference when perceiving the same scene and the same object from different perspective (simply - where the object is in space relative to the screen)
  • Positive Parallax - the object appears behind the screen (Screen Space)
  • Zero Parallax - the object appears on the screen
  • Negative Parallax - the object appears in front of the screen (Audience Space)
• Crosstalk -- when one eyes sees something that is meant for the other eye
  • Contrast can strongly affect this effect
• Pinning / Edge Violation -- when the object comes into viewer space and is then cut off by the edge of the scree; it causes discomfort along the edges
• Pseudostereoscopic -- when the left and right eye images are reversed
• Very uncomfortable
• If you flip your glasses, it should fix this error
• It can create a weird/false sense of depth
• Channel Synchronization -- when one eye's image is not matched up with the other's image; when you see a frame that is ahead or behind of the other frame
• Channel Alignment -- the two images are not horizontally aligned; the images are not "even"
• Horizontal Image Translation (HIT) -- changing the offset of the stereo pair to change the "position" of the viewing screen
• Floating Window -- a post process done to help alleviate pinning on the edges of the frame - using a mask on the sides of the frame with one eye that will "crop" the edges, helping the eyes/brain to merge the "adjusted" edges
• you bring in the bar/mask on the right on only the right eye image
• you bring in the bar/mask on the left on only the left eye image

Physiological Depth Cues

• Eye Movement
• Duction -- single eye movement
• Version -- both eyes move in the same direction
• Vergence -- two eyes move in opposite directions
• Convergence - eyes move together (cross eyes)
• Divergence - eyes move apart (it hurts a LOT)
• Accommodation -- reconfiguration of the eye's lens based upon the contraction of the muscles in the eye (ciliary muscles)
• this doesn't change for the stereo illusion - the eyes don't refocus
• this effect is not directly connected to vergence
• the "auto focus" or readjusting of the eyes
• Binocular Disparity -- each eye sees a slightly different image

Psychological Depth Cues

• Retinal Angle -- larger objects take up more space in the image
• Linear Perspective -- foreshortening of objects with perspective
• Texture Gradient -- "merging" of textural detail over distance; you see more detail close up
• Aerial (Atmospheric) Perspective -- the fog or haze over distance
• Interposition (or Occlusion) -- the "overlapping" of objects; the objects you see is entirely is in front of the other
• Motion Parallax -- the things that are the closest to you move the quickest and are blurred, while the objects that are further from the camera move slower

"Artificial" Depth Cue - Ken Huff's cue

• Depth of Field

Camera Rigs