Layered Depth Images

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Layered Depth Images
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Choosing Sprites

• Planar Sprites
• Sprites with Depth
• Layered Depth Images
• Polygonal Sprites

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Layered Depth Images

• DepthPixel
• RGBA, Z
• Depth Image
• Camera, DepthPixelwidth,height
• LayeredDepthPixel
• numLayers, DepthPixelnumLayers
• LayeredDepthImage
• Camera, LayeredDepthPixelwidth,height

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Generating LDIs

• From a model
• Depth Images, Modified Ray Tracing
• From the real world
• Correspondence, Laser Range Finder

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Rendering LDIs

• Transformation for novel views
• C1 and C2 are the two camera matrices
• Splatting
• Size d1/d2
• Alpha approximate Gaussian

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LDI Results

• Time
• Pentium II, 300 MHz, 320 MB ram
• 320x320 pixels
• 8-10 frames/second
• By Moores Law 256-320 frames/second today
• Pretty pictures

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Layered Depth Images
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LDI Demo
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LDI Tree

• Improve sampling resolution
• Progressive Refinement
• Gap filling
• Interested in accuracy not run-time

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What is an LDI tree?

• Octree
• Tree-nodes
• BoundingBox
• Children8
• LayeredDepthImage

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Building an LDI Tree

• Same Sources
• Which tree node gets each pixel
• PixelCenter
• C is the cameras center of projection in World
  space
• a and b are the basis vectors for the image plane
• c is the viewing direction
• d is 1/z (the distance from the viewing plane)
• SplatSize
• Splat is an alpha Gaussian
• Size determines which level of the Octree

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Building an LDI Tree

• Unfiltered pixels
• Pixel placed in scale appropriate tree-node
• Filtered pixels
• Pixel is splatted into all ancestor node LDIs

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Building an LDI Tree

• For each reference image
• For each pixel
• Calculate pixel center
• Calculate splat
• Recursively descend octree to appropriate res
• Splat filtered pixel into each LDI
• Splat unfiltered pixel into appropriate res
  tree-node

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Rendering an LDI tree

• Recursive Render
• Render (Tree-Node)
• 1. If outside of view frustum return
• 2. Estimate size of the splats
• 3. If need higher-res or viewer inside bounding
  box
• 4. Call Render() recursively for each child
• 5. Warp unfiltered pixels to the Output buffer
• 6. else
• 7. Warp all pixels in LDI to the output buffer

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Rendering an LDI tree

• Hierarchy destroys LDI depth ordering
• Output Buffer is another LDI
• Render Output Buffer by splatting to screen

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Progressive Refinement

• This should be obvious

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Gap Filling

• First Pass
• Render as usual
• Create a stencil for gaps
• Second Pass
• Render filtered pixels (low res version) in the
  stencil bottom up updating the stencil

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LDI Tree Video