panoramas-and-multiperspective

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					                    Panorama Photography and
                     Multiperspective Imaging




Szymon Rusinkiewicz, Tim Weyrich: Technology in Art and Cultural Heritage.
Princeton Freshman Seminar 2006
Acknowledgment: some figures by B. Brown, P. Shilane, P. Debevec, A. Román and H. Lentsch
                   Overview

• Limitations of perspective projection
• Cylindrical panoramas
• Spherical panoramas
• Multiperspective imaging
   Limitations of Perspective Projection

• Field-of-view — lack of immersion
   Limitations of Perspective Projection

• Field-of-view — lack of immersion
• Wide-angle imaging
  – Potential distortion
  – Extreme perspective does not look ―natural‖
            Extreme Wide-Angle

• Up to 185° field-of-view
• Technically demanding
• Prone to distortion and
  vignetting
   Limitations of Perspective Projection

• Field-of-view — lack of immersion
• Wide-angle imaging
  – Potential distortion
  – Extreme perspective does not look ―natural‖
• Viewer position fixed
       Changing Position of Viewer

• In real scenes we can
  move our viewpoint
• Changing viewpoint
  provides us with
  – Additional detail
  – Depth cues by parallaxis
            Cylindrical Panoramas

• Address the problem of
  – Limited field-of-view
  – Distortion of wide-angle perspective
• Replace projection plane by cylindrical
  canvas:
Cylindrical Panoramas
             Panorama Paintings

• Large canvases
• Sometimes within
  cylindrical building
• Augmentation by
  scenery in front of
  the painting




                         Bourbaki Panorama, Luzern, 1871
            Panorama Acquisition

• Multiple images
  – Rotating camera
  – Ideally: very thin stripe images
• Panorama by stitching
  images together
• Requires common
  center of projection
                           Stitching

• Problems remain
   – Lens distortion
   – ―Wrong‖ projection within each image
   – Differences in color and contrast
• Stitching software
   –   Compensates for lens distortion
   –   Aligns images (registration)
   –   Warps images into cylindrical domain
   –   Smoothes out image boundaries
   –   Adapts color and contrast
            Catadioptric Cameras

• Mirror optics
• Single-shot acquisition
  of hemispherical
  panorama
• Raw image shows
  distortion…
            Catadioptric Cameras

• Desired projection is obtained by un-distorting
  the acquired image
• This includes cylindrical projection:
               Viewing Software

• Presents panorama as a perspective view
• Interactive change of viewing parameters
   – Pan
   – Zoom
• Still restricted to single view-point
• Commercial and free viewers exists
   – Quicktime VR, Live Picture Viewer, …
              Spherical Panoramas

• Restrictions of cylindrical projection remain
   – Depiction of the ―poles‖ (floor and ceiling)
   – Fixed view-point
• How would we capture floor and ceiling?
   – Acquisition?
   – Representation?
              Spherical Acquisition

• Stitching
• Or: take an image of
  a mirrored sphere!
             Representations




Spherical reflection    Projection onto cube faces
      Viewing Spherical Panoramas

• Most viewers support spherical panoramas
• Un-warp depending on representation




                 Live Demo
          Multiperspective Imaging

• Artist create multiperspective paintings
• Can we acquire multiperspective images?
          Multiperspective Imaging

• Experiment:
  – Place a person on a revolving chair
  – Take a video of the head while person is revolving
  – From each video image, take central pixel column
  – Glue all columns together
• What do you get?
Multiperspective Imaging
         Multiperspective Imaging

• Can you modify a pinhole camera to create
  such an image?
• How do images look for general movements
  of the video camera?
Multiperspective Imaging
Multiperspective Imaging
                Pushbroom

• Fix the camera on a moving vehicle
• Has been used to create movie back-drops
                 Relation To Perspective Images

                          Rays across
                          top of image




                                          Single-point
                                          Perspective Image




Center of
projection

        Picture Surface             Ray directions on image corners
              Relation To Perspective Images




                                   Pushbroom
                                   multiperspective image




Camera path
Cross-slits Images   [Zomet 03 ]
Cross-slits Images




         Camera path
Cross-slits Images




         Camera path
             Cross-slits Camera

• Replace pinhole by two slits




• Or simulate it using a video camera…
             Cross-slits Images

• Cross-slits images [Zomet 03]




                                  Zomet 2003
               Cross-slits Images

• Appearance similar to central perspective
• Allow for ―impossible viewpoints‖




  Zomet 2003
    Generating Cross-slits Panoramas

• Work by A. Roman et al. 2004 & 2006




                   Video

				
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