OrderIndependent Texture Synthesis

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Order-Independent Texture Synthesis

• Li-Yi Wei Marc Levoy

Gcafe 1/30/2003
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Previous Work

• Statistical Synthesis
• general, requires only a sample
• cannot be evaluated randomly on the fly
• Procedural Synthesis
• evaluation on the fly (e.g. Perlin noise)
• efficient
• less general, hard to set parameters

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Goal

• Combine Advantages from both Camps
• general as statistical methods
• generate new textures from a given example
• flexible as procedural methods
• evaluate texels on demand
• result always identical regardless of evaluation
  order

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New Algorithm

• Key Ideas
• multiple generations
• neighborhood contains only old values
• lower generations, lower resolutions
• pyramidal cache
• Details
• see the paper (4 pages only)?

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Example
Generation 2
Generation 1
Generation 0
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Example
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Single Polygon
19 requested 23 computed
Rendering
Mipmap Texture
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Quake
Texture 64 ? 64 Unnatural repetition
Texture 512 ? 512 Less repetition
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Ray Casting
Scene
Texture
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Simulation Result
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Future Work

• Implementation as fragment shader?

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End
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Overview

• Procedurally Statistical Texture Synthesis
• algorithm
• architecture
• Applications
• procedural shader
• interactive tools
• texture mapping hardware

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Texture Mapping

• Bottleneck in graphics pipeline
• computation
• texture memory access
• Solutions
• caching
• pre-fetching
• compression VQ

texture
image
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Texture Synthesis
Texture Synthesis
Input
Result
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How It Works
noise
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Goal

• Combine advantages from both camps
• general
• independent texel evaluation

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Order-Independent Texture Synthesis

• Simple modifications of our old algorithm
• evaluate pixel in any order
• consistent result (given the same initial value)
• time complexity depends only on neighborhood size
  (not on output texture size)
• interface much like procedural synthesis
• greater flexibility
• more computation

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Problem with Old Algorithm
dependency graph
level row col 0 -1 0 0 1 0
0 0 -1 0 0 1 -1
0 0
cycles in the dependency graph!
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New Algorithm
dependency graph
Keep multiple generations Acyclic dependency graph
level row col generation 0 -1 0 -1
0 1 0 -1 0 0 -1 -1 0
0 1 -1 -1 0 0 newest
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Implementation Cache

• no full pyramid required, use cache instead
• output determined solely by lowest resolution

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Algorithm
evaluate (levelL, row x, col y, generation
g)
1. If in cache, return it
2. Collect neighborhood
level row col generation L x-1 y
g-1 L x1 y g-1 L x y-1
g-1 L x y1 g-1 L-1 x y g
Cached?
evaluate (L, x-1, y, g-1)
3. Find best match
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Cache Footprint Single Pixel
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Cache Footprint S
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Cache Footprint Sphere
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Cache Footprint Random
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Cache Footprint Single Pixel
1148 pixels!
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Cache FootprintPoisson Points
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Cache FootprintCircular Pattern
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Cache Usage Statistics
random
sphere
Percentage of cache used
ideal (linear)
Percentage of input requested
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Cache Coherence
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Quality Comparison
old
new
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Quake
44 requested 48 computed
Input
Texture 64 ? 64
Texture 512 ? 512
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QuickTime VR
invisible
Input
Original
Result
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Simulation Result
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Architecture Design
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Pitfalls

• not feasible for current hardware
• can only be applied to repeating patterns

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Finished Work

• Verification using an infinite cache

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Ongoing Work

• Measuring and understanding various parameters
• cache size, associativity, replacement policy
• evaluation order for missing pixels (register
  allocation)
• benchmarking
• Combination with patch-based texture synthesis
• patch boundaries?
• complicate caching behavior

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Motivation

• Texture mapping is important
• Texture mapping can be a bottleneck
• Solution Texture Mapping by Synthesis

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Hardware Trend

• ? Computation gtgt ? Memory Speed
• Transform memory access into computation