1. 1 Rendering Transitions in a Geometric Level of Detail Framework Defended by Shaun David Ramsey On July 27, 2004

2. 2/41 Outline  Motivation - Hierarchy of Structure  Contributions Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques  Results

3. 3/41 Video Generation  Large amount of detail dependent on viewing angle, and viewing location

4. 4/41 Rendering Structure Macro Meso Micro

5. 5/41 Geometry  Mesh Sizes continue to grow  Varied Representations

6. 6/41 Simplification

7. 7/41 Level of Detail Hierarchies

8. 8/41 Progressive Meshes  Level Of Detail Hierarchy Edge Collapse Texture Mapping

9. 9/41 What’s Missing?  Mesostructure Displacement maps Bump maps  Microstructure BRDFs  Algorithms to utilize Rendering Methods

10. 10/41 What’s Missing? BRDFs

11. 11/41 What’s Missing? Bump Maps

12. 12/41 What’s Missing? Displacement Maps

13. 13/41 What’s Missing? Rendering Transitions  Construct BRDFs, bump maps and displacement maps with consistent intensities  Redistributed bump mapping algorithm Becker and Max 1993

14. 14/41 Spanning the Gap  Combine simplifications for meso-, micro- and macrostructure  Incorporate view-dependent rendering techniques in a geometric level of detail framework.

15. 15/41 Outline  Motivation - Hierarchy of Structure  Contributions Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques  Results

16. 16/41 Arbitrary Polyhedral Simplification  Edge collapses for arbitrary polyhedra Ramsey, Bertram, and Hansen [CGIM 2003]

17. 17/41 Normal Deviation  Use normal deviation to drive simplification  Complicated records for APS

18. 18/41 Changing Thresholds OriginalSimplifiedSimplified 21590 polys5600 polys5600 polys cos=0.95cos=0.0

19. 19/41 Outline  Motivation - Hierarchy of Structure  Contributions Arbitrary Polyhedral Simplification Structure Combination (Rendering+LOD) Ray Tracing Techniques (BPs, Disp PMs)  Results

20. 20/41 Structure Combination  Rendering System required to glue pieces together Ray Tracing Bilinear Patches for Normal Distributions (BRDFs, RBM) Ray Tracing Displaced Progressive Meshes (Combines LOD with Appearance)

21. 21/41 Rendering Transitions  Becker [1992] and Becker and Max [1993]  Construct BRDFs and RBMs from normal distributions  Transition between BRDFs, RBMs (interpolation) and between RBMs and displacement maps (partial bumps)

22. 22/41 Construct Normal Distributions  Ray Trace displaced plane with scalar height field (why not use bilinear patches)

23. 23/41 Bilinear Patches  Eliminate Bias

24. 24/41 Ray Tracing Bilinear Patches  Bilinear Patches [Ramsey, Potter, Hansen JGT 2004]  P(t) = r + t q  P(u,v) = (1-u)(1-v) p 00 + (1-u)v p 01 + u(1-v) p 10 + uv p 11 = a uv + b u + c v + d  Solve P(u,v) = P(t)

25. 25/41 Quadratics  Reduce numerical error and instability

26. 26/41 Efficiency  790m intersection tests Ray-Bilinear Patches 754s (1.05m tests/s) Two Plane-Bilinear Patches 963s (0.82m tests/s)

27. 27/41 Ray Traced PMs with Rendering Transitions  General Algorithm with Discrete LOD Determine LOD L i to use (d) Ray Trace L i Determine Rendering Method (d,  ) If Displaced or Partial Bump, ray trace Else compute intensity from BRDF and RBM

28. 28/41 Negative Displacements d -d

29. 29/41 Transitioned Displacements  Partial bumps with negative displacements

30. 30/41 Ray Tracing Displacements  Many levels of 4-to-1 subdivision  Pass proportion to each triangle

31. 31/41 Contributions  Arbitrary Polyhedral Simplification  Rendering (Ray Tracing): Bilinear Patch Intersections Displaced Progressive Meshes Rendering Transitions  Combining Rendering Transitions in a Geometric Level of Detail Framework

32. 32/41 Outline  Motivation - Hierarchy of Structure  Contributions Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques  Results

33. 33/41 Effect of Subdivision Level l=1, *4 l=2, *16 l=3, *64 l=4,*256 l=5, *1024 l describes subdivision level, * describes triangles rendered per original triangle in the model

34. 34/41 Results - transitions Disp are green Bumps are blue BRDFs are red

35. 35/41 Results – changing LOD 4500 polys 3500 polys 3500 polys 2500 polys 2500 polys 1500 polys 1500 polys 500 polys

36. 36/41 Results – user params  Change transitions, change PMs, heights Disp are greenBumps are blueBRDFs are red

37. 37/41 Results - Movies  Displaced Movie - Scintillation  Color Movie – when transitions are used  Rendered Movie – the full LOD/transition system

38. 38/41 Rendering Times Rendering Method Mesh 0.33s0.11s0.38s BRDF 0.40s0.11s0.45s RBM 3.70s1.40s3.99s Displaced Detailed 24.95s5.09s41.52s LOD Transition System 3.70s1.33s31.28s

39. 39/41 Future Work  Shadows  Displacement map rendering  Distributed Ray Tracing

40. 40/41 Other Rendering Techniques  Realistic Materials Subsurface scattering BRDFs (anisotropy, specularity)  Replace the BRDF with Bitextures  Hardware (VDMs)

41. 41/41 The End Questions?