1. Order-Independent Texture Synthesis Li-Yi Wei Marc Levoy Gcafe 1/30/2003

2. 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

3. 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

4. New Algorithm Key Ideas: –multiple generations –neighborhood contains only old values lower generations, lower resolutions –pyramidal cache Details: –see the paper (4 pages only)☺

5. Example Generation 2Generation 1Generation 0

6. Example Level 3 Level 2 Level 1 Level 0 Generation 2Generation 1Generation 0

7. Single Polygon RenderingMipmap Texture 19% requested 23% computed

8. Quake Texture 64  64 Unnatural repetition Texture 512  512 Less repetition

9. Ray Casting SceneTexture

10. Simulation Result

11. Future Work Implementation as fragment shader☻

12. End

14. Overview Procedurally Statistical Texture Synthesis –algorithm –architecture Applications –procedural shader –interactive tools –texture mapping hardware

15. Texture Mapping Bottleneck in graphics pipeline –computation –texture memory access Solutions –caching –pre-fetching –compression [VQ] texture image

16. Texture Synthesis Input Result Texture Mapping Compression

17. How It Works noise Input pyramid noise Output pyramid Search Copy

18. Goal Combine advantages from both camps –general –independent texel evaluation

19. 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

20. Problem with Old Algorithm dependency graph cycles in the dependency graph! level row col 0 -1 0 0 +1 0 0 0 -1 0 0 +1 -1 0 0

21. New Algorithm level row col generation 0 -1 0 -1 0 +1 0 -1 0 0 -1 -1 0 0 +1 -1 -1 0 0 newest dependency graph Keep multiple generations Acyclic dependency graph Order-independent evaluation

22. Implementation : Cache no full pyramid required, use cache instead output determined solely by lowest resolution

23. Algorithm level row col generation L x-1 y g-1 L x+1 y g-1 L x y-1 g-1 L x y+1 g-1 L-1 x y g evaluate (level=L, row = x, col = y, generation = g) Cached? evaluate (L, x-1, y, g-1) 2. Collect neighborhood 3. Find best match 1. If in cache, return it

24. Cache Footprint : Single Pixel Level 3Level 2Level 1Level 0 Generation 2 Generation 1 Generation 0

25. Cache Footprint : S Level 3Level 2Level 1Level 0 Generation 2 Generation 1 Generation 0

26. Cache Footprint : Sphere Level 3Level 2Level 1Level 0 Generation 2 Generation 1 Generation 0

27. Cache Footprint : Random Level 3Level 2Level 1Level 0 Generation 2 Generation 1 Generation 0

28. Cache Footprint: Single Pixel Level 3 Level 2 Level 1 Level 0 Generation 2Generation 1Generation 0 1148 pixels!

29. Cache Footprint: Poisson Points Level 3 Level 2 Level 1 Level 0 Generation 2Generation 1Generation 0

30. Cache Footprint: Circular Pattern Level 3 Level 2 Level 1 Level 0 Generation 2Generation 1Generation 0

31. Cache Usage Statistics Percentage of input requested Percentage of cache used random sphere ideal (linear)

32. Cache Coherence

33. Quality Comparison oldnew

34. Quake Texture 64  64Texture 512  512 Input 44% requested 48% computed

35. QuickTime VR OriginalResult Input invisible

36. Simulation Result

37. Architecture Design

38. Pitfalls not feasible for current hardware can only be applied to repeating patterns

39. Finished Work Verification using an infinite cache

40. 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

42. Motivation Texture mapping is important Texture mapping can be a bottleneck Solution: Texture Mapping by Synthesis

43. Hardware Trend  Computation >>  Memory Speed Transform memory access into computation