Quick Time VR

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Quick Time VR An Image-Based
Approach to Virtual Environment Navigation
By Shenchang Eric Chen, Lance Williams
Apple Computer, Inc.
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Cons 1- Only 3 degrees of freedom (plus zoom)
(you can point the camera in any direction,
but you can't move the camera) 2- Scenes must be
static (you can do looping animations, but
user-controlled objects don't work well) 3-
Storage requirements can be large
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Pros 1- Rendering time is proportional to view
size, not scene complexity. 2- No special 3D
hardware is necessary for reasonable
performance with real-time rendering. 3-
Rendering is just a simple warping of a portion
of the full image.
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• Memory Usage
• Environment maps are diced into tiles to optimize
  memory page usage
• Each tile is converted to a MipMap to reduce
  swapping irrespective of zoom
• Finally the tiles are compressed

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• QuickTime specific stuff
• 3 Tracks -- Node with links to other nodes,
  Environment map (the scene), Hot spot masks
• Support for object rotation (orbiting camera)
• Event driven interaction follows link to another
  node when a hot-spot is clicked

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View Interpolation for Image Synthesis By
Shenchang Eric Chen, Lance Williams Apple
Computer, Inc.
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Interpolation requires d 1 images where d is
the number of degrees of freedom that the camera
has. For QTVR, the camera only needs 3 degrees
of freedom (because the other 3 are implicitly
handled) Linear weights for each image are
computed to sum to 1. (Linear interpolation)
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• Primary objective is performance
• Correspondence maps are precomputed between every
  pair of images.
• Maps every source pixel to a destination location
• Maps are needed in both directions due to holes
• Stored as vector offsets
• Grouped into quadtree blocks
• Interpolation is computed for entire block at a
  time
• Blocks are sorted by their average source image z
  value and displayed back to front in order to
  handle occlusions without the overhead of a
  z-buffer

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Holes
Interpolated from neighbor pixels
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Motion Blur Jerky motion caused by instant
sampling--aliasing in temporal domain Fixed by
supersampling over time and averaging images
together
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Shadows First render shadows from two or more
light sources Compute morph-map only for
shadows Interpolate shadows from other light
sources
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